/*

  * MPEG-4 decoder

  * Copyright (c) 2000,2001 Fabrice Bellard
  * Copyright (c) 2002-2010 Michael Niedermayer <michaelni@gmx.at>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 

 #define UNCHECKED_BITSTREAM_READER 1
 

 #include "libavutil/internal.h"

 #include "libavutil/opt.h"

 #include "error_resilience.h"

 #include "hwaccel.h"

 #include "idctdsp.h"

 #include "internal.h"

 #include "mpegutils.h"

 #include "mpegvideo.h"

 #include "mpegvideodata.h"

 #include "mpeg4video.h"
 #include "h263.h"

 #include "profiles.h"

 #include "thread.h"

 #include "xvididct.h"

 /* The defines below define the number of bits that are read at once for
  * reading vlc values. Changing these may improve speed and data cache needs
  * be aware though that decreasing them may need the number of stages that is
  * passed to get_vlc* to be increased. */

 #define SPRITE_TRAJ_VLC_BITS 6
 #define DC_VLC_BITS 9
 #define MB_TYPE_B_VLC_BITS 4

 #define STUDIO_INTRA_BITS 9

 
 static VLC dc_lum, dc_chrom;
 static VLC sprite_trajectory;
 static VLC mb_type_b_vlc;
 

 static const int mb_type_b_map[4] = {

     MB_TYPE_DIRECT2 | MB_TYPE_L0L1,

     MB_TYPE_L0L1    | MB_TYPE_16x16,
     MB_TYPE_L1      | MB_TYPE_16x16,
     MB_TYPE_L0      | MB_TYPE_16x16,

 };
 
 /**

  * Predict the ac.

  * @param n block index (0-3 are luma, 4-5 are chroma)
  * @param dir the ac prediction direction
  */

 void ff_mpeg4_pred_ac(MpegEncContext *s, int16_t *block, int n, int dir)

 {
     int i;
     int16_t *ac_val, *ac_val1;

     int8_t *const qscale_table = s->current_picture.qscale_table;

 
     /* find prediction */

     ac_val  = &s->ac_val[0][0][0] + s->block_index[n] * 16;

     ac_val1 = ac_val;
     if (s->ac_pred) {
         if (dir == 0) {

             const int xy = s->mb_x - 1 + s->mb_y * s->mb_stride;

             /* left prediction */
             ac_val -= 16;
 

             if (s->mb_x == 0 || s->qscale == qscale_table[xy] ||
                 n == 1 || n == 3) {

                 /* same qscale */

                 for (i = 1; i < 8; i++)

                     block[s->idsp.idct_permutation[i << 3]] += ac_val[i];

             } else {

                 /* different qscale, we must rescale */

                 for (i = 1; i < 8; i++)

                     block[s->idsp.idct_permutation[i << 3]] += ROUNDED_DIV(ac_val[i] * qscale_table[xy], s->qscale);

             }
         } else {

             const int xy = s->mb_x + s->mb_y * s->mb_stride - s->mb_stride;

             /* top prediction */
             ac_val -= 16 * s->block_wrap[n];
 

             if (s->mb_y == 0 || s->qscale == qscale_table[xy] ||
                 n == 2 || n == 3) {

                 /* same qscale */

                 for (i = 1; i < 8; i++)

                     block[s->idsp.idct_permutation[i]] += ac_val[i + 8];

             } else {

                 /* different qscale, we must rescale */

                 for (i = 1; i < 8; i++)

                     block[s->idsp.idct_permutation[i]] += ROUNDED_DIV(ac_val[i + 8] * qscale_table[xy], s->qscale);

             }
         }
     }
     /* left copy */

     for (i = 1; i < 8; i++)

         ac_val1[i] = block[s->idsp.idct_permutation[i << 3]];

 
     /* top copy */

     for (i = 1; i < 8; i++)

         ac_val1[8 + i] = block[s->idsp.idct_permutation[i]];

 }
 
 /**
  * check if the next stuff is a resync marker or the end.
  * @return 0 if not
  */

 static inline int mpeg4_is_resync(Mpeg4DecContext *ctx)

 {

     MpegEncContext *s = &ctx->m;

     int bits_count = get_bits_count(&s->gb);
     int v          = show_bits(&s->gb, 16);

     if (s->workaround_bugs & FF_BUG_NO_PADDING && !ctx->resync_marker)

         return 0;
 

     while (v <= 0xFF) {
         if (s->pict_type == AV_PICTURE_TYPE_B ||
             (v >> (8 - s->pict_type) != 1) || s->partitioned_frame)

             break;

         skip_bits(&s->gb, 8 + s->pict_type);
         bits_count += 8 + s->pict_type;
         v = show_bits(&s->gb, 16);

     }
 

     if (bits_count + 8 >= s->gb.size_in_bits) {
         v >>= 8;
         v  |= 0x7F >> (7 - (bits_count & 7));

         if (v == 0x7F)

             return s->mb_num;

     } else {
         if (v == ff_mpeg4_resync_prefix[bits_count & 7]) {

             int len, mb_num;

             int mb_num_bits = av_log2(s->mb_num - 1) + 1;

             GetBitContext gb = s->gb;

 
             skip_bits(&s->gb, 1);
             align_get_bits(&s->gb);
 

             for (len = 0; len < 32; len++)
                 if (get_bits1(&s->gb))
                     break;

             mb_num = get_bits(&s->gb, mb_num_bits);
             if (!mb_num || mb_num > s->mb_num || get_bits_count(&s->gb)+6 > s->gb.size_in_bits)

                 mb_num= -1;
 

             s->gb = gb;

             if (len >= ff_mpeg4_get_video_packet_prefix_length(s))

                 return mb_num;

         }
     }
     return 0;
 }
 

 static int mpeg4_decode_sprite_trajectory(Mpeg4DecContext *ctx, GetBitContext *gb)

 {

     MpegEncContext *s = &ctx->m;

     int a     = 2 << s->sprite_warping_accuracy;
     int rho   = 3  - s->sprite_warping_accuracy;
     int r     = 16 / a;

     int alpha = 1;

     int beta  = 0;
     int w     = s->width;
     int h     = s->height;
     int min_ab, i, w2, h2, w3, h3;

     int sprite_ref[4][2];
     int virtual_ref[2][2];

     int64_t sprite_offset[2][2];

     int64_t sprite_delta[2][2];

 
     // only true for rectangle shapes
     const int vop_ref[4][2] = { { 0, 0 },         { s->width, 0 },
                                 { 0, s->height }, { s->width, s->height } };
     int d[4][2]             = { { 0, 0 }, { 0, 0 }, { 0, 0 }, { 0, 0 } };

     if (w <= 0 || h <= 0)
         return AVERROR_INVALIDDATA;

     /* the decoder was not properly initialized and we cannot continue */
     if (sprite_trajectory.table == NULL)
         return AVERROR_INVALIDDATA;
 

     for (i = 0; i < ctx->num_sprite_warping_points; i++) {

         int length;

         int x = 0, y = 0;

         length = get_vlc2(gb, sprite_trajectory.table, SPRITE_TRAJ_VLC_BITS, 3);

         if (length > 0)

             x = get_xbits(gb, length);

         if (!(ctx->divx_version == 500 && ctx->divx_build == 413))

             check_marker(s->avctx, gb, "before sprite_trajectory");

 
         length = get_vlc2(gb, sprite_trajectory.table, SPRITE_TRAJ_VLC_BITS, 3);

         if (length > 0)

             y = get_xbits(gb, length);
 

         check_marker(s->avctx, gb, "after sprite_trajectory");

         ctx->sprite_traj[i][0] = d[i][0] = x;
         ctx->sprite_traj[i][1] = d[i][1] = y;

     }

     for (; i < 4; i++)

         ctx->sprite_traj[i][0] = ctx->sprite_traj[i][1] = 0;

 
     while ((1 << alpha) < w)
         alpha++;
     while ((1 << beta) < h)

         beta++;  /* typo in the MPEG-4 std for the definition of w' and h' */

     w2 = 1 << alpha;
     h2 = 1 << beta;
 
     // Note, the 4th point isn't used for GMC

     if (ctx->divx_version == 500 && ctx->divx_build == 413) {

         sprite_ref[0][0] = a * vop_ref[0][0] + d[0][0];
         sprite_ref[0][1] = a * vop_ref[0][1] + d[0][1];
         sprite_ref[1][0] = a * vop_ref[1][0] + d[0][0] + d[1][0];
         sprite_ref[1][1] = a * vop_ref[1][1] + d[0][1] + d[1][1];
         sprite_ref[2][0] = a * vop_ref[2][0] + d[0][0] + d[2][0];
         sprite_ref[2][1] = a * vop_ref[2][1] + d[0][1] + d[2][1];

     } else {

         sprite_ref[0][0] = (a >> 1) * (2 * vop_ref[0][0] + d[0][0]);
         sprite_ref[0][1] = (a >> 1) * (2 * vop_ref[0][1] + d[0][1]);
         sprite_ref[1][0] = (a >> 1) * (2 * vop_ref[1][0] + d[0][0] + d[1][0]);
         sprite_ref[1][1] = (a >> 1) * (2 * vop_ref[1][1] + d[0][1] + d[1][1]);
         sprite_ref[2][0] = (a >> 1) * (2 * vop_ref[2][0] + d[0][0] + d[2][0]);
         sprite_ref[2][1] = (a >> 1) * (2 * vop_ref[2][1] + d[0][1] + d[2][1]);

     }

     /* sprite_ref[3][0] = (a >> 1) * (2 * vop_ref[3][0] + d[0][0] + d[1][0] + d[2][0] + d[3][0]);
      * sprite_ref[3][1] = (a >> 1) * (2 * vop_ref[3][1] + d[0][1] + d[1][1] + d[2][1] + d[3][1]); */
 

     /* This is mostly identical to the MPEG-4 std (and is totally unreadable

      * because of that...). Perhaps it should be reordered to be more readable.
      * The idea behind this virtual_ref mess is to be able to use shifts later
      * per pixel instead of divides so the distance between points is converted
      * from w&h based to w2&h2 based which are of the 2^x form. */
     virtual_ref[0][0] = 16 * (vop_ref[0][0] + w2) +
                          ROUNDED_DIV(((w - w2) *

                                            (r * sprite_ref[0][0] - 16LL * vop_ref[0][0]) +
                                       w2 * (r * sprite_ref[1][0] - 16LL * vop_ref[1][0])), w);

     virtual_ref[0][1] = 16 * vop_ref[0][1] +
                         ROUNDED_DIV(((w - w2) *

                                           (r * sprite_ref[0][1] - 16LL * vop_ref[0][1]) +
                                      w2 * (r * sprite_ref[1][1] - 16LL * vop_ref[1][1])), w);

     virtual_ref[1][0] = 16 * vop_ref[0][0] +

                         ROUNDED_DIV(((h - h2) * (r * sprite_ref[0][0] - 16LL * vop_ref[0][0]) +
                                            h2 * (r * sprite_ref[2][0] - 16LL * vop_ref[2][0])), h);

     virtual_ref[1][1] = 16 * (vop_ref[0][1] + h2) +

                         ROUNDED_DIV(((h - h2) * (r * sprite_ref[0][1] - 16LL * vop_ref[0][1]) +
                                            h2 * (r * sprite_ref[2][1] - 16LL * vop_ref[2][1])), h);

     switch (ctx->num_sprite_warping_points) {

     case 0:

         sprite_offset[0][0]    =
         sprite_offset[0][1]    =
         sprite_offset[1][0]    =
         sprite_offset[1][1]    = 0;

         sprite_delta[0][0]     = a;
         sprite_delta[0][1]     =
         sprite_delta[1][0]     = 0;
         sprite_delta[1][1]     = a;

         ctx->sprite_shift[0]   =
         ctx->sprite_shift[1]   = 0;

         break;
     case 1:     // GMC only

         sprite_offset[0][0]    = sprite_ref[0][0] - a * vop_ref[0][0];
         sprite_offset[0][1]    = sprite_ref[0][1] - a * vop_ref[0][1];
         sprite_offset[1][0]    = ((sprite_ref[0][0] >> 1) | (sprite_ref[0][0] & 1)) -

                                  a * (vop_ref[0][0] / 2);

         sprite_offset[1][1]    = ((sprite_ref[0][1] >> 1) | (sprite_ref[0][1] & 1)) -

                                  a * (vop_ref[0][1] / 2);

         sprite_delta[0][0]     = a;
         sprite_delta[0][1]     =
         sprite_delta[1][0]     = 0;
         sprite_delta[1][1]     = a;

         ctx->sprite_shift[0]   =
         ctx->sprite_shift[1]   = 0;

         break;
     case 2:

         sprite_offset[0][0]    = ((int64_t)      sprite_ref[0][0] * (1 << alpha + rho)) +
                                  ((int64_t) -r * sprite_ref[0][0] + virtual_ref[0][0]) *
                                  ((int64_t)        -vop_ref[0][0]) +
                                  ((int64_t)  r * sprite_ref[0][1] - virtual_ref[0][1]) *
                                  ((int64_t)        -vop_ref[0][1]) + (1 << (alpha + rho - 1));
         sprite_offset[0][1]    = ((int64_t)      sprite_ref[0][1] * (1 << alpha + rho)) +
                                  ((int64_t) -r * sprite_ref[0][1] + virtual_ref[0][1]) *
                                  ((int64_t)        -vop_ref[0][0]) +
                                  ((int64_t) -r * sprite_ref[0][0] + virtual_ref[0][0]) *
                                  ((int64_t)        -vop_ref[0][1]) + (1 << (alpha + rho - 1));
         sprite_offset[1][0]    = (((int64_t)-r * sprite_ref[0][0] + virtual_ref[0][0]) *
                                   ((int64_t)-2 *    vop_ref[0][0] + 1) +
                                   ((int64_t) r * sprite_ref[0][1] - virtual_ref[0][1]) *
                                   ((int64_t)-2 *    vop_ref[0][1] + 1) + 2 * w2 * r *
                                    (int64_t)     sprite_ref[0][0] - 16 * w2 + (1 << (alpha + rho + 1)));
         sprite_offset[1][1]    = (((int64_t)-r * sprite_ref[0][1] + virtual_ref[0][1]) *
                                   ((int64_t)-2 *    vop_ref[0][0] + 1) +
                                   ((int64_t)-r * sprite_ref[0][0] + virtual_ref[0][0]) *
                                   ((int64_t)-2 *    vop_ref[0][1] + 1) + 2 * w2 * r *
                                   (int64_t)      sprite_ref[0][1] - 16 * w2 + (1 << (alpha + rho + 1)));

         sprite_delta[0][0] = (-r * sprite_ref[0][0] + virtual_ref[0][0]);
         sprite_delta[0][1] = (+r * sprite_ref[0][1] - virtual_ref[0][1]);
         sprite_delta[1][0] = (-r * sprite_ref[0][1] + virtual_ref[0][1]);
         sprite_delta[1][1] = (-r * sprite_ref[0][0] + virtual_ref[0][0]);

         ctx->sprite_shift[0]  = alpha + rho;
         ctx->sprite_shift[1]  = alpha + rho + 2;

         break;
     case 3:
         min_ab = FFMIN(alpha, beta);
         w3     = w2 >> min_ab;
         h3     = h2 >> min_ab;

         sprite_offset[0][0]    = ((int64_t)sprite_ref[0][0] * (1 << (alpha + beta + rho - min_ab))) +
                                  ((int64_t)-r * sprite_ref[0][0] + virtual_ref[0][0]) * h3 * (-vop_ref[0][0]) +
                                  ((int64_t)-r * sprite_ref[0][0] + virtual_ref[1][0]) * w3 * (-vop_ref[0][1]) +
                                  ((int64_t)1 << (alpha + beta + rho - min_ab - 1));
         sprite_offset[0][1]    = ((int64_t)sprite_ref[0][1] * (1 << (alpha + beta + rho - min_ab))) +
                                  ((int64_t)-r * sprite_ref[0][1] + virtual_ref[0][1]) * h3 * (-vop_ref[0][0]) +
                                  ((int64_t)-r * sprite_ref[0][1] + virtual_ref[1][1]) * w3 * (-vop_ref[0][1]) +
                                  ((int64_t)1 << (alpha + beta + rho - min_ab - 1));
         sprite_offset[1][0]    = ((int64_t)-r * sprite_ref[0][0] + virtual_ref[0][0]) * h3 * (-2 * vop_ref[0][0] + 1) +
                                  ((int64_t)-r * sprite_ref[0][0] + virtual_ref[1][0]) * w3 * (-2 * vop_ref[0][1] + 1) +
                                   (int64_t)2 * w2 * h3 * r * sprite_ref[0][0] - 16 * w2 * h3 +
                                  ((int64_t)1 << (alpha + beta + rho - min_ab + 1));
         sprite_offset[1][1]    = ((int64_t)-r * sprite_ref[0][1] + virtual_ref[0][1]) * h3 * (-2 * vop_ref[0][0] + 1) +
                                  ((int64_t)-r * sprite_ref[0][1] + virtual_ref[1][1]) * w3 * (-2 * vop_ref[0][1] + 1) +
                                   (int64_t)2 * w2 * h3 * r * sprite_ref[0][1] - 16 * w2 * h3 +
                                  ((int64_t)1 << (alpha + beta + rho - min_ab + 1));

         sprite_delta[0][0] = (-r * (int64_t)sprite_ref[0][0] + virtual_ref[0][0]) * h3;
         sprite_delta[0][1] = (-r * (int64_t)sprite_ref[0][0] + virtual_ref[1][0]) * w3;
         sprite_delta[1][0] = (-r * (int64_t)sprite_ref[0][1] + virtual_ref[0][1]) * h3;
         sprite_delta[1][1] = (-r * (int64_t)sprite_ref[0][1] + virtual_ref[1][1]) * w3;

         ctx->sprite_shift[0]  = alpha + beta + rho - min_ab;
         ctx->sprite_shift[1]  = alpha + beta + rho - min_ab + 2;

         break;

     }
     /* try to simplify the situation */

     if (sprite_delta[0][0] == a << ctx->sprite_shift[0] &&
         sprite_delta[0][1] == 0 &&
         sprite_delta[1][0] == 0 &&
         sprite_delta[1][1] == a << ctx->sprite_shift[0]) {

         sprite_offset[0][0] >>= ctx->sprite_shift[0];
         sprite_offset[0][1] >>= ctx->sprite_shift[0];
         sprite_offset[1][0] >>= ctx->sprite_shift[1];
         sprite_offset[1][1] >>= ctx->sprite_shift[1];

         sprite_delta[0][0] = a;
         sprite_delta[0][1] = 0;
         sprite_delta[1][0] = 0;
         sprite_delta[1][1] = a;

         ctx->sprite_shift[0] = 0;
         ctx->sprite_shift[1] = 0;

         s->real_sprite_warping_points = 1;
     } else {

         int shift_y = 16 - ctx->sprite_shift[0];
         int shift_c = 16 - ctx->sprite_shift[1];

         for (i = 0; i < 2; i++) {
             if (shift_c < 0 || shift_y < 0 ||
                 FFABS(  sprite_offset[0][i]) >= INT_MAX >> shift_y  ||
                 FFABS(  sprite_offset[1][i]) >= INT_MAX >> shift_c  ||

                 FFABS(   sprite_delta[0][i]) >= INT_MAX >> shift_y  ||
                 FFABS(   sprite_delta[1][i]) >= INT_MAX >> shift_y

             ) {
                 avpriv_request_sample(s->avctx, "Too large sprite shift, delta or offset");
                 goto overflow;
             }

         }
 

         for (i = 0; i < 2; i++) {

             sprite_offset[0][i]    *= 1 << shift_y;
             sprite_offset[1][i]    *= 1 << shift_c;

             sprite_delta[0][i]     *= 1 << shift_y;
             sprite_delta[1][i]     *= 1 << shift_y;

             ctx->sprite_shift[i]     = 16;

         }
         for (i = 0; i < 2; i++) {

             int64_t sd[2] = {

                 sprite_delta[i][0] - a * (1LL<<16),
                 sprite_delta[i][1] - a * (1LL<<16)

             };
 

             if (llabs(sprite_offset[0][i] + sprite_delta[i][0] * (w+16LL)) >= INT_MAX ||
                 llabs(sprite_offset[0][i] + sprite_delta[i][1] * (h+16LL)) >= INT_MAX ||
                 llabs(sprite_offset[0][i] + sprite_delta[i][0] * (w+16LL) + sprite_delta[i][1] * (h+16LL)) >= INT_MAX ||
                 llabs(sprite_delta[i][0] * (w+16LL)) >= INT_MAX ||
                 llabs(sprite_delta[i][1] * (w+16LL)) >= INT_MAX ||

                 llabs(sd[0]) >= INT_MAX ||
                 llabs(sd[1]) >= INT_MAX ||

                 llabs(sprite_offset[0][i] + sd[0] * (w+16LL)) >= INT_MAX ||
                 llabs(sprite_offset[0][i] + sd[1] * (h+16LL)) >= INT_MAX ||
                 llabs(sprite_offset[0][i] + sd[0] * (w+16LL) + sd[1] * (h+16LL)) >= INT_MAX

             ) {

                 avpriv_request_sample(s->avctx, "Overflow on sprite points");

                 goto overflow;

             }

         }

         s->real_sprite_warping_points = ctx->num_sprite_warping_points;

     }

     for (i = 0; i < 4; i++) {
         s->sprite_offset[i&1][i>>1] = sprite_offset[i&1][i>>1];
         s->sprite_delta [i&1][i>>1] = sprite_delta [i&1][i>>1];
     }

     return 0;

 overflow:
     memset(s->sprite_offset, 0, sizeof(s->sprite_offset));
     memset(s->sprite_delta, 0, sizeof(s->sprite_delta));
     return AVERROR_PATCHWELCOME;

 }
 

 static int decode_new_pred(Mpeg4DecContext *ctx, GetBitContext *gb) {

     MpegEncContext *s = &ctx->m;

     int len = FFMIN(ctx->time_increment_bits + 3, 15);

 
     get_bits(gb, len);
     if (get_bits1(gb))
         get_bits(gb, len);

     check_marker(s->avctx, gb, "after new_pred");

 
     return 0;
 }
 

 /**

  * Decode the next video packet.

  * @return <0 if something went wrong
  */

 int ff_mpeg4_decode_video_packet_header(Mpeg4DecContext *ctx)

 {

     MpegEncContext *s = &ctx->m;
 

     int mb_num_bits      = av_log2(s->mb_num - 1) + 1;
     int header_extension = 0, mb_num, len;

 
     /* is there enough space left for a video packet + header */

     if (get_bits_count(&s->gb) > s->gb.size_in_bits - 20)

         return AVERROR_INVALIDDATA;

     for (len = 0; len < 32; len++)
         if (get_bits1(&s->gb))
             break;

     if (len != ff_mpeg4_get_video_packet_prefix_length(s)) {

         av_log(s->avctx, AV_LOG_ERROR, "marker does not match f_code\n");

         return AVERROR_INVALIDDATA;

     }
 

     if (ctx->shape != RECT_SHAPE) {

         header_extension = get_bits1(&s->gb);
         // FIXME more stuff here

     }
 

     mb_num = get_bits(&s->gb, mb_num_bits);

     if (mb_num >= s->mb_num || !mb_num) {

         av_log(s->avctx, AV_LOG_ERROR,
                "illegal mb_num in video packet (%d %d) \n", mb_num, s->mb_num);

         return AVERROR_INVALIDDATA;

     }
 

     s->mb_x = mb_num % s->mb_width;
     s->mb_y = mb_num / s->mb_width;

     if (ctx->shape != BIN_ONLY_SHAPE) {

         int qscale = get_bits(&s->gb, s->quant_precision);
         if (qscale)
             s->chroma_qscale = s->qscale = qscale;

     }
 

     if (ctx->shape == RECT_SHAPE)

         header_extension = get_bits1(&s->gb);
 
     if (header_extension) {
         int time_incr = 0;

 
         while (get_bits1(&s->gb) != 0)
             time_incr++;
 

         check_marker(s->avctx, &s->gb, "before time_increment in video packed header");

         skip_bits(&s->gb, ctx->time_increment_bits);      /* time_increment */

         check_marker(s->avctx, &s->gb, "before vop_coding_type in video packed header");

 
         skip_bits(&s->gb, 2); /* vop coding type */

         // FIXME not rect stuff here

         if (ctx->shape != BIN_ONLY_SHAPE) {

             skip_bits(&s->gb, 3); /* intra dc vlc threshold */

             // FIXME don't just ignore everything
             if (s->pict_type == AV_PICTURE_TYPE_S &&

                 ctx->vol_sprite_usage == GMC_SPRITE) {

                 if (mpeg4_decode_sprite_trajectory(ctx, &s->gb) < 0)

                     return AVERROR_INVALIDDATA;

                 av_log(s->avctx, AV_LOG_ERROR, "untested\n");
             }
 

             // FIXME reduced res stuff here

             if (s->pict_type != AV_PICTURE_TYPE_I) {

                 int f_code = get_bits(&s->gb, 3);       /* fcode_for */

                 if (f_code == 0)
                     av_log(s->avctx, AV_LOG_ERROR,
                            "Error, video packet header damaged (f_code=0)\n");

             }

             if (s->pict_type == AV_PICTURE_TYPE_B) {

                 int b_code = get_bits(&s->gb, 3);

                 if (b_code == 0)
                     av_log(s->avctx, AV_LOG_ERROR,
                            "Error, video packet header damaged (b_code=0)\n");

             }
         }
     }

     if (ctx->new_pred)

         decode_new_pred(ctx, &s->gb);

 
     return 0;
 }
 

 static void reset_studio_dc_predictors(MpegEncContext *s)
 {
     /* Reset DC Predictors */
     s->last_dc[0] =
     s->last_dc[1] =
     s->last_dc[2] = 1 << (s->avctx->bits_per_raw_sample + s->dct_precision + s->intra_dc_precision - 1);
 }
 
 /**
  * Decode the next video packet.
  * @return <0 if something went wrong
  */
 int ff_mpeg4_decode_studio_slice_header(Mpeg4DecContext *ctx)
 {
     MpegEncContext *s = &ctx->m;
     GetBitContext *gb = &s->gb;
     unsigned vlc_len;
     uint16_t mb_num;
 
     if (get_bits_left(gb) >= 32 && get_bits_long(gb, 32) == SLICE_START_CODE) {
         vlc_len = av_log2(s->mb_width * s->mb_height) + 1;
         mb_num = get_bits(gb, vlc_len);
 
         if (mb_num >= s->mb_num)
             return AVERROR_INVALIDDATA;
 
         s->mb_x = mb_num % s->mb_width;
         s->mb_y = mb_num / s->mb_width;
 
         if (ctx->shape != BIN_ONLY_SHAPE)
             s->qscale = mpeg_get_qscale(s);
 
         if (get_bits1(gb)) {  /* slice_extension_flag */
             skip_bits1(gb);   /* intra_slice */
             skip_bits1(gb);   /* slice_VOP_id_enable */
             skip_bits(gb, 6); /* slice_VOP_id */
             while (get_bits1(gb)) /* extra_bit_slice */
                 skip_bits(gb, 8); /* extra_information_slice */
         }
 
         reset_studio_dc_predictors(s);
     }
     else {
         return AVERROR_INVALIDDATA;
     }
 
     return 0;
 }
 

 /**

  * Get the average motion vector for a GMC MB.

  * @param n either 0 for the x component or 1 for y

  * @return the average MV for a GMC MB

  */

 static inline int get_amv(Mpeg4DecContext *ctx, int n)

 {

     MpegEncContext *s = &ctx->m;

     int x, y, mb_v, sum, dx, dy, shift;

     int len     = 1 << (s->f_code + 4);
     const int a = s->sprite_warping_accuracy;

     if (s->workaround_bugs & FF_BUG_AMV)

         len >>= s->quarter_sample;
 

     if (s->real_sprite_warping_points == 1) {

         if (ctx->divx_version == 500 && ctx->divx_build == 413)

             sum = s->sprite_offset[0][n] / (1 << (a - s->quarter_sample));
         else

             sum = RSHIFT(s->sprite_offset[0][n] * (1 << s->quarter_sample), a);

     } else {
         dx    = s->sprite_delta[n][0];
         dy    = s->sprite_delta[n][1];

         shift = ctx->sprite_shift[0];

         if (n)
             dy -= 1 << (shift + a + 1);

         else

             dx -= 1 << (shift + a + 1);
         mb_v = s->sprite_offset[0][n] + dx * s->mb_x * 16 + dy * s->mb_y * 16;
 
         sum = 0;
         for (y = 0; y < 16; y++) {

             int v;
 

             v = mb_v + dy * y;
             // FIXME optimize
             for (x = 0; x < 16; x++) {
                 sum += v >> shift;
                 v   += dx;

             }
         }

         sum = RSHIFT(sum, a + 8 - s->quarter_sample);

     }
 

     if (sum < -len)
         sum = -len;
     else if (sum >= len)
         sum = len - 1;

 
     return sum;
 }
 
 /**

  * Decode the dc value.

  * @param n block index (0-3 are luma, 4-5 are chroma)
  * @param dir_ptr the prediction direction will be stored here
  * @return the quantized dc
  */

 static inline int mpeg4_decode_dc(MpegEncContext *s, int n, int *dir_ptr)

 {
     int level, code;
 
     if (n < 4)
         code = get_vlc2(&s->gb, dc_lum.table, DC_VLC_BITS, 1);
     else
         code = get_vlc2(&s->gb, dc_chrom.table, DC_VLC_BITS, 1);

 
     if (code < 0 || code > 9 /* && s->nbit < 9 */) {

         av_log(s->avctx, AV_LOG_ERROR, "illegal dc vlc\n");

         return AVERROR_INVALIDDATA;

     }

     if (code == 0) {
         level = 0;
     } else {

         if (IS_3IV1) {
             if (code == 1)
                 level = 2 * get_bits1(&s->gb) - 1;
             else {
                 if (get_bits1(&s->gb))
                     level = get_bits(&s->gb, code - 1) + (1 << (code - 1));

                 else

                     level = -get_bits(&s->gb, code - 1) - (1 << (code - 1));

             }

         } else {

             level = get_xbits(&s->gb, code);
         }
 

         if (code > 8) {
             if (get_bits1(&s->gb) == 0) { /* marker */

                 if (s->avctx->err_recognition & (AV_EF_BITSTREAM|AV_EF_COMPLIANT)) {

                     av_log(s->avctx, AV_LOG_ERROR, "dc marker bit missing\n");

                     return AVERROR_INVALIDDATA;

                 }
             }
         }
     }
 
     return ff_mpeg4_pred_dc(s, n, level, dir_ptr, 0);
 }
 
 /**

  * Decode first partition.

  * @return number of MBs decoded or <0 if an error occurred
  */

 static int mpeg4_decode_partition_a(Mpeg4DecContext *ctx)

 {

     MpegEncContext *s = &ctx->m;

     int mb_num = 0;

     static const int8_t quant_tab[4] = { -1, -2, 1, 2 };
 
     /* decode first partition */

     s->first_slice_line = 1;
     for (; s->mb_y < s->mb_height; s->mb_y++) {

         ff_init_block_index(s);

         for (; s->mb_x < s->mb_width; s->mb_x++) {
             const int xy = s->mb_x + s->mb_y * s->mb_stride;

             int cbpc;

             int dir = 0;

 
             mb_num++;
             ff_update_block_index(s);

             if (s->mb_x == s->resync_mb_x && s->mb_y == s->resync_mb_y + 1)
                 s->first_slice_line = 0;

             if (s->pict_type == AV_PICTURE_TYPE_I) {

                 int i;
 

                 do {
                     if (show_bits_long(&s->gb, 19) == DC_MARKER)
                         return mb_num - 1;

                     cbpc = get_vlc2(&s->gb, ff_h263_intra_MCBPC_vlc.table, INTRA_MCBPC_VLC_BITS, 2);

                     if (cbpc < 0) {
                         av_log(s->avctx, AV_LOG_ERROR,

                                "mcbpc corrupted at %d %d\n", s->mb_x, s->mb_y);

                         return AVERROR_INVALIDDATA;

                     }

                 } while (cbpc == 8);

                 s->cbp_table[xy]               = cbpc & 3;

                 s->current_picture.mb_type[xy] = MB_TYPE_INTRA;

                 s->mb_intra                    = 1;

                 if (cbpc & 4)

                     ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);
 

                 s->current_picture.qscale_table[xy] = s->qscale;
 
                 s->mbintra_table[xy] = 1;
                 for (i = 0; i < 6; i++) {

                     int dc_pred_dir;

                     int dc = mpeg4_decode_dc(s, i, &dc_pred_dir);
                     if (dc < 0) {
                         av_log(s->avctx, AV_LOG_ERROR,
                                "DC corrupted at %d %d\n", s->mb_x, s->mb_y);

                         return dc;

                     }

                     dir <<= 1;
                     if (dc_pred_dir)
                         dir |= 1;

                 }

                 s->pred_dir_table[xy] = dir;
             } else { /* P/S_TYPE */

                 int mx, my, pred_x, pred_y, bits;

                 int16_t *const mot_val = s->current_picture.motion_val[0][s->block_index[0]];
                 const int stride       = s->b8_stride * 2;

 
 try_again:

                 bits = show_bits(&s->gb, 17);
                 if (bits == MOTION_MARKER)
                     return mb_num - 1;
 

                 skip_bits1(&s->gb);

                 if (bits & 0x10000) {

                     /* skip mb */

                     if (s->pict_type == AV_PICTURE_TYPE_S &&

                         ctx->vol_sprite_usage == GMC_SPRITE) {

                         s->current_picture.mb_type[xy] = MB_TYPE_SKIP  |
                                                          MB_TYPE_16x16 |
                                                          MB_TYPE_GMC   |
                                                          MB_TYPE_L0;

                         mx = get_amv(ctx, 0);
                         my = get_amv(ctx, 1);

                     } else {
                         s->current_picture.mb_type[xy] = MB_TYPE_SKIP  |
                                                          MB_TYPE_16x16 |
                                                          MB_TYPE_L0;
                         mx = my = 0;

                     }

                     mot_val[0]          =
                     mot_val[2]          =
                     mot_val[0 + stride] =
                     mot_val[2 + stride] = mx;
                     mot_val[1]          =
                     mot_val[3]          =
                     mot_val[1 + stride] =
                     mot_val[3 + stride] = my;
 
                     if (s->mbintra_table[xy])

                         ff_clean_intra_table_entries(s);
                     continue;
                 }
 

                 cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);

                 if (cbpc < 0) {
                     av_log(s->avctx, AV_LOG_ERROR,

                            "mcbpc corrupted at %d %d\n", s->mb_x, s->mb_y);

                     return AVERROR_INVALIDDATA;

                 }

                 if (cbpc == 20)

                     goto try_again;
 

                 s->cbp_table[xy] = cbpc & (8 + 3);  // 8 is dquant

 
                 s->mb_intra = ((cbpc & 4) != 0);
 

                 if (s->mb_intra) {

                     s->current_picture.mb_type[xy] = MB_TYPE_INTRA;

                     s->mbintra_table[xy] = 1;
                     mot_val[0]          =
                     mot_val[2]          =
                     mot_val[0 + stride] =
                     mot_val[2 + stride] = 0;
                     mot_val[1]          =
                     mot_val[3]          =
                     mot_val[1 + stride] =
                     mot_val[3 + stride] = 0;
                 } else {
                     if (s->mbintra_table[xy])

                         ff_clean_intra_table_entries(s);
 

                     if (s->pict_type == AV_PICTURE_TYPE_S &&

                         ctx->vol_sprite_usage == GMC_SPRITE &&

                         (cbpc & 16) == 0)
                         s->mcsel = get_bits1(&s->gb);
                     else
                         s->mcsel = 0;

 
                     if ((cbpc & 16) == 0) {
                         /* 16x16 motion prediction */
 

                         ff_h263_pred_motion(s, 0, 0, &pred_x, &pred_y);

                         if (!s->mcsel) {

                             mx = ff_h263_decode_motion(s, pred_x, s->f_code);

                             if (mx >= 0xffff)

                                 return AVERROR_INVALIDDATA;

                             my = ff_h263_decode_motion(s, pred_y, s->f_code);

                             if (my >= 0xffff)

                                 return AVERROR_INVALIDDATA;

                             s->current_picture.mb_type[xy] = MB_TYPE_16x16 |
                                                              MB_TYPE_L0;

                         } else {

                             mx = get_amv(ctx, 0);
                             my = get_amv(ctx, 1);

                             s->current_picture.mb_type[xy] = MB_TYPE_16x16 |
                                                              MB_TYPE_GMC   |
                                                              MB_TYPE_L0;

                         }
 

                         mot_val[0]          =
                         mot_val[2]          =
                         mot_val[0 + stride] =
                         mot_val[2 + stride] = mx;
                         mot_val[1]          =
                         mot_val[3]          =
                         mot_val[1 + stride] =
                         mot_val[3 + stride] = my;

                     } else {
                         int i;

                         s->current_picture.mb_type[xy] = MB_TYPE_8x8 |
                                                          MB_TYPE_L0;
                         for (i = 0; i < 4; i++) {
                             int16_t *mot_val = ff_h263_pred_motion(s, i, 0, &pred_x, &pred_y);

                             mx = ff_h263_decode_motion(s, pred_x, s->f_code);

                             if (mx >= 0xffff)

                                 return AVERROR_INVALIDDATA;

                             my = ff_h263_decode_motion(s, pred_y, s->f_code);

                             if (my >= 0xffff)

                                 return AVERROR_INVALIDDATA;

                             mot_val[0] = mx;
                             mot_val[1] = my;
                         }
                     }
                 }
             }
         }

         s->mb_x = 0;

     }
 
     return mb_num;
 }
 
 /**
  * decode second partition.
  * @return <0 if an error occurred
  */

 static int mpeg4_decode_partition_b(MpegEncContext *s, int mb_count)
 {
     int mb_num = 0;

     static const int8_t quant_tab[4] = { -1, -2, 1, 2 };
 

     s->mb_x = s->resync_mb_x;
     s->first_slice_line = 1;
     for (s->mb_y = s->resync_mb_y; mb_num < mb_count; s->mb_y++) {

         ff_init_block_index(s);

         for (; mb_num < mb_count && s->mb_x < s->mb_width; s->mb_x++) {
             const int xy = s->mb_x + s->mb_y * s->mb_stride;

 
             mb_num++;
             ff_update_block_index(s);

             if (s->mb_x == s->resync_mb_x && s->mb_y == s->resync_mb_y + 1)
                 s->first_slice_line = 0;
 
             if (s->pict_type == AV_PICTURE_TYPE_I) {
                 int ac_pred = get_bits1(&s->gb);
                 int cbpy    = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
                 if (cbpy < 0) {
                     av_log(s->avctx, AV_LOG_ERROR,
                            "cbpy corrupted at %d %d\n", s->mb_x, s->mb_y);

                     return AVERROR_INVALIDDATA;

                 }
 

                 s->cbp_table[xy]               |= cbpy << 2;
                 s->current_picture.mb_type[xy] |= ac_pred * MB_TYPE_ACPRED;
             } else { /* P || S_TYPE */

                 if (IS_INTRA(s->current_picture.mb_type[xy])) {

                     int i;
                     int dir     = 0;

                     int ac_pred = get_bits1(&s->gb);

                     int cbpy    = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);

                     if (cbpy < 0) {
                         av_log(s->avctx, AV_LOG_ERROR,
                                "I cbpy corrupted at %d %d\n", s->mb_x, s->mb_y);

                         return AVERROR_INVALIDDATA;

                     }
 

                     if (s->cbp_table[xy] & 8)

                         ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);

                     s->current_picture.qscale_table[xy] = s->qscale;

                     for (i = 0; i < 6; i++) {

                         int dc_pred_dir;

                         int dc = mpeg4_decode_dc(s, i, &dc_pred_dir);
                         if (dc < 0) {
                             av_log(s->avctx, AV_LOG_ERROR,
                                    "DC corrupted at %d %d\n", s->mb_x, s->mb_y);

                             return dc;

                         }

                         dir <<= 1;
                         if (dc_pred_dir)
                             dir |= 1;

                     }

                     s->cbp_table[xy]               &= 3;  // remove dquant
                     s->cbp_table[xy]               |= cbpy << 2;
                     s->current_picture.mb_type[xy] |= ac_pred * MB_TYPE_ACPRED;
                     s->pred_dir_table[xy]           = dir;

                 } else if (IS_SKIP(s->current_picture.mb_type[xy])) {
                     s->current_picture.qscale_table[xy] = s->qscale;

                     s->cbp_table[xy]                    = 0;
                 } else {

                     int cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);

                     if (cbpy < 0) {
                         av_log(s->avctx, AV_LOG_ERROR,
                                "P cbpy corrupted at %d %d\n", s->mb_x, s->mb_y);

                         return AVERROR_INVALIDDATA;

                     }
 

                     if (s->cbp_table[xy] & 8)

                         ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);

                     s->current_picture.qscale_table[xy] = s->qscale;

                     s->cbp_table[xy] &= 3;  // remove dquant
                     s->cbp_table[xy] |= (cbpy ^ 0xf) << 2;

                 }
             }
         }

         if (mb_num >= mb_count)
             return 0;
         s->mb_x = 0;

     }
     return 0;
 }
 
 /**

  * Decode the first and second partition.

  * @return <0 if error (and sets error type in the error_status_table)
  */

 int ff_mpeg4_decode_partitions(Mpeg4DecContext *ctx)

 {

     MpegEncContext *s = &ctx->m;

     int mb_num;

     int ret;

     const int part_a_error = s->pict_type == AV_PICTURE_TYPE_I ? (ER_DC_ERROR | ER_MV_ERROR) : ER_MV_ERROR;
     const int part_a_end   = s->pict_type == AV_PICTURE_TYPE_I ? (ER_DC_END   | ER_MV_END)   : ER_MV_END;

     mb_num = mpeg4_decode_partition_a(ctx);

     if (mb_num <= 0) {

         ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                         s->mb_x, s->mb_y, part_a_error);

         return mb_num ? mb_num : AVERROR_INVALIDDATA;

     }
 

     if (s->resync_mb_x + s->resync_mb_y * s->mb_width + mb_num > s->mb_num) {

         av_log(s->avctx, AV_LOG_ERROR, "slice below monitor ...\n");

         ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                         s->mb_x, s->mb_y, part_a_error);

         return AVERROR_INVALIDDATA;

     }
 

     s->mb_num_left = mb_num;

     if (s->pict_type == AV_PICTURE_TYPE_I) {
         while (show_bits(&s->gb, 9) == 1)

             skip_bits(&s->gb, 9);

         if (get_bits_long(&s->gb, 19) != DC_MARKER) {
             av_log(s->avctx, AV_LOG_ERROR,
                    "marker missing after first I partition at %d %d\n",
                    s->mb_x, s->mb_y);

             return AVERROR_INVALIDDATA;

         }

     } else {
         while (show_bits(&s->gb, 10) == 1)

             skip_bits(&s->gb, 10);

         if (get_bits(&s->gb, 17) != MOTION_MARKER) {
             av_log(s->avctx, AV_LOG_ERROR,
                    "marker missing after first P partition at %d %d\n",
                    s->mb_x, s->mb_y);

             return AVERROR_INVALIDDATA;

         }
     }

     ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                     s->mb_x - 1, s->mb_y, part_a_end);

     ret = mpeg4_decode_partition_b(s, mb_num);
     if (ret < 0) {

         if (s->pict_type == AV_PICTURE_TYPE_P)
             ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                             s->mb_x, s->mb_y, ER_DC_ERROR);

         return ret;

     } else {
         if (s->pict_type == AV_PICTURE_TYPE_P)
             ff_er_add_slice(&s->er, s->resync_mb_x, s->resync_mb_y,
                             s->mb_x - 1, s->mb_y, ER_DC_END);

     }
 
     return 0;
 }
 
 /**

  * Decode a block.

  * @return <0 if an error occurred
  */

 static inline int mpeg4_decode_block(Mpeg4DecContext *ctx, int16_t *block,

                                      int n, int coded, int intra, int rvlc)

 {

     MpegEncContext *s = &ctx->m;

     int level, i, last, run, qmul, qadd;

     int av_uninit(dc_pred_dir);

     RLTable *rl;
     RL_VLC_ELEM *rl_vlc;
     const uint8_t *scan_table;
 
     // Note intra & rvlc should be optimized away if this is inlined
 
     if (intra) {

         if (ctx->use_intra_dc_vlc) {

             /* DC coef */
             if (s->partitioned_frame) {
                 level = s->dc_val[0][s->block_index[n]];
                 if (n < 4)
                     level = FASTDIV((level + (s->y_dc_scale >> 1)), s->y_dc_scale);
                 else
                     level = FASTDIV((level + (s->c_dc_scale >> 1)), s->c_dc_scale);
                 dc_pred_dir = (s->pred_dir_table[s->mb_x + s->mb_y * s->mb_stride] << n) & 32;
             } else {
                 level = mpeg4_decode_dc(s, n, &dc_pred_dir);
                 if (level < 0)

                     return level;

             }
             block[0] = level;
             i        = 0;
         } else {

             i = -1;
             ff_mpeg4_pred_dc(s, n, 0, &dc_pred_dir, 0);

         }
         if (!coded)
             goto not_coded;
 
         if (rvlc) {
             rl     = &ff_rvlc_rl_intra;
             rl_vlc = ff_rvlc_rl_intra.rl_vlc[0];
         } else {
             rl     = &ff_mpeg4_rl_intra;
             rl_vlc = ff_mpeg4_rl_intra.rl_vlc[0];
         }
         if (s->ac_pred) {
             if (dc_pred_dir == 0)
                 scan_table = s->intra_v_scantable.permutated;  /* left */
             else
                 scan_table = s->intra_h_scantable.permutated;  /* top */
         } else {

             scan_table = s->intra_scantable.permutated;

         }
         qmul = 1;
         qadd = 0;

     } else {
         i = -1;
         if (!coded) {
             s->block_last_index[n] = i;
             return 0;
         }

         if (rvlc)
             rl = &ff_rvlc_rl_inter;
         else
             rl = &ff_h263_rl_inter;

 
         scan_table = s->intra_scantable.permutated;
 

         if (s->mpeg_quant) {
             qmul = 1;
             qadd = 0;
             if (rvlc)

                 rl_vlc = ff_rvlc_rl_inter.rl_vlc[0];

             else

                 rl_vlc = ff_h263_rl_inter.rl_vlc[0];

         } else {

             qmul = s->qscale << 1;
             qadd = (s->qscale - 1) | 1;

             if (rvlc)

                 rl_vlc = ff_rvlc_rl_inter.rl_vlc[s->qscale];

             else

                 rl_vlc = ff_h263_rl_inter.rl_vlc[s->qscale];

         }
     }

     {
         OPEN_READER(re, &s->gb);
         for (;;) {
             UPDATE_CACHE(re, &s->gb);
             GET_RL_VLC(level, run, re, &s->gb, rl_vlc, TEX_VLC_BITS, 2, 0);
             if (level == 0) {
                 /* escape */
                 if (rvlc) {
                     if (SHOW_UBITS(re, &s->gb, 1) == 0) {
                         av_log(s->avctx, AV_LOG_ERROR,
                                "1. marker bit missing in rvlc esc\n");

                         return AVERROR_INVALIDDATA;

                     }
                     SKIP_CACHE(re, &s->gb, 1);

                     last = SHOW_UBITS(re, &s->gb, 1);
                     SKIP_CACHE(re, &s->gb, 1);
                     run = SHOW_UBITS(re, &s->gb, 6);
                     SKIP_COUNTER(re, &s->gb, 1 + 1 + 6);

                     UPDATE_CACHE(re, &s->gb);
 

                     if (SHOW_UBITS(re, &s->gb, 1) == 0) {
                         av_log(s->avctx, AV_LOG_ERROR,
                                "2. marker bit missing in rvlc esc\n");

                         return AVERROR_INVALIDDATA;

                     }
                     SKIP_CACHE(re, &s->gb, 1);

                     level = SHOW_UBITS(re, &s->gb, 11);
                     SKIP_CACHE(re, &s->gb, 11);

                     if (SHOW_UBITS(re, &s->gb, 5) != 0x10) {
                         av_log(s->avctx, AV_LOG_ERROR, "reverse esc missing\n");

                         return AVERROR_INVALIDDATA;

                     }

                     SKIP_CACHE(re, &s->gb, 5);

                     level = level * qmul + qadd;
                     level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                     SKIP_COUNTER(re, &s->gb, 1 + 11 + 5 + 1);

                     i += run + 1;
                     if (last)
                         i += 192;
                 } else {
                     int cache;
                     cache = GET_CACHE(re, &s->gb);
 
                     if (IS_3IV1)
                         cache ^= 0xC0000000;
 
                     if (cache & 0x80000000) {
                         if (cache & 0x40000000) {
                             /* third escape */
                             SKIP_CACHE(re, &s->gb, 2);
                             last = SHOW_UBITS(re, &s->gb, 1);
                             SKIP_CACHE(re, &s->gb, 1);
                             run = SHOW_UBITS(re, &s->gb, 6);
                             SKIP_COUNTER(re, &s->gb, 2 + 1 + 6);
                             UPDATE_CACHE(re, &s->gb);
 
                             if (IS_3IV1) {
                                 level = SHOW_SBITS(re, &s->gb, 12);
                                 LAST_SKIP_BITS(re, &s->gb, 12);
                             } else {
                                 if (SHOW_UBITS(re, &s->gb, 1) == 0) {
                                     av_log(s->avctx, AV_LOG_ERROR,
                                            "1. marker bit missing in 3. esc\n");

                                     if (!(s->avctx->err_recognition & AV_EF_IGNORE_ERR))

                                         return AVERROR_INVALIDDATA;

                                 }
                                 SKIP_CACHE(re, &s->gb, 1);

                                 level = SHOW_SBITS(re, &s->gb, 12);
                                 SKIP_CACHE(re, &s->gb, 12);

                                 if (SHOW_UBITS(re, &s->gb, 1) == 0) {
                                     av_log(s->avctx, AV_LOG_ERROR,
                                            "2. marker bit missing in 3. esc\n");

                                     if (!(s->avctx->err_recognition & AV_EF_IGNORE_ERR))

                                         return AVERROR_INVALIDDATA;

                                 }

                                 SKIP_COUNTER(re, &s->gb, 1 + 12 + 1);

                             }
 
 #if 0

                             if (s->error_recognition >= FF_ER_COMPLIANT) {
                                 const int abs_level= FFABS(level);
                                 if (abs_level<=MAX_LEVEL && run<=MAX_RUN) {
                                     const int run1= run - rl->max_run[last][abs_level] - 1;
                                     if (abs_level <= rl->max_level[last][run]) {
                                         av_log(s->avctx, AV_LOG_ERROR, "illegal 3. esc, vlc encoding possible\n");

                                         return AVERROR_INVALIDDATA;

                                     }
                                     if (s->error_recognition > FF_ER_COMPLIANT) {
                                         if (abs_level <= rl->max_level[last][run]*2) {
                                             av_log(s->avctx, AV_LOG_ERROR, "illegal 3. esc, esc 1 encoding possible\n");

                                             return AVERROR_INVALIDDATA;

                                         }
                                         if (run1 >= 0 && abs_level <= rl->max_level[last][run1]) {
                                             av_log(s->avctx, AV_LOG_ERROR, "illegal 3. esc, esc 2 encoding possible\n");

                                             return AVERROR_INVALIDDATA;

                                         }
                                     }

                                 }
                             }
 #endif

                             if (level > 0)
                                 level = level * qmul + qadd;
                             else
                                 level = level * qmul - qadd;
 
                             if ((unsigned)(level + 2048) > 4095) {

                                 if (s->avctx->err_recognition & (AV_EF_BITSTREAM|AV_EF_AGGRESSIVE)) {

                                     if (level > 2560 || level < -2560) {
                                         av_log(s->avctx, AV_LOG_ERROR,
                                                "|level| overflow in 3. esc, qp=%d\n",
                                                s->qscale);

                                         return AVERROR_INVALIDDATA;

                                     }
                                 }
                                 level = level < 0 ? -2048 : 2047;

                             }

 
                             i += run + 1;
                             if (last)
                                 i += 192;
                         } else {
                             /* second escape */
                             SKIP_BITS(re, &s->gb, 2);
                             GET_RL_VLC(level, run, re, &s->gb, rl_vlc, TEX_VLC_BITS, 2, 1);
                             i    += run + rl->max_run[run >> 7][level / qmul] + 1;  // FIXME opt indexing
                             level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                             LAST_SKIP_BITS(re, &s->gb, 1);

                         }

                     } else {
                         /* first escape */
                         SKIP_BITS(re, &s->gb, 1);
                         GET_RL_VLC(level, run, re, &s->gb, rl_vlc, TEX_VLC_BITS, 2, 1);
                         i    += run;
                         level = level + rl->max_level[run >> 7][(run - 1) & 63] * qmul;  // FIXME opt indexing
                         level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                         LAST_SKIP_BITS(re, &s->gb, 1);

                     }
                 }
             } else {

                 i    += run;

                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                 LAST_SKIP_BITS(re, &s->gb, 1);
             }

             ff_tlog(s->avctx, "dct[%d][%d] = %- 4d end?:%d\n", scan_table[i&63]&7, scan_table[i&63] >> 3, level, i>62);

             if (i > 62) {
                 i -= 192;
                 if (i & (~63)) {
                     av_log(s->avctx, AV_LOG_ERROR,
                            "ac-tex damaged at %d %d\n", s->mb_x, s->mb_y);

                     return AVERROR_INVALIDDATA;

                 }
 
                 block[scan_table[i]] = level;
                 break;

             }
 
             block[scan_table[i]] = level;
         }

         CLOSE_READER(re, &s->gb);

     }

 
 not_coded:

     if (intra) {

         if (!ctx->use_intra_dc_vlc) {

             block[0] = ff_mpeg4_pred_dc(s, n, block[0], &dc_pred_dir, 0);
 

             i -= i >> 31;  // if (i == -1) i = 0;

         }
 

         ff_mpeg4_pred_ac(s, block, n, dc_pred_dir);

         if (s->ac_pred)
             i = 63;  // FIXME not optimal

     }
     s->block_last_index[n] = i;
     return 0;
 }
 
 /**
  * decode partition C of one MB.
  * @return <0 if an error occurred
  */

 static int mpeg4_decode_partitioned_mb(MpegEncContext *s, int16_t block[6][64])

 {

     Mpeg4DecContext *ctx = s->avctx->priv_data;

     int cbp, mb_type;

     const int xy = s->mb_x + s->mb_y * s->mb_stride;

     av_assert2(s == (void*)ctx);
 

     mb_type = s->current_picture.mb_type[xy];

     cbp     = s->cbp_table[xy];

     ctx->use_intra_dc_vlc = s->qscale < ctx->intra_dc_threshold;

     if (s->current_picture.qscale_table[xy] != s->qscale)

         ff_set_qscale(s, s->current_picture.qscale_table[xy]);

     if (s->pict_type == AV_PICTURE_TYPE_P ||
         s->pict_type == AV_PICTURE_TYPE_S) {

         int i;

         for (i = 0; i < 4; i++) {

             s->mv[0][i][0] = s->current_picture.motion_val[0][s->block_index[i]][0];
             s->mv[0][i][1] = s->current_picture.motion_val[0][s->block_index[i]][1];

         }
         s->mb_intra = IS_INTRA(mb_type);
 
         if (IS_SKIP(mb_type)) {
             /* skip mb */

             for (i = 0; i < 6; i++)

                 s->block_last_index[i] = -1;

             s->mv_dir  = MV_DIR_FORWARD;

             s->mv_type = MV_TYPE_16X16;

             if (s->pict_type == AV_PICTURE_TYPE_S

                 && ctx->vol_sprite_usage == GMC_SPRITE) {

                 s->mcsel      = 1;

                 s->mb_skipped = 0;

             } else {
                 s->mcsel      = 0;

                 s->mb_skipped = 1;
             }

         } else if (s->mb_intra) {

             s->ac_pred = IS_ACPRED(s->current_picture.mb_type[xy]);

         } else if (!s->mb_intra) {
             // s->mcsel = 0;  // FIXME do we need to init that?

 
             s->mv_dir = MV_DIR_FORWARD;
             if (IS_8X8(mb_type)) {
                 s->mv_type = MV_TYPE_8X8;
             } else {
                 s->mv_type = MV_TYPE_16X16;
             }
         }
     } else { /* I-Frame */
         s->mb_intra = 1;

         s->ac_pred  = IS_ACPRED(s->current_picture.mb_type[xy]);

     }
 
     if (!IS_SKIP(mb_type)) {
         int i;

         s->bdsp.clear_blocks(s->block[0]);

         /* decode each block */
         for (i = 0; i < 6; i++) {

             if (mpeg4_decode_block(ctx, block[i], i, cbp & 32, s->mb_intra, ctx->rvlc) < 0) {

                 av_log(s->avctx, AV_LOG_ERROR,
                        "texture corrupted at %d %d %d\n",
                        s->mb_x, s->mb_y, s->mb_intra);

                 return AVERROR_INVALIDDATA;

             }

             cbp += cbp;

         }
     }
 
     /* per-MB end of slice check */

     if (--s->mb_num_left <= 0) {

         if (mpeg4_is_resync(ctx))

             return SLICE_END;
         else
             return SLICE_NOEND;

     } else {

         if (mpeg4_is_resync(ctx)) {

             const int delta = s->mb_x + 1 == s->mb_width ? 2 : 1;
             if (s->cbp_table[xy + delta])

                 return SLICE_END;
         }
         return SLICE_OK;
     }
 }
 

 static int mpeg4_decode_mb(MpegEncContext *s, int16_t block[6][64])

 {

     Mpeg4DecContext *ctx = s->avctx->priv_data;

     int cbpc, cbpy, i, cbp, pred_x, pred_y, mx, my, dquant;
     int16_t *mot_val;

     static const int8_t quant_tab[4] = { -1, -2, 1, 2 };

     const int xy = s->mb_x + s->mb_y * s->mb_stride;

     av_assert2(s ==  (void*)ctx);

     av_assert2(s->h263_pred);

     if (s->pict_type == AV_PICTURE_TYPE_P ||
         s->pict_type == AV_PICTURE_TYPE_S) {
         do {

             if (get_bits1(&s->gb)) {
                 /* skip mb */
                 s->mb_intra = 0;

                 for (i = 0; i < 6; i++)

                     s->block_last_index[i] = -1;

                 s->mv_dir  = MV_DIR_FORWARD;

                 s->mv_type = MV_TYPE_16X16;

                 if (s->pict_type == AV_PICTURE_TYPE_S &&

                     ctx->vol_sprite_usage == GMC_SPRITE) {

                     s->current_picture.mb_type[xy] = MB_TYPE_SKIP  |
                                                      MB_TYPE_GMC   |
                                                      MB_TYPE_16x16 |
                                                      MB_TYPE_L0;
                     s->mcsel       = 1;

                     s->mv[0][0][0] = get_amv(ctx, 0);
                     s->mv[0][0][1] = get_amv(ctx, 1);

                     s->mb_skipped  = 0;
                 } else {
                     s->current_picture.mb_type[xy] = MB_TYPE_SKIP  |
                                                      MB_TYPE_16x16 |
                                                      MB_TYPE_L0;
                     s->mcsel       = 0;

                     s->mv[0][0][0] = 0;
                     s->mv[0][0][1] = 0;

                     s->mb_skipped  = 1;

                 }
                 goto end;
             }

             cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);

             if (cbpc < 0) {
                 av_log(s->avctx, AV_LOG_ERROR,

                        "mcbpc damaged at %d %d\n", s->mb_x, s->mb_y);

                 return AVERROR_INVALIDDATA;

             }

         } while (cbpc == 20);

         s->bdsp.clear_blocks(s->block[0]);

         dquant      = cbpc & 8;

         s->mb_intra = ((cbpc & 4) != 0);

         if (s->mb_intra)
             goto intra;

         if (s->pict_type == AV_PICTURE_TYPE_S &&

             ctx->vol_sprite_usage == GMC_SPRITE && (cbpc & 16) == 0)

             s->mcsel = get_bits1(&s->gb);
         else
             s->mcsel = 0;

         cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1) ^ 0x0F;

         if (cbpy < 0) {
             av_log(s->avctx, AV_LOG_ERROR,
                    "P cbpy damaged at %d %d\n", s->mb_x, s->mb_y);
             return AVERROR_INVALIDDATA;
         }

 
         cbp = (cbpc & 3) | (cbpy << 2);

         if (dquant)

             ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);

         if ((!s->progressive_sequence) &&
             (cbp || (s->workaround_bugs & FF_BUG_XVID_ILACE)))
             s->interlaced_dct = get_bits1(&s->gb);

 
         s->mv_dir = MV_DIR_FORWARD;
         if ((cbpc & 16) == 0) {

             if (s->mcsel) {
                 s->current_picture.mb_type[xy] = MB_TYPE_GMC   |
                                                  MB_TYPE_16x16 |
                                                  MB_TYPE_L0;

                 /* 16x16 global motion prediction */

                 s->mv_type     = MV_TYPE_16X16;

                 mx             = get_amv(ctx, 0);
                 my             = get_amv(ctx, 1);

                 s->mv[0][0][0] = mx;
                 s->mv[0][0][1] = my;

             } else if ((!s->progressive_sequence) && get_bits1(&s->gb)) {
                 s->current_picture.mb_type[xy] = MB_TYPE_16x8 |
                                                  MB_TYPE_L0   |
                                                  MB_TYPE_INTERLACED;

                 /* 16x8 field motion prediction */

                 s->mv_type = MV_TYPE_FIELD;

                 s->field_select[0][0] = get_bits1(&s->gb);
                 s->field_select[0][1] = get_bits1(&s->gb);

                 ff_h263_pred_motion(s, 0, 0, &pred_x, &pred_y);

                 for (i = 0; i < 2; i++) {

                     mx = ff_h263_decode_motion(s, pred_x, s->f_code);

                     if (mx >= 0xffff)

                         return AVERROR_INVALIDDATA;

                     my = ff_h263_decode_motion(s, pred_y / 2, s->f_code);

                     if (my >= 0xffff)

                         return AVERROR_INVALIDDATA;

 
                     s->mv[0][i][0] = mx;
                     s->mv[0][i][1] = my;
                 }

             } else {

                 s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;

                 /* 16x16 motion prediction */
                 s->mv_type = MV_TYPE_16X16;

                 ff_h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
                 mx = ff_h263_decode_motion(s, pred_x, s->f_code);

 
                 if (mx >= 0xffff)

                     return AVERROR_INVALIDDATA;

                 my = ff_h263_decode_motion(s, pred_y, s->f_code);

 
                 if (my >= 0xffff)

                     return AVERROR_INVALIDDATA;

                 s->mv[0][0][0] = mx;
                 s->mv[0][0][1] = my;
             }
         } else {

             s->current_picture.mb_type[xy] = MB_TYPE_8x8 | MB_TYPE_L0;

             s->mv_type                     = MV_TYPE_8X8;
             for (i = 0; i < 4; i++) {

                 mot_val = ff_h263_pred_motion(s, i, 0, &pred_x, &pred_y);

                 mx      = ff_h263_decode_motion(s, pred_x, s->f_code);

                 if (mx >= 0xffff)

                     return AVERROR_INVALIDDATA;

                 my = ff_h263_decode_motion(s, pred_y, s->f_code);

                 if (my >= 0xffff)

                     return AVERROR_INVALIDDATA;

                 s->mv[0][i][0] = mx;
                 s->mv[0][i][1] = my;

                 mot_val[0]     = mx;
                 mot_val[1]     = my;

             }
         }

     } else if (s->pict_type == AV_PICTURE_TYPE_B) {
         int modb1;   // first bit of modb
         int modb2;   // second bit of modb

         int mb_type;
 

         s->mb_intra = 0;  // B-frames never contain intra blocks
         s->mcsel    = 0;  //      ...               true gmc blocks

         if (s->mb_x == 0) {
             for (i = 0; i < 2; i++) {
                 s->last_mv[i][0][0] =
                 s->last_mv[i][0][1] =
                 s->last_mv[i][1][0] =
                 s->last_mv[i][1][1] = 0;

             }

             ff_thread_await_progress(&s->next_picture_ptr->tf, s->mb_y, 0);

         }
 

         /* if we skipped it in the future P-frame than skip it now too */

         s->mb_skipped = s->next_picture.mbskip_table[s->mb_y * s->mb_stride + s->mb_x];  // Note, skiptab=0 if last was GMC

         if (s->mb_skipped) {
             /* skip mb */
             for (i = 0; i < 6; i++)

                 s->block_last_index[i] = -1;
 

             s->mv_dir      = MV_DIR_FORWARD;
             s->mv_type     = MV_TYPE_16X16;
             s->mv[0][0][0] =
             s->mv[0][0][1] =
             s->mv[1][0][0] =

             s->mv[1][0][1] = 0;

             s->current_picture.mb_type[xy] = MB_TYPE_SKIP  |
                                              MB_TYPE_16x16 |
                                              MB_TYPE_L0;

             goto end;
         }
 

         modb1 = get_bits1(&s->gb);
         if (modb1) {
             // like MB_TYPE_B_DIRECT but no vectors coded
             mb_type = MB_TYPE_DIRECT2 | MB_TYPE_SKIP | MB_TYPE_L0L1;
             cbp     = 0;
         } else {
             modb2   = get_bits1(&s->gb);
             mb_type = get_vlc2(&s->gb, mb_type_b_vlc.table, MB_TYPE_B_VLC_BITS, 1);
             if (mb_type < 0) {

                 av_log(s->avctx, AV_LOG_ERROR, "illegal MB_type\n");

                 return AVERROR_INVALIDDATA;

             }

             mb_type = mb_type_b_map[mb_type];
             if (modb2) {
                 cbp = 0;
             } else {

                 s->bdsp.clear_blocks(s->block[0]);

                 cbp = get_bits(&s->gb, 6);

             }
 
             if ((!IS_DIRECT(mb_type)) && cbp) {

                 if (get_bits1(&s->gb))
                     ff_set_qscale(s, s->qscale + get_bits1(&s->gb) * 4 - 2);

             }
 

             if (!s->progressive_sequence) {
                 if (cbp)
                     s->interlaced_dct = get_bits1(&s->gb);

                 if (!IS_DIRECT(mb_type) && get_bits1(&s->gb)) {

                     mb_type |= MB_TYPE_16x8 | MB_TYPE_INTERLACED;
                     mb_type &= ~MB_TYPE_16x16;
 

                     if (USES_LIST(mb_type, 0)) {
                         s->field_select[0][0] = get_bits1(&s->gb);
                         s->field_select[0][1] = get_bits1(&s->gb);

                     }

                     if (USES_LIST(mb_type, 1)) {
                         s->field_select[1][0] = get_bits1(&s->gb);
                         s->field_select[1][1] = get_bits1(&s->gb);

                     }
                 }
             }
 
             s->mv_dir = 0;

             if ((mb_type & (MB_TYPE_DIRECT2 | MB_TYPE_INTERLACED)) == 0) {
                 s->mv_type = MV_TYPE_16X16;

                 if (USES_LIST(mb_type, 0)) {

                     s->mv_dir = MV_DIR_FORWARD;
 

                     mx = ff_h263_decode_motion(s, s->last_mv[0][0][0], s->f_code);
                     my = ff_h263_decode_motion(s, s->last_mv[0][0][1], s->f_code);

                     s->last_mv[0][1][0] =
                     s->last_mv[0][0][0] =
                     s->mv[0][0][0]      = mx;
                     s->last_mv[0][1][1] =
                     s->last_mv[0][0][1] =
                     s->mv[0][0][1]      = my;

                 }
 

                 if (USES_LIST(mb_type, 1)) {

                     s->mv_dir |= MV_DIR_BACKWARD;
 

                     mx = ff_h263_decode_motion(s, s->last_mv[1][0][0], s->b_code);
                     my = ff_h263_decode_motion(s, s->last_mv[1][0][1], s->b_code);

                     s->last_mv[1][1][0] =
                     s->last_mv[1][0][0] =
                     s->mv[1][0][0]      = mx;
                     s->last_mv[1][1][1] =
                     s->last_mv[1][0][1] =
                     s->mv[1][0][1]      = my;

                 }

             } else if (!IS_DIRECT(mb_type)) {
                 s->mv_type = MV_TYPE_FIELD;

                 if (USES_LIST(mb_type, 0)) {

                     s->mv_dir = MV_DIR_FORWARD;
 

                     for (i = 0; i < 2; i++) {
                         mx = ff_h263_decode_motion(s, s->last_mv[0][i][0], s->f_code);
                         my = ff_h263_decode_motion(s, s->last_mv[0][i][1] / 2, s->f_code);
                         s->last_mv[0][i][0] =
                         s->mv[0][i][0]      = mx;
                         s->last_mv[0][i][1] = (s->mv[0][i][1] = my) * 2;

                     }
                 }
 

                 if (USES_LIST(mb_type, 1)) {

                     s->mv_dir |= MV_DIR_BACKWARD;
 

                     for (i = 0; i < 2; i++) {
                         mx = ff_h263_decode_motion(s, s->last_mv[1][i][0], s->b_code);
                         my = ff_h263_decode_motion(s, s->last_mv[1][i][1] / 2, s->b_code);
                         s->last_mv[1][i][0] =
                         s->mv[1][i][0]      = mx;
                         s->last_mv[1][i][1] = (s->mv[1][i][1] = my) * 2;

                     }
                 }
             }
         }
 

         if (IS_DIRECT(mb_type)) {
             if (IS_SKIP(mb_type)) {
                 mx =
                 my = 0;
             } else {

                 mx = ff_h263_decode_motion(s, 0, 1);
                 my = ff_h263_decode_motion(s, 0, 1);

             }
 
             s->mv_dir = MV_DIR_FORWARD | MV_DIR_BACKWARD | MV_DIRECT;

             mb_type  |= ff_mpeg4_set_direct_mv(s, mx, my);

         }

         s->current_picture.mb_type[xy] = mb_type;

     } else { /* I-Frame */

         do {

             cbpc = get_vlc2(&s->gb, ff_h263_intra_MCBPC_vlc.table, INTRA_MCBPC_VLC_BITS, 2);

             if (cbpc < 0) {
                 av_log(s->avctx, AV_LOG_ERROR,
                        "I cbpc damaged at %d %d\n", s->mb_x, s->mb_y);

                 return AVERROR_INVALIDDATA;

             }

         } while (cbpc == 8);

 
         dquant = cbpc & 4;
         s->mb_intra = 1;

 intra:
         s->ac_pred = get_bits1(&s->gb);

         if (s->ac_pred)

             s->current_picture.mb_type[xy] = MB_TYPE_INTRA | MB_TYPE_ACPRED;

         else

             s->current_picture.mb_type[xy] = MB_TYPE_INTRA;

         cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);

         if (cbpy < 0) {
             av_log(s->avctx, AV_LOG_ERROR,
                    "I cbpy damaged at %d %d\n", s->mb_x, s->mb_y);

             return AVERROR_INVALIDDATA;

         }
         cbp = (cbpc & 3) | (cbpy << 2);
 

         ctx->use_intra_dc_vlc = s->qscale < ctx->intra_dc_threshold;

         if (dquant)

             ff_set_qscale(s, s->qscale + quant_tab[get_bits(&s->gb, 2)]);
 

         if (!s->progressive_sequence)
             s->interlaced_dct = get_bits1(&s->gb);

         s->bdsp.clear_blocks(s->block[0]);

         /* decode each block */
         for (i = 0; i < 6; i++) {

             if (mpeg4_decode_block(ctx, block[i], i, cbp & 32, 1, 0) < 0)

                 return AVERROR_INVALIDDATA;

             cbp += cbp;

         }
         goto end;
     }
 
     /* decode each block */
     for (i = 0; i < 6; i++) {

         if (mpeg4_decode_block(ctx, block[i], i, cbp & 32, 0, 0) < 0)

             return AVERROR_INVALIDDATA;

         cbp += cbp;

     }
 

 end:
     /* per-MB end of slice check */
     if (s->codec_id == AV_CODEC_ID_MPEG4) {

         int next = mpeg4_is_resync(ctx);

         if (next) {

             if        (s->mb_x + s->mb_y*s->mb_width + 1 >  next && (s->avctx->err_recognition & AV_EF_AGGRESSIVE)) {

                 return AVERROR_INVALIDDATA;

             } else if (s->mb_x + s->mb_y*s->mb_width + 1 >= next)
                 return SLICE_END;

             if (s->pict_type == AV_PICTURE_TYPE_B) {

                 const int delta= s->mb_x + 1 == s->mb_width ? 2 : 1;

                 ff_thread_await_progress(&s->next_picture_ptr->tf,

                                          (s->mb_x + delta >= s->mb_width)
                                          ? FFMIN(s->mb_y + 1, s->mb_height - 1)
                                          : s->mb_y, 0);

                 if (s->next_picture.mbskip_table[xy + delta])

                     return SLICE_OK;
             }
 
             return SLICE_END;

         }
     }
 
     return SLICE_OK;
 }
 

 /* As per spec, studio start code search isn't the same as the old type of start code */
 static void next_start_code_studio(GetBitContext *gb)
 {
     align_get_bits(gb);
 
     while (get_bits_left(gb) >= 24 && show_bits_long(gb, 24) != 0x1) {
         get_bits(gb, 8);
     }
 }
 
 /* additional_code, vlc index */
 static const uint8_t ac_state_tab[22][2] =
 {
     {0, 0},
     {0, 1},
     {1, 1},
     {2, 1},
     {3, 1},
     {4, 1},
     {5, 1},
     {1, 2},
     {2, 2},
     {3, 2},
     {4, 2},
     {5, 2},
     {6, 2},
     {1, 3},
     {2, 4},
     {3, 5},
     {4, 6},
     {5, 7},
     {6, 8},
     {7, 9},
     {8, 10},
     {0, 11}
 };
 
 static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n)
 {
     Mpeg4DecContext *ctx = s->avctx->priv_data;
 
     int cc, dct_dc_size, dct_diff, code, j, idx = 1, group = 0, run = 0,
         additional_code_len, sign, mismatch;
     VLC *cur_vlc = &ctx->studio_intra_tab[0];
     uint8_t *const scantable = s->intra_scantable.permutated;
     const uint16_t *quant_matrix;
     uint32_t flc;
     const int min = -1 *  (1 << (s->avctx->bits_per_raw_sample + 6));
     const int max =      ((1 << (s->avctx->bits_per_raw_sample + 6)) - 1);
 
     mismatch = 1;
 
     memset(block, 0, 64 * sizeof(int32_t));
 
     if (n < 4) {
         cc = 0;
         dct_dc_size = get_vlc2(&s->gb, ctx->studio_luma_dc.table, STUDIO_INTRA_BITS, 2);
         quant_matrix = s->intra_matrix;
     } else {
         cc = (n & 1) + 1;
         if (ctx->rgb)
             dct_dc_size = get_vlc2(&s->gb, ctx->studio_luma_dc.table, STUDIO_INTRA_BITS, 2);
         else
             dct_dc_size = get_vlc2(&s->gb, ctx->studio_chroma_dc.table, STUDIO_INTRA_BITS, 2);
         quant_matrix = s->chroma_intra_matrix;
     }
 
     if (dct_dc_size < 0) {
         av_log(s->avctx, AV_LOG_ERROR, "illegal dct_dc_size vlc\n");
         return AVERROR_INVALIDDATA;
     } else if (dct_dc_size == 0) {
         dct_diff = 0;
     } else {
         dct_diff = get_xbits(&s->gb, dct_dc_size);
 
         if (dct_dc_size > 8) {
             if(!check_marker(s->avctx, &s->gb, "dct_dc_size > 8"))
                 return AVERROR_INVALIDDATA;
         }
 
     }
 
     s->last_dc[cc] += dct_diff;
 
     if (s->mpeg_quant)
         block[0] = s->last_dc[cc] * (8 >> s->intra_dc_precision);
     else
         block[0] = s->last_dc[cc] * (8 >> s->intra_dc_precision) * (8 >> s->dct_precision);
     /* TODO: support mpeg_quant for AC coefficients */
 
     block[0] = av_clip(block[0], min, max);
     mismatch ^= block[0];
 
     /* AC Coefficients */
     while (1) {
         group = get_vlc2(&s->gb, cur_vlc->table, STUDIO_INTRA_BITS, 2);
 
         if (group < 0) {
             av_log(s->avctx, AV_LOG_ERROR, "illegal ac coefficient group vlc\n");
             return AVERROR_INVALIDDATA;
         }
 
         additional_code_len = ac_state_tab[group][0];
         cur_vlc = &ctx->studio_intra_tab[ac_state_tab[group][1]];
 
         if (group == 0) {
             /* End of Block */
             break;
         } else if (group >= 1 && group <= 6) {
             /* Zero run length (Table B.47) */
             run = 1 << additional_code_len;
             if (additional_code_len)
                 run += get_bits(&s->gb, additional_code_len);
             idx += run;
             continue;
         } else if (group >= 7 && group <= 12) {
             /* Zero run length and +/-1 level (Table B.48) */
             code = get_bits(&s->gb, additional_code_len);
             sign = code & 1;
             code >>= 1;
             run = (1 << (additional_code_len - 1)) + code;
             idx += run;
             j = scantable[idx++];
             block[j] = sign ? 1 : -1;
         } else if (group >= 13 && group <= 20) {
             /* Level value (Table B.49) */
             j = scantable[idx++];
             block[j] = get_xbits(&s->gb, additional_code_len);
         } else if (group == 21) {
             /* Escape */
             j = scantable[idx++];
             additional_code_len = s->avctx->bits_per_raw_sample + s->dct_precision + 4;
             flc = get_bits(&s->gb, additional_code_len);
             if (flc >> (additional_code_len-1))
                 block[j] = -1 * (( flc ^ ((1 << additional_code_len) -1)) + 1);
             else
                 block[j] = flc;
         }
         block[j] = ((8 * 2 * block[j] * quant_matrix[j] * s->qscale) >> s->dct_precision) / 32;
         block[j] = av_clip(block[j], min, max);
         mismatch ^= block[j];
     }
 
     block[63] ^= mismatch & 1;
 
     return 0;
 }
 
 static int mpeg4_decode_studio_mb(MpegEncContext *s, int16_t block_[12][64])
 {
     int i;
 
     /* StudioMacroblock */
     /* Assumes I-VOP */
     s->mb_intra = 1;
     if (get_bits1(&s->gb)) { /* compression_mode */
         /* DCT */
         /* macroblock_type, 1 or 2-bit VLC */
         if (!get_bits1(&s->gb)) {
             skip_bits1(&s->gb);
             s->qscale = mpeg_get_qscale(s);
         }
 
         for (i = 0; i < mpeg4_block_count[s->chroma_format]; i++) {
             if (mpeg4_decode_studio_block(s, (*s->block32)[i], i) < 0)
                 return AVERROR_INVALIDDATA;
         }
     } else {
         /* DPCM */
         check_marker(s->avctx, &s->gb, "DPCM block start");
         avpriv_request_sample(s->avctx, "DPCM encoded block");
         next_start_code_studio(&s->gb);
         return SLICE_ERROR;
     }
 
     if (get_bits_left(&s->gb) >= 24 && show_bits(&s->gb, 23) == 0) {
         next_start_code_studio(&s->gb);
         return SLICE_END;
     }
 
     return SLICE_OK;
 }
 

 static int mpeg4_decode_gop_header(MpegEncContext *s, GetBitContext *gb)
 {

     int hours, minutes, seconds;
 

     if (!show_bits(gb, 23)) {

         av_log(s->avctx, AV_LOG_WARNING, "GOP header invalid\n");

         return AVERROR_INVALIDDATA;

     }
 

     hours   = get_bits(gb, 5);
     minutes = get_bits(gb, 6);

     check_marker(s->avctx, gb, "in gop_header");

     seconds = get_bits(gb, 6);

     s->time_base = seconds + 60*(minutes + 60*hours);

 
     skip_bits1(gb);
     skip_bits1(gb);
 
     return 0;
 }
 

 static int mpeg4_decode_profile_level(MpegEncContext *s, GetBitContext *gb)
 {

     s->avctx->profile = get_bits(gb, 4);
     s->avctx->level   = get_bits(gb, 4);

     // for Simple profile, level 0
     if (s->avctx->profile == 0 && s->avctx->level == 8) {
         s->avctx->level = 0;
     }

     return 0;

 }
 

 static int mpeg4_decode_visual_object(MpegEncContext *s, GetBitContext *gb)
 {
     int visual_object_type;
     int is_visual_object_identifier = get_bits1(gb);
 
     if (is_visual_object_identifier) {
         skip_bits(gb, 4+3);
     }
     visual_object_type = get_bits(gb, 4);
 
     if (visual_object_type == VOT_VIDEO_ID ||
         visual_object_type == VOT_STILL_TEXTURE_ID) {
         int video_signal_type = get_bits1(gb);
         if (video_signal_type) {

             int video_range, color_description;
             skip_bits(gb, 3); // video_format
             video_range = get_bits1(gb);
             color_description = get_bits1(gb);

 
             s->avctx->color_range = video_range ? AVCOL_RANGE_JPEG : AVCOL_RANGE_MPEG;
 
             if (color_description) {
                 s->avctx->color_primaries = get_bits(gb, 8);
                 s->avctx->color_trc       = get_bits(gb, 8);
                 s->avctx->colorspace      = get_bits(gb, 8);
             }
         }
     }
 
     return 0;
 }
 

 static void mpeg4_load_default_matrices(MpegEncContext *s)
 {
     int i, v;
 
     /* load default matrices */
     for (i = 0; i < 64; i++) {
         int j = s->idsp.idct_permutation[i];
         v = ff_mpeg4_default_intra_matrix[i];
         s->intra_matrix[j]        = v;
         s->chroma_intra_matrix[j] = v;
 
         v = ff_mpeg4_default_non_intra_matrix[i];
         s->inter_matrix[j]        = v;
         s->chroma_inter_matrix[j] = v;
     }
 }
 

 static int decode_vol_header(Mpeg4DecContext *ctx, GetBitContext *gb)

 {

     MpegEncContext *s = &ctx->m;

     int width, height, vo_ver_id;
 
     /* vol header */

     skip_bits(gb, 1);                   /* random access */
     s->vo_type = get_bits(gb, 8);
     if (get_bits1(gb) != 0) {           /* is_ol_id */
         vo_ver_id = get_bits(gb, 4);    /* vo_ver_id */
         skip_bits(gb, 3);               /* vo_priority */

     } else {
         vo_ver_id = 1;
     }

     s->aspect_ratio_info = get_bits(gb, 4);
     if (s->aspect_ratio_info == FF_ASPECT_EXTENDED) {
         s->avctx->sample_aspect_ratio.num = get_bits(gb, 8);  // par_width
         s->avctx->sample_aspect_ratio.den = get_bits(gb, 8);  // par_height
     } else {
         s->avctx->sample_aspect_ratio = ff_h263_pixel_aspect[s->aspect_ratio_info];

     }
 

     if ((ctx->vol_control_parameters = get_bits1(gb))) { /* vol control parameter */

         int chroma_format = get_bits(gb, 2);
         if (chroma_format != CHROMA_420)

             av_log(s->avctx, AV_LOG_ERROR, "illegal chroma format\n");

 
         s->low_delay = get_bits1(gb);
         if (get_bits1(gb)) {    /* vbv parameters */

             get_bits(gb, 15);   /* first_half_bitrate */

             check_marker(s->avctx, gb, "after first_half_bitrate");

             get_bits(gb, 15);   /* latter_half_bitrate */

             check_marker(s->avctx, gb, "after latter_half_bitrate");

             get_bits(gb, 15);   /* first_half_vbv_buffer_size */

             check_marker(s->avctx, gb, "after first_half_vbv_buffer_size");

             get_bits(gb, 3);    /* latter_half_vbv_buffer_size */
             get_bits(gb, 11);   /* first_half_vbv_occupancy */

             check_marker(s->avctx, gb, "after first_half_vbv_occupancy");

             get_bits(gb, 15);   /* latter_half_vbv_occupancy */

             check_marker(s->avctx, gb, "after latter_half_vbv_occupancy");

         }

     } else {
         /* is setting low delay flag only once the smartest thing to do?

          * low delay detection will not be overridden. */

         if (s->picture_number == 0) {
             switch(s->vo_type) {
             case SIMPLE_VO_TYPE:
             case ADV_SIMPLE_VO_TYPE:
                 s->low_delay = 1;
                 break;
             default:
                 s->low_delay = 0;
             }
         }

     }
 

     ctx->shape = get_bits(gb, 2); /* vol shape */
     if (ctx->shape != RECT_SHAPE)

         av_log(s->avctx, AV_LOG_ERROR, "only rectangular vol supported\n");

     if (ctx->shape == GRAY_SHAPE && vo_ver_id != 1) {

         av_log(s->avctx, AV_LOG_ERROR, "Gray shape not supported\n");

         skip_bits(gb, 4);  /* video_object_layer_shape_extension */

     }
 

     check_marker(s->avctx, gb, "before time_increment_resolution");

     s->avctx->framerate.num = get_bits(gb, 16);
     if (!s->avctx->framerate.num) {
         av_log(s->avctx, AV_LOG_ERROR, "framerate==0\n");

         return AVERROR_INVALIDDATA;

     }
 

     ctx->time_increment_bits = av_log2(s->avctx->framerate.num - 1) + 1;

     if (ctx->time_increment_bits < 1)
         ctx->time_increment_bits = 1;

     check_marker(s->avctx, gb, "before fixed_vop_rate");

     if (get_bits1(gb) != 0)     /* fixed_vop_rate  */

         s->avctx->framerate.den = get_bits(gb, ctx->time_increment_bits);

     else

         s->avctx->framerate.den = 1;

     s->avctx->time_base = av_inv_q(av_mul_q(s->avctx->framerate, (AVRational){s->avctx->ticks_per_frame, 1}));

     ctx->t_frame = 0;

     if (ctx->shape != BIN_ONLY_SHAPE) {
         if (ctx->shape == RECT_SHAPE) {

             check_marker(s->avctx, gb, "before width");

             width = get_bits(gb, 13);

             check_marker(s->avctx, gb, "before height");

             height = get_bits(gb, 13);

             check_marker(s->avctx, gb, "after height");

             if (width && height &&  /* they should be non zero but who knows */
                 !(s->width && s->codec_tag == AV_RL32("MP4S"))) {

                 if (s->width && s->height &&
                     (s->width != width || s->height != height))
                     s->context_reinit = 1;

                 s->width  = width;

                 s->height = height;
             }
         }
 

         s->progressive_sequence  =
         s->progressive_frame     = get_bits1(gb) ^ 1;
         s->interlaced_dct        = 0;
         if (!get_bits1(gb) && (s->avctx->debug & FF_DEBUG_PICT_INFO))
             av_log(s->avctx, AV_LOG_INFO,           /* OBMC Disable */

                    "MPEG-4 OBMC not supported (very likely buggy encoder)\n");

         if (vo_ver_id == 1)

             ctx->vol_sprite_usage = get_bits1(gb);    /* vol_sprite_usage */

         else

             ctx->vol_sprite_usage = get_bits(gb, 2);  /* vol_sprite_usage */

         if (ctx->vol_sprite_usage == STATIC_SPRITE)

             av_log(s->avctx, AV_LOG_ERROR, "Static Sprites not supported\n");

         if (ctx->vol_sprite_usage == STATIC_SPRITE ||
             ctx->vol_sprite_usage == GMC_SPRITE) {
             if (ctx->vol_sprite_usage == STATIC_SPRITE) {

                 skip_bits(gb, 13); // sprite_width

                 check_marker(s->avctx, gb, "after sprite_width");

                 skip_bits(gb, 13); // sprite_height

                 check_marker(s->avctx, gb, "after sprite_height");

                 skip_bits(gb, 13); // sprite_left

                 check_marker(s->avctx, gb, "after sprite_left");

                 skip_bits(gb, 13); // sprite_top

                 check_marker(s->avctx, gb, "after sprite_top");

             }

             ctx->num_sprite_warping_points = get_bits(gb, 6);
             if (ctx->num_sprite_warping_points > 3) {

                 av_log(s->avctx, AV_LOG_ERROR,
                        "%d sprite_warping_points\n",

                        ctx->num_sprite_warping_points);
                 ctx->num_sprite_warping_points = 0;

                 return AVERROR_INVALIDDATA;

             }

             s->sprite_warping_accuracy  = get_bits(gb, 2);

             ctx->sprite_brightness_change = get_bits1(gb);

             if (ctx->vol_sprite_usage == STATIC_SPRITE)

                 skip_bits1(gb); // low_latency_sprite

         }
         // FIXME sadct disable bit if verid!=1 && shape not rect
 

         if (get_bits1(gb) == 1) {                   /* not_8_bit */
             s->quant_precision = get_bits(gb, 4);   /* quant_precision */
             if (get_bits(gb, 4) != 8)               /* bits_per_pixel */
                 av_log(s->avctx, AV_LOG_ERROR, "N-bit not supported\n");
             if (s->quant_precision != 5)
                 av_log(s->avctx, AV_LOG_ERROR,
                        "quant precision %d\n", s->quant_precision);

             if (s->quant_precision<3 || s->quant_precision>9) {

                 s->quant_precision = 5;
             }

         } else {
             s->quant_precision = 5;
         }
 
         // FIXME a bunch of grayscale shape things
 

         if ((s->mpeg_quant = get_bits1(gb))) { /* vol_quant_type */

             int i, v;
 

             mpeg4_load_default_matrices(s);

 
             /* load custom intra matrix */

             if (get_bits1(gb)) {
                 int last = 0;
                 for (i = 0; i < 64; i++) {

                     int j;

                     if (get_bits_left(gb) < 8) {
                         av_log(s->avctx, AV_LOG_ERROR, "insufficient data for custom matrix\n");
                         return AVERROR_INVALIDDATA;
                     }

                     v = get_bits(gb, 8);
                     if (v == 0)
                         break;
 
                     last = v;

                     j = s->idsp.idct_permutation[ff_zigzag_direct[i]];

                     s->intra_matrix[j]        = last;
                     s->chroma_intra_matrix[j] = last;

                 }
 
                 /* replicate last value */

                 for (; i < 64; i++) {

                     int j = s->idsp.idct_permutation[ff_zigzag_direct[i]];

                     s->intra_matrix[j]        = last;
                     s->chroma_intra_matrix[j] = last;

                 }
             }
 
             /* load custom non intra matrix */

             if (get_bits1(gb)) {
                 int last = 0;
                 for (i = 0; i < 64; i++) {

                     int j;

                     if (get_bits_left(gb) < 8) {
                         av_log(s->avctx, AV_LOG_ERROR, "insufficient data for custom matrix\n");
                         return AVERROR_INVALIDDATA;
                     }

                     v = get_bits(gb, 8);
                     if (v == 0)
                         break;
 
                     last = v;

                     j = s->idsp.idct_permutation[ff_zigzag_direct[i]];

                     s->inter_matrix[j]        = v;
                     s->chroma_inter_matrix[j] = v;

                 }
 
                 /* replicate last value */

                 for (; i < 64; i++) {

                     int j = s->idsp.idct_permutation[ff_zigzag_direct[i]];

                     s->inter_matrix[j]        = last;
                     s->chroma_inter_matrix[j] = last;

                 }
             }
 
             // FIXME a bunch of grayscale shape things
         }
 

         if (vo_ver_id != 1)
             s->quarter_sample = get_bits1(gb);
         else
             s->quarter_sample = 0;
 

         if (get_bits_left(gb) < 4) {
             av_log(s->avctx, AV_LOG_ERROR, "VOL Header truncated\n");
             return AVERROR_INVALIDDATA;
         }
 

         if (!get_bits1(gb)) {
             int pos               = get_bits_count(gb);
             int estimation_method = get_bits(gb, 2);
             if (estimation_method < 2) {
                 if (!get_bits1(gb)) {

                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* opaque */
                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* transparent */
                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* intra_cae */
                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* inter_cae */
                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* no_update */

                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* upsampling */

                 }

                 if (!get_bits1(gb)) {

                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* intra_blocks */
                     ctx->cplx_estimation_trash_p += 8 * get_bits1(gb);  /* inter_blocks */
                     ctx->cplx_estimation_trash_p += 8 * get_bits1(gb);  /* inter4v_blocks */
                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* not coded blocks */

                 }

                 if (!check_marker(s->avctx, gb, "in complexity estimation part 1")) {

                     skip_bits_long(gb, pos - get_bits_count(gb));
                     goto no_cplx_est;
                 }

                 if (!get_bits1(gb)) {

                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* dct_coeffs */
                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* dct_lines */
                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* vlc_syms */
                     ctx->cplx_estimation_trash_i += 4 * get_bits1(gb);  /* vlc_bits */

                 }

                 if (!get_bits1(gb)) {

                     ctx->cplx_estimation_trash_p += 8 * get_bits1(gb);  /* apm */
                     ctx->cplx_estimation_trash_p += 8 * get_bits1(gb);  /* npm */
                     ctx->cplx_estimation_trash_b += 8 * get_bits1(gb);  /* interpolate_mc_q */
                     ctx->cplx_estimation_trash_p += 8 * get_bits1(gb);  /* forwback_mc_q */
                     ctx->cplx_estimation_trash_p += 8 * get_bits1(gb);  /* halfpel2 */
                     ctx->cplx_estimation_trash_p += 8 * get_bits1(gb);  /* halfpel4 */

                 }

                 if (!check_marker(s->avctx, gb, "in complexity estimation part 2")) {

                     skip_bits_long(gb, pos - get_bits_count(gb));
                     goto no_cplx_est;
                 }

                 if (estimation_method == 1) {

                     ctx->cplx_estimation_trash_i += 8 * get_bits1(gb);  /* sadct */
                     ctx->cplx_estimation_trash_p += 8 * get_bits1(gb);  /* qpel */

                 }

             } else
                 av_log(s->avctx, AV_LOG_ERROR,
                        "Invalid Complexity estimation method %d\n",
                        estimation_method);
         } else {
 

 no_cplx_est:

             ctx->cplx_estimation_trash_i =
             ctx->cplx_estimation_trash_p =
             ctx->cplx_estimation_trash_b = 0;

         }
 

         ctx->resync_marker = !get_bits1(gb); /* resync_marker_disabled */

         s->data_partitioning = get_bits1(gb);
         if (s->data_partitioning)

             ctx->rvlc = get_bits1(gb);

         if (vo_ver_id != 1) {

             ctx->new_pred = get_bits1(gb);
             if (ctx->new_pred) {

                 av_log(s->avctx, AV_LOG_ERROR, "new pred not supported\n");
                 skip_bits(gb, 2); /* requested upstream message type */

                 skip_bits1(gb);   /* newpred segment type */

             }

             if (get_bits1(gb)) // reduced_res_vop

                 av_log(s->avctx, AV_LOG_ERROR,
                        "reduced resolution VOP not supported\n");
         } else {

             ctx->new_pred = 0;

         }
 

         ctx->scalability = get_bits1(gb);

         if (ctx->scalability) {

             GetBitContext bak = *gb;

             int h_sampling_factor_n;
             int h_sampling_factor_m;
             int v_sampling_factor_n;
             int v_sampling_factor_m;
 

             skip_bits1(gb);    // hierarchy_type

             skip_bits(gb, 4);  /* ref_layer_id */
             skip_bits1(gb);    /* ref_layer_sampling_dir */

             h_sampling_factor_n = get_bits(gb, 5);
             h_sampling_factor_m = get_bits(gb, 5);
             v_sampling_factor_n = get_bits(gb, 5);
             v_sampling_factor_m = get_bits(gb, 5);

             ctx->enhancement_type = get_bits1(gb);

 
             if (h_sampling_factor_n == 0 || h_sampling_factor_m == 0 ||
                 v_sampling_factor_n == 0 || v_sampling_factor_m == 0) {

                 /* illegal scalability header (VERY broken encoder),
                  * trying to workaround */

                 ctx->scalability = 0;

                 *gb            = bak;
             } else

                 av_log(s->avctx, AV_LOG_ERROR, "scalability not supported\n");
 
             // bin shape stuff FIXME
         }
     }

     if (s->avctx->debug&FF_DEBUG_PICT_INFO) {

         av_log(s->avctx, AV_LOG_DEBUG, "tb %d/%d, tincrbits:%d, qp_prec:%d, ps:%d, low_delay:%d  %s%s%s%s\n",

                s->avctx->framerate.den, s->avctx->framerate.num,

                ctx->time_increment_bits,

                s->quant_precision,
                s->progressive_sequence,

                s->low_delay,

                ctx->scalability ? "scalability " :"" , s->quarter_sample ? "qpel " : "",

                s->data_partitioning ? "partition " : "", ctx->rvlc ? "rvlc " : ""

         );
     }
 

     return 0;
 }
 
 /**

  * Decode the user data stuff in the header.

  * Also initializes divx/xvid/lavc_version/build.
  */

 static int decode_user_data(Mpeg4DecContext *ctx, GetBitContext *gb)

 {

     MpegEncContext *s = &ctx->m;

     char buf[256];
     int i;
     int e;
     int ver = 0, build = 0, ver2 = 0, ver3 = 0;
     char last;
 

     for (i = 0; i < 255 && get_bits_count(gb) < gb->size_in_bits; i++) {
         if (show_bits(gb, 23) == 0)
             break;
         buf[i] = get_bits(gb, 8);

     }

     buf[i] = 0;

 
     /* divx detection */

     e = sscanf(buf, "DivX%dBuild%d%c", &ver, &build, &last);
     if (e < 2)
         e = sscanf(buf, "DivX%db%d%c", &ver, &build, &last);
     if (e >= 2) {

         ctx->divx_version = ver;
         ctx->divx_build   = build;

         s->divx_packed  = e == 3 && last == 'p';

     }
 

     /* libavcodec detection */

     e = sscanf(buf, "FFmpe%*[^b]b%d", &build) + 3;
     if (e != 4)
         e = sscanf(buf, "FFmpeg v%d.%d.%d / libavcodec build: %d", &ver, &ver2, &ver3, &build);
     if (e != 4) {
         e = sscanf(buf, "Lavc%d.%d.%d", &ver, &ver2, &ver3) + 1;

         if (e > 1) {

             if (ver > 0xFFU || ver2 > 0xFFU || ver3 > 0xFFU) {

                 av_log(s->avctx, AV_LOG_WARNING,
                      "Unknown Lavc version string encountered, %d.%d.%d; "
                      "clamping sub-version values to 8-bits.\n",
                      ver, ver2, ver3);
             }
             build = ((ver & 0xFF) << 16) + ((ver2 & 0xFF) << 8) + (ver3 & 0xFF);
         }

     }

     if (e != 4) {
         if (strcmp(buf, "ffmpeg") == 0)

             ctx->lavc_build = 4600;

     }

     if (e == 4)

         ctx->lavc_build = build;

 
     /* Xvid detection */

     e = sscanf(buf, "XviD%d", &build);
     if (e == 1)

         ctx->xvid_build = build;

 
     return 0;
 }
 

 int ff_mpeg4_workaround_bugs(AVCodecContext *avctx)
 {
     Mpeg4DecContext *ctx = avctx->priv_data;
     MpegEncContext *s = &ctx->m;
 

     if (ctx->xvid_build == -1 && ctx->divx_version == -1 && ctx->lavc_build == -1) {

         if (s->codec_tag        == AV_RL32("XVID") ||

             s->codec_tag        == AV_RL32("XVIX") ||
             s->codec_tag        == AV_RL32("RMP4") ||
             s->codec_tag        == AV_RL32("ZMP4") ||
             s->codec_tag        == AV_RL32("SIPP"))

             ctx->xvid_build = 0;

     }
 

     if (ctx->xvid_build == -1 && ctx->divx_version == -1 && ctx->lavc_build == -1)

         if (s->codec_tag == AV_RL32("DIVX") && s->vo_type == 0 &&

             ctx->vol_control_parameters == 0)

             ctx->divx_version = 400;  // divx 4

     if (ctx->xvid_build >= 0 && ctx->divx_version >= 0) {
         ctx->divx_version =
         ctx->divx_build   = -1;

     }
 
     if (s->workaround_bugs & FF_BUG_AUTODETECT) {
         if (s->codec_tag == AV_RL32("XVIX"))
             s->workaround_bugs |= FF_BUG_XVID_ILACE;
 
         if (s->codec_tag == AV_RL32("UMP4"))
             s->workaround_bugs |= FF_BUG_UMP4;
 

         if (ctx->divx_version >= 500 && ctx->divx_build < 1814)

             s->workaround_bugs |= FF_BUG_QPEL_CHROMA;
 

         if (ctx->divx_version > 502 && ctx->divx_build < 1814)

             s->workaround_bugs |= FF_BUG_QPEL_CHROMA2;
 

         if (ctx->xvid_build <= 3U)

             s->padding_bug_score = 256 * 256 * 256 * 64;
 

         if (ctx->xvid_build <= 1U)

             s->workaround_bugs |= FF_BUG_QPEL_CHROMA;
 

         if (ctx->xvid_build <= 12U)

             s->workaround_bugs |= FF_BUG_EDGE;
 

         if (ctx->xvid_build <= 32U)

             s->workaround_bugs |= FF_BUG_DC_CLIP;
 
 #define SET_QPEL_FUNC(postfix1, postfix2)                           \

     s->qdsp.put_        ## postfix1 = ff_put_        ## postfix2;   \
     s->qdsp.put_no_rnd_ ## postfix1 = ff_put_no_rnd_ ## postfix2;   \
     s->qdsp.avg_        ## postfix1 = ff_avg_        ## postfix2;

         if (ctx->lavc_build < 4653U)

             s->workaround_bugs |= FF_BUG_STD_QPEL;
 

         if (ctx->lavc_build < 4655U)

             s->workaround_bugs |= FF_BUG_DIRECT_BLOCKSIZE;
 

         if (ctx->lavc_build < 4670U)

             s->workaround_bugs |= FF_BUG_EDGE;
 

         if (ctx->lavc_build <= 4712U)

             s->workaround_bugs |= FF_BUG_DC_CLIP;
 

         if ((ctx->lavc_build&0xFF) >= 100) {
             if (ctx->lavc_build > 3621476 && ctx->lavc_build < 3752552 &&
                (ctx->lavc_build < 3752037 || ctx->lavc_build > 3752191) // 3.2.1+
             )
                 s->workaround_bugs |= FF_BUG_IEDGE;
         }
 

         if (ctx->divx_version >= 0)

             s->workaround_bugs |= FF_BUG_DIRECT_BLOCKSIZE;

         if (ctx->divx_version == 501 && ctx->divx_build == 20020416)

             s->padding_bug_score = 256 * 256 * 256 * 64;
 

         if (ctx->divx_version < 500U)

             s->workaround_bugs |= FF_BUG_EDGE;
 

         if (ctx->divx_version >= 0)

             s->workaround_bugs |= FF_BUG_HPEL_CHROMA;
     }
 
     if (s->workaround_bugs & FF_BUG_STD_QPEL) {
         SET_QPEL_FUNC(qpel_pixels_tab[0][5], qpel16_mc11_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[0][7], qpel16_mc31_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[0][9], qpel16_mc12_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[0][11], qpel16_mc32_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[0][13], qpel16_mc13_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[0][15], qpel16_mc33_old_c)
 
         SET_QPEL_FUNC(qpel_pixels_tab[1][5], qpel8_mc11_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[1][7], qpel8_mc31_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[1][9], qpel8_mc12_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[1][11], qpel8_mc32_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[1][13], qpel8_mc13_old_c)
         SET_QPEL_FUNC(qpel_pixels_tab[1][15], qpel8_mc33_old_c)
     }
 
     if (avctx->debug & FF_DEBUG_BUGS)
         av_log(s->avctx, AV_LOG_DEBUG,
                "bugs: %X lavc_build:%d xvid_build:%d divx_version:%d divx_build:%d %s\n",

                s->workaround_bugs, ctx->lavc_build, ctx->xvid_build,
                ctx->divx_version, ctx->divx_build, s->divx_packed ? "p" : "");

     if (CONFIG_MPEG4_DECODER && ctx->xvid_build >= 0 &&
         s->codec_id == AV_CODEC_ID_MPEG4 &&

         avctx->idct_algo == FF_IDCT_AUTO) {

         avctx->idct_algo = FF_IDCT_XVID;

         ff_mpv_idct_init(s);

         return 1;
     }

     return 0;
 }
 

 static int decode_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb)

 {

     MpegEncContext *s = &ctx->m;

     int time_incr, time_increment;

     int64_t pts;

     s->mcsel       = 0;

     s->pict_type = get_bits(gb, 2) + AV_PICTURE_TYPE_I;        /* pict type: I = 0 , P = 1 */

     if (s->pict_type == AV_PICTURE_TYPE_B && s->low_delay &&

         ctx->vol_control_parameters == 0 && !(s->avctx->flags & AV_CODEC_FLAG_LOW_DELAY)) {

         av_log(s->avctx, AV_LOG_ERROR, "low_delay flag set incorrectly, clearing it\n");

         s->low_delay = 0;

     }
 

     s->partitioned_frame = s->data_partitioning && s->pict_type != AV_PICTURE_TYPE_B;
     if (s->partitioned_frame)
         s->decode_mb = mpeg4_decode_partitioned_mb;

     else

         s->decode_mb = mpeg4_decode_mb;

     time_incr = 0;

     while (get_bits1(gb) != 0)
         time_incr++;
 

     check_marker(s->avctx, gb, "before time_increment");

     if (ctx->time_increment_bits == 0 ||
         !(show_bits(gb, ctx->time_increment_bits + 1) & 1)) {

         av_log(s->avctx, AV_LOG_WARNING,

                "time_increment_bits %d is invalid in relation to the current bitstream, this is likely caused by a missing VOL header\n", ctx->time_increment_bits);

         for (ctx->time_increment_bits = 1;
              ctx->time_increment_bits < 16;
              ctx->time_increment_bits++) {

             if (s->pict_type == AV_PICTURE_TYPE_P ||
                 (s->pict_type == AV_PICTURE_TYPE_S &&

                  ctx->vol_sprite_usage == GMC_SPRITE)) {

                 if ((show_bits(gb, ctx->time_increment_bits + 6) & 0x37) == 0x30)

                     break;

             } else if ((show_bits(gb, ctx->time_increment_bits + 5) & 0x1F) == 0x18)

                 break;

         }
 

         av_log(s->avctx, AV_LOG_WARNING,

                "time_increment_bits set to %d bits, based on bitstream analysis\n", ctx->time_increment_bits);

         if (s->avctx->framerate.num && 4*s->avctx->framerate.num < 1<<ctx->time_increment_bits) {
             s->avctx->framerate.num = 1<<ctx->time_increment_bits;
             s->avctx->time_base = av_inv_q(av_mul_q(s->avctx->framerate, (AVRational){s->avctx->ticks_per_frame, 1}));

         }

     }
 

     if (IS_3IV1)
         time_increment = get_bits1(gb);        // FIXME investigate further
     else

         time_increment = get_bits(gb, ctx->time_increment_bits);

 
     if (s->pict_type != AV_PICTURE_TYPE_B) {
         s->last_time_base = s->time_base;
         s->time_base     += time_incr;

         s->time = s->time_base * (int64_t)s->avctx->framerate.num + time_increment;

         if (s->workaround_bugs & FF_BUG_UMP4) {
             if (s->time < s->last_non_b_time) {

                 /* header is not mpeg-4-compatible, broken encoder,
                  * trying to workaround */
                 s->time_base++;

                 s->time += s->avctx->framerate.num;

             }
         }

         s->pp_time         = s->time - s->last_non_b_time;
         s->last_non_b_time = s->time;
     } else {

         s->time    = (s->last_time_base + time_incr) * (int64_t)s->avctx->framerate.num + time_increment;

         s->pb_time = s->pp_time - (s->last_non_b_time - s->time);
         if (s->pp_time <= s->pb_time ||
             s->pp_time <= s->pp_time - s->pb_time ||
             s->pp_time <= 0) {

             /* messed up order, maybe after seeking? skipping current B-frame */

             return FRAME_SKIPPED;
         }
         ff_mpeg4_init_direct_mv(s);
 

         if (ctx->t_frame == 0)
             ctx->t_frame = s->pb_time;
         if (ctx->t_frame == 0)
             ctx->t_frame = 1;  // 1/0 protection
         s->pp_field_time = (ROUNDED_DIV(s->last_non_b_time, ctx->t_frame) -
                             ROUNDED_DIV(s->last_non_b_time - s->pp_time, ctx->t_frame)) * 2;
         s->pb_field_time = (ROUNDED_DIV(s->time, ctx->t_frame) -
                             ROUNDED_DIV(s->last_non_b_time - s->pp_time, ctx->t_frame)) * 2;

         if (s->pp_field_time <= s->pb_field_time || s->pb_field_time <= 1) {
             s->pb_field_time = 2;
             s->pp_field_time = 4;
             if (!s->progressive_sequence)

                 return FRAME_SKIPPED;
         }
     }
 

     if (s->avctx->framerate.den)
         pts = ROUNDED_DIV(s->time, s->avctx->framerate.den);

     else

         pts = AV_NOPTS_VALUE;

     ff_dlog(s->avctx, "MPEG4 PTS: %"PRId64"\n", pts);

     check_marker(s->avctx, gb, "before vop_coded");

 
     /* vop coded */

     if (get_bits1(gb) != 1) {
         if (s->avctx->debug & FF_DEBUG_PICT_INFO)

             av_log(s->avctx, AV_LOG_ERROR, "vop not coded\n");
         return FRAME_SKIPPED;
     }

     if (ctx->new_pred)

         decode_new_pred(ctx, gb);

     if (ctx->shape != BIN_ONLY_SHAPE &&

                     (s->pict_type == AV_PICTURE_TYPE_P ||
                      (s->pict_type == AV_PICTURE_TYPE_S &&

                       ctx->vol_sprite_usage == GMC_SPRITE))) {

         /* rounding type for motion estimation */
         s->no_rounding = get_bits1(gb);
     } else {
         s->no_rounding = 0;
     }

     // FIXME reduced res stuff
 

     if (ctx->shape != RECT_SHAPE) {

         if (ctx->vol_sprite_usage != 1 || s->pict_type != AV_PICTURE_TYPE_I) {

             skip_bits(gb, 13);  /* width */

             check_marker(s->avctx, gb, "after width");

             skip_bits(gb, 13);  /* height */

             check_marker(s->avctx, gb, "after height");

             skip_bits(gb, 13);  /* hor_spat_ref */

             check_marker(s->avctx, gb, "after hor_spat_ref");

             skip_bits(gb, 13);  /* ver_spat_ref */
         }
         skip_bits1(gb);         /* change_CR_disable */
 
         if (get_bits1(gb) != 0)
             skip_bits(gb, 8);   /* constant_alpha_value */
     }
 
     // FIXME complexity estimation stuff
 

     if (ctx->shape != BIN_ONLY_SHAPE) {

         skip_bits_long(gb, ctx->cplx_estimation_trash_i);

         if (s->pict_type != AV_PICTURE_TYPE_I)

             skip_bits_long(gb, ctx->cplx_estimation_trash_p);

         if (s->pict_type == AV_PICTURE_TYPE_B)

             skip_bits_long(gb, ctx->cplx_estimation_trash_b);

         if (get_bits_left(gb) < 3) {
             av_log(s->avctx, AV_LOG_ERROR, "Header truncated\n");

             return AVERROR_INVALIDDATA;

         }

         ctx->intra_dc_threshold = ff_mpeg4_dc_threshold[get_bits(gb, 3)];

         if (!s->progressive_sequence) {
             s->top_field_first = get_bits1(gb);
             s->alternate_scan  = get_bits1(gb);
         } else
             s->alternate_scan = 0;
     }
 
     if (s->alternate_scan) {

         ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable,   ff_alternate_vertical_scan);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable,   ff_alternate_vertical_scan);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_h_scantable, ff_alternate_vertical_scan);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_v_scantable, ff_alternate_vertical_scan);

     } else {

         ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable,   ff_zigzag_direct);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable,   ff_zigzag_direct);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_h_scantable, ff_alternate_horizontal_scan);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_v_scantable, ff_alternate_vertical_scan);

     }
 

     if (s->pict_type == AV_PICTURE_TYPE_S) {
         if((ctx->vol_sprite_usage == STATIC_SPRITE ||
             ctx->vol_sprite_usage == GMC_SPRITE)) {
             if (mpeg4_decode_sprite_trajectory(ctx, gb) < 0)
                 return AVERROR_INVALIDDATA;
             if (ctx->sprite_brightness_change)
                 av_log(s->avctx, AV_LOG_ERROR,
                     "sprite_brightness_change not supported\n");
             if (ctx->vol_sprite_usage == STATIC_SPRITE)
                 av_log(s->avctx, AV_LOG_ERROR, "static sprite not supported\n");
         } else {
             memset(s->sprite_offset, 0, sizeof(s->sprite_offset));
             memset(s->sprite_delta, 0, sizeof(s->sprite_delta));
         }

     }
 

     if (ctx->shape != BIN_ONLY_SHAPE) {

         s->chroma_qscale = s->qscale = get_bits(gb, s->quant_precision);
         if (s->qscale == 0) {
             av_log(s->avctx, AV_LOG_ERROR,

                    "Error, header damaged or not MPEG-4 header (qscale=0)\n");

             return AVERROR_INVALIDDATA;  // makes no sense to continue, as there is nothing left from the image then

         }
 
         if (s->pict_type != AV_PICTURE_TYPE_I) {
             s->f_code = get_bits(gb, 3);        /* fcode_for */
             if (s->f_code == 0) {
                 av_log(s->avctx, AV_LOG_ERROR,

                        "Error, header damaged or not MPEG-4 header (f_code=0)\n");

                 s->f_code = 1;

                 return AVERROR_INVALIDDATA;  // makes no sense to continue, as there is nothing left from the image then

             }
         } else
             s->f_code = 1;
 
         if (s->pict_type == AV_PICTURE_TYPE_B) {
             s->b_code = get_bits(gb, 3);

             if (s->b_code == 0) {
                 av_log(s->avctx, AV_LOG_ERROR,
                        "Error, header damaged or not MPEG4 header (b_code=0)\n");
                 s->b_code=1;

                 return AVERROR_INVALIDDATA; // makes no sense to continue, as the MV decoding will break very quickly

             }

         } else
             s->b_code = 1;
 
         if (s->avctx->debug & FF_DEBUG_PICT_INFO) {
             av_log(s->avctx, AV_LOG_DEBUG,

                    "qp:%d fc:%d,%d %s size:%d pro:%d alt:%d top:%d %spel part:%d resync:%d w:%d a:%d rnd:%d vot:%d%s dc:%d ce:%d/%d/%d time:%"PRId64" tincr:%d\n",

                    s->qscale, s->f_code, s->b_code,
                    s->pict_type == AV_PICTURE_TYPE_I ? "I" : (s->pict_type == AV_PICTURE_TYPE_P ? "P" : (s->pict_type == AV_PICTURE_TYPE_B ? "B" : "S")),

                    gb->size_in_bits,s->progressive_sequence, s->alternate_scan,

                    s->top_field_first, s->quarter_sample ? "q" : "h",

                    s->data_partitioning, ctx->resync_marker,

                    ctx->num_sprite_warping_points, s->sprite_warping_accuracy,

                    1 - s->no_rounding, s->vo_type,

                    ctx->vol_control_parameters ? " VOLC" : " ", ctx->intra_dc_threshold,

                    ctx->cplx_estimation_trash_i, ctx->cplx_estimation_trash_p,

                    ctx->cplx_estimation_trash_b,

                    s->time,
                    time_increment
                   );

         }
 

         if (!ctx->scalability) {

             if (ctx->shape != RECT_SHAPE && s->pict_type != AV_PICTURE_TYPE_I)

                 skip_bits1(gb);  // vop shape coding type
         } else {

             if (ctx->enhancement_type) {

                 int load_backward_shape = get_bits1(gb);
                 if (load_backward_shape)
                     av_log(s->avctx, AV_LOG_ERROR,
                            "load backward shape isn't supported\n");
             }
             skip_bits(gb, 2);  // ref_select_code
         }
     }
     /* detect buggy encoders which don't set the low_delay flag

      * (divx4/xvid/opendivx). Note we cannot detect divx5 without B-frames

      * easily (although it's buggy too) */

     if (s->vo_type == 0 && ctx->vol_control_parameters == 0 &&

         ctx->divx_version == -1 && s->picture_number == 0) {

         av_log(s->avctx, AV_LOG_WARNING,
                "looks like this file was encoded with (divx4/(old)xvid/opendivx) -> forcing low_delay flag\n");
         s->low_delay = 1;
     }
 
     s->picture_number++;  // better than pic number==0 always ;)
 
     // FIXME add short header support
     s->y_dc_scale_table = ff_mpeg4_y_dc_scale_table;
     s->c_dc_scale_table = ff_mpeg4_c_dc_scale_table;
 
     if (s->workaround_bugs & FF_BUG_EDGE) {
         s->h_edge_pos = s->width;
         s->v_edge_pos = s->height;
     }
     return 0;

 }
 

 static void read_quant_matrix_ext(MpegEncContext *s, GetBitContext *gb)
 {
     int i, j, v;
 
     if (get_bits1(gb)) {
         /* intra_quantiser_matrix */
         for (i = 0; i < 64; i++) {
             v = get_bits(gb, 8);
             j = s->idsp.idct_permutation[ff_zigzag_direct[i]];
             s->intra_matrix[j]        = v;
             s->chroma_intra_matrix[j] = v;
         }
     }
 
     if (get_bits1(gb)) {
         /* non_intra_quantiser_matrix */
         for (i = 0; i < 64; i++) {
             get_bits(gb, 8);
         }
     }
 
     if (get_bits1(gb)) {
         /* chroma_intra_quantiser_matrix */
         for (i = 0; i < 64; i++) {
             v = get_bits(gb, 8);
             j = s->idsp.idct_permutation[ff_zigzag_direct[i]];
             s->chroma_intra_matrix[j] = v;
         }
     }
 
     if (get_bits1(gb)) {
         /* chroma_non_intra_quantiser_matrix */
         for (i = 0; i < 64; i++) {
             get_bits(gb, 8);
         }
     }
 
     next_start_code_studio(gb);
 }
 
 static void extension_and_user_data(MpegEncContext *s, GetBitContext *gb, int id)
 {
     uint32_t startcode;
     uint8_t extension_type;
 
     startcode = show_bits_long(gb, 32);
     if (startcode == USER_DATA_STARTCODE || startcode == EXT_STARTCODE) {
 
         if ((id == 2 || id == 4) && startcode == EXT_STARTCODE) {
             skip_bits_long(gb, 32);
             extension_type = get_bits(gb, 4);
             if (extension_type == QUANT_MATRIX_EXT_ID)
                 read_quant_matrix_ext(s, gb);
         }
     }
 }
 
 static void decode_smpte_tc(Mpeg4DecContext *ctx, GetBitContext *gb)
 {
     MpegEncContext *s = &ctx->m;
 
     skip_bits(gb, 16); /* Time_code[63..48] */
     check_marker(s->avctx, gb, "after Time_code[63..48]");
     skip_bits(gb, 16); /* Time_code[47..32] */
     check_marker(s->avctx, gb, "after Time_code[47..32]");
     skip_bits(gb, 16); /* Time_code[31..16] */
     check_marker(s->avctx, gb, "after Time_code[31..16]");
     skip_bits(gb, 16); /* Time_code[15..0] */
     check_marker(s->avctx, gb, "after Time_code[15..0]");
     skip_bits(gb, 4); /* reserved_bits */
 }
 
 /**
  * Decode the next studio vop header.
  * @return <0 if something went wrong
  */
 static int decode_studio_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb)
 {
     MpegEncContext *s = &ctx->m;
 
     if (get_bits_left(gb) <= 32)
         return 0;
 
     if (get_bits_long(gb, 32) != VOP_STARTCODE)
         return AVERROR_INVALIDDATA;
 
     s->decode_mb = mpeg4_decode_studio_mb;
 
     decode_smpte_tc(ctx, gb);
 
     skip_bits(gb, 10); /* temporal_reference */
     skip_bits(gb, 2); /* vop_structure */
     s->pict_type = get_bits(gb, 2) + AV_PICTURE_TYPE_I; /* vop_coding_type */
     if (get_bits1(gb)) { /* vop_coded */
         skip_bits1(gb); /* top_field_first */
         skip_bits1(gb); /* repeat_first_field */
         s->progressive_frame = get_bits1(gb) ^ 1; /* progressive_frame */
     }
 
     if (s->pict_type == AV_PICTURE_TYPE_I) {
         if (get_bits1(gb))
             reset_studio_dc_predictors(s);
     }
 
     if (ctx->shape != BIN_ONLY_SHAPE) {
         s->alternate_scan = get_bits1(gb);
         s->frame_pred_frame_dct = get_bits1(gb);
         s->dct_precision = get_bits(gb, 2);
         s->intra_dc_precision = get_bits(gb, 2);
         s->q_scale_type = get_bits1(gb);
     }
 
     if (s->alternate_scan) {
         ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable,   ff_alternate_vertical_scan);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable,   ff_alternate_vertical_scan);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_h_scantable, ff_alternate_vertical_scan);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_v_scantable, ff_alternate_vertical_scan);
     } else {
         ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable,   ff_zigzag_direct);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable,   ff_zigzag_direct);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_h_scantable, ff_alternate_horizontal_scan);
         ff_init_scantable(s->idsp.idct_permutation, &s->intra_v_scantable, ff_alternate_vertical_scan);
     }
 
     mpeg4_load_default_matrices(s);
 
     next_start_code_studio(gb);
     extension_and_user_data(s, gb, 4);
 
     return 0;
 }
 
 static int decode_studiovisualobject(Mpeg4DecContext *ctx, GetBitContext *gb)
 {
     uint32_t startcode;
     MpegEncContext *s = &ctx->m;
     int visual_object_type, width, height;
 
     startcode = get_bits_long(gb, 32);
 
     /* StudioVisualObject() */
     if (startcode == VISUAL_OBJ_STARTCODE) {
         skip_bits(gb, 4); /* visual_object_verid */
         visual_object_type = get_bits(gb, 4);
 
         next_start_code_studio(gb);
         extension_and_user_data(s, gb, 1);
 
         if (visual_object_type == VOT_VIDEO_ID) {
             /* StudioVideoObjectLayer */
             skip_bits_long(gb, 32); /* video_object_start_code */
             skip_bits_long(gb, 32); /* video_object_layer_start_code */
             skip_bits1(gb); /* random_accessible_vol */
             skip_bits(gb, 8); /* video_object_type_indication */
             skip_bits(gb, 4); /* video_object_layer_verid */
             ctx->shape = get_bits(gb, 2); /* video_object_layer_shape */
             skip_bits(gb, 4); /* video_object_layer_shape_extension */
             skip_bits1(gb); /* progressive_sequence */
             if (ctx->shape != BIN_ONLY_SHAPE) {
                 ctx->rgb = get_bits1(gb); /* rgb_components */
                 s->chroma_format = get_bits(gb, 2); /* chroma_format */
                 if (!s->chroma_format) {
                     av_log(s->avctx, AV_LOG_ERROR, "illegal chroma format\n");
                     return AVERROR_INVALIDDATA;
                 }
 
                 s->avctx->bits_per_raw_sample = get_bits(gb, 4); /* bit_depth */
                 if (s->avctx->bits_per_raw_sample == 10) {
                     if (ctx->rgb) {
                         s->avctx->pix_fmt = AV_PIX_FMT_GBRP10;
                     }
                     else {
                         s->avctx->pix_fmt = s->chroma_format == CHROMA_422 ? AV_PIX_FMT_YUV422P10 : AV_PIX_FMT_YUV444P10;
                     }
                 }
                 else {
                     avpriv_request_sample(s->avctx, "MPEG-4 Studio profile bit-depth %u", s->avctx->bits_per_raw_sample);
                     return AVERROR_PATCHWELCOME;
                 }
             }
             if (ctx->shape == RECT_SHAPE) {
                 check_marker(s->avctx, gb, "before video_object_layer_width");
                 width = get_bits(gb, 14); /* video_object_layer_width */
                 check_marker(s->avctx, gb, "before video_object_layer_height");
                 height = get_bits(gb, 14); /* video_object_layer_height */
                 check_marker(s->avctx, gb, "after video_object_layer_height");
 
                 /* Do the same check as non-studio profile */
                 if (width && height) {
                     if (s->width && s->height &&
                         (s->width != width || s->height != height))
                         s->context_reinit = 1;
                     s->width  = width;
                     s->height = height;
                 }
             }
             s->aspect_ratio_info = get_bits(gb, 4);
             if (s->aspect_ratio_info == FF_ASPECT_EXTENDED) {
                 s->avctx->sample_aspect_ratio.num = get_bits(gb, 8);  // par_width
                 s->avctx->sample_aspect_ratio.den = get_bits(gb, 8);  // par_height
             } else {
                 s->avctx->sample_aspect_ratio = ff_h263_pixel_aspect[s->aspect_ratio_info];
             }
             skip_bits(gb, 4); /* frame_rate_code */
             skip_bits(gb, 15); /* first_half_bit_rate */
             check_marker(s->avctx, gb, "after first_half_bit_rate");
             skip_bits(gb, 15); /* latter_half_bit_rate */
             check_marker(s->avctx, gb, "after latter_half_bit_rate");
             skip_bits(gb, 15); /* first_half_vbv_buffer_size */
             check_marker(s->avctx, gb, "after first_half_vbv_buffer_size");
             skip_bits(gb, 3); /* latter_half_vbv_buffer_size */
             skip_bits(gb, 11); /* first_half_vbv_buffer_size */
             check_marker(s->avctx, gb, "after first_half_vbv_buffer_size");
             skip_bits(gb, 15); /* latter_half_vbv_occupancy */
             check_marker(s->avctx, gb, "after latter_half_vbv_occupancy");
             s->low_delay = get_bits1(gb);
             s->mpeg_quant = get_bits1(gb); /* mpeg2_stream */
 
             next_start_code_studio(gb);
             extension_and_user_data(s, gb, 2);
         }
     }
 
     return 0;
 }
 

 /**

  * Decode MPEG-4 headers.

  * @return <0 if no VOP found (or a damaged one)
  *         FRAME_SKIPPED if a not coded VOP is found
  *         0 if a VOP is found
  */

 int ff_mpeg4_decode_picture_header(Mpeg4DecContext *ctx, GetBitContext *gb)

 {

     MpegEncContext *s = &ctx->m;

     unsigned startcode, v;

     int ret;

     int vol = 0;

 
     /* search next start code */
     align_get_bits(gb);
 

     if (s->codec_tag == AV_RL32("WV1F") && show_bits(gb, 24) == 0x575630) {

         skip_bits(gb, 24);

         if (get_bits(gb, 8) == 0xF0)

             goto end;
     }
 
     startcode = 0xff;

     for (;;) {
         if (get_bits_count(gb) >= gb->size_in_bits) {
             if (gb->size_in_bits == 8 &&

                 (ctx->divx_version >= 0 || ctx->xvid_build >= 0) || s->codec_tag == AV_RL32("QMP4")) {

                 av_log(s->avctx, AV_LOG_VERBOSE, "frame skip %d\n", gb->size_in_bits);

                 return FRAME_SKIPPED;  // divx bug
             } else

                 return AVERROR_INVALIDDATA;  // end of stream

         }
 
         /* use the bits after the test */
         v = get_bits(gb, 8);
         startcode = ((startcode << 8) | v) & 0xffffffff;
 

         if ((startcode & 0xFFFFFF00) != 0x100)
             continue;  // no startcode

         if (s->avctx->debug & FF_DEBUG_STARTCODE) {

             av_log(s->avctx, AV_LOG_DEBUG, "startcode: %3X ", startcode);

             if (startcode <= 0x11F)
                 av_log(s->avctx, AV_LOG_DEBUG, "Video Object Start");
             else if (startcode <= 0x12F)
                 av_log(s->avctx, AV_LOG_DEBUG, "Video Object Layer Start");
             else if (startcode <= 0x13F)
                 av_log(s->avctx, AV_LOG_DEBUG, "Reserved");
             else if (startcode <= 0x15F)
                 av_log(s->avctx, AV_LOG_DEBUG, "FGS bp start");
             else if (startcode <= 0x1AF)
                 av_log(s->avctx, AV_LOG_DEBUG, "Reserved");
             else if (startcode == 0x1B0)
                 av_log(s->avctx, AV_LOG_DEBUG, "Visual Object Seq Start");
             else if (startcode == 0x1B1)
                 av_log(s->avctx, AV_LOG_DEBUG, "Visual Object Seq End");
             else if (startcode == 0x1B2)
                 av_log(s->avctx, AV_LOG_DEBUG, "User Data");
             else if (startcode == 0x1B3)
                 av_log(s->avctx, AV_LOG_DEBUG, "Group of VOP start");
             else if (startcode == 0x1B4)
                 av_log(s->avctx, AV_LOG_DEBUG, "Video Session Error");
             else if (startcode == 0x1B5)
                 av_log(s->avctx, AV_LOG_DEBUG, "Visual Object Start");
             else if (startcode == 0x1B6)
                 av_log(s->avctx, AV_LOG_DEBUG, "Video Object Plane start");
             else if (startcode == 0x1B7)
                 av_log(s->avctx, AV_LOG_DEBUG, "slice start");
             else if (startcode == 0x1B8)
                 av_log(s->avctx, AV_LOG_DEBUG, "extension start");
             else if (startcode == 0x1B9)
                 av_log(s->avctx, AV_LOG_DEBUG, "fgs start");
             else if (startcode == 0x1BA)
                 av_log(s->avctx, AV_LOG_DEBUG, "FBA Object start");
             else if (startcode == 0x1BB)
                 av_log(s->avctx, AV_LOG_DEBUG, "FBA Object Plane start");
             else if (startcode == 0x1BC)
                 av_log(s->avctx, AV_LOG_DEBUG, "Mesh Object start");
             else if (startcode == 0x1BD)
                 av_log(s->avctx, AV_LOG_DEBUG, "Mesh Object Plane start");
             else if (startcode == 0x1BE)
                 av_log(s->avctx, AV_LOG_DEBUG, "Still Texture Object start");
             else if (startcode == 0x1BF)
                 av_log(s->avctx, AV_LOG_DEBUG, "Texture Spatial Layer start");
             else if (startcode == 0x1C0)
                 av_log(s->avctx, AV_LOG_DEBUG, "Texture SNR Layer start");
             else if (startcode == 0x1C1)
                 av_log(s->avctx, AV_LOG_DEBUG, "Texture Tile start");
             else if (startcode == 0x1C2)
                 av_log(s->avctx, AV_LOG_DEBUG, "Texture Shape Layer start");
             else if (startcode == 0x1C3)
                 av_log(s->avctx, AV_LOG_DEBUG, "stuffing start");
             else if (startcode <= 0x1C5)
                 av_log(s->avctx, AV_LOG_DEBUG, "reserved");
             else if (startcode <= 0x1FF)
                 av_log(s->avctx, AV_LOG_DEBUG, "System start");

             av_log(s->avctx, AV_LOG_DEBUG, " at %d\n", get_bits_count(gb));
         }
 

         if (startcode >= 0x120 && startcode <= 0x12F) {

             if (vol) {

                 av_log(s->avctx, AV_LOG_WARNING, "Ignoring multiple VOL headers\n");
                 continue;

             }
             vol++;

             if ((ret = decode_vol_header(ctx, gb)) < 0)
                 return ret;

         } else if (startcode == USER_DATA_STARTCODE) {

             decode_user_data(ctx, gb);

         } else if (startcode == GOP_STARTCODE) {

             mpeg4_decode_gop_header(s, gb);

         } else if (startcode == VOS_STARTCODE) {

             mpeg4_decode_profile_level(s, gb);

             if (s->avctx->profile == FF_PROFILE_MPEG4_SIMPLE_STUDIO &&
                 (s->avctx->level > 0 && s->avctx->level < 9)) {
                 s->studio_profile = 1;
                 next_start_code_studio(gb);
                 extension_and_user_data(s, gb, 0);
 
                 if ((ret = decode_studiovisualobject(ctx, gb)) < 0)
                     return ret;
                 break;
             }

         } else if (startcode == VISUAL_OBJ_STARTCODE) {
             mpeg4_decode_visual_object(s, gb);

         } else if (startcode == VOP_STARTCODE) {

             break;
         }
 
         align_get_bits(gb);
         startcode = 0xff;
     }

 end:

     if (s->avctx->flags & AV_CODEC_FLAG_LOW_DELAY)

         s->low_delay = 1;
     s->avctx->has_b_frames = !s->low_delay;
 

     if (s->studio_profile)
         return decode_studio_vop_header(ctx, gb);
     else
         return decode_vop_header(ctx, gb);

 }
 

 av_cold void ff_mpeg4videodec_static_init(void) {

     static int done = 0;
 
     if (!done) {

         ff_rl_init(&ff_mpeg4_rl_intra, ff_mpeg4_static_rl_table_store[0]);
         ff_rl_init(&ff_rvlc_rl_inter, ff_mpeg4_static_rl_table_store[1]);
         ff_rl_init(&ff_rvlc_rl_intra, ff_mpeg4_static_rl_table_store[2]);

         INIT_VLC_RL(ff_mpeg4_rl_intra, 554);

         INIT_VLC_RL(ff_rvlc_rl_inter, 1072);
         INIT_VLC_RL(ff_rvlc_rl_intra, 1072);

         INIT_VLC_STATIC(&dc_lum, DC_VLC_BITS, 10 /* 13 */,

                         &ff_mpeg4_DCtab_lum[0][1], 2, 1,
                         &ff_mpeg4_DCtab_lum[0][0], 2, 1, 512);

         INIT_VLC_STATIC(&dc_chrom, DC_VLC_BITS, 10 /* 13 */,

                         &ff_mpeg4_DCtab_chrom[0][1], 2, 1,
                         &ff_mpeg4_DCtab_chrom[0][0], 2, 1, 512);

         INIT_VLC_STATIC(&sprite_trajectory, SPRITE_TRAJ_VLC_BITS, 15,

                         &ff_sprite_trajectory_tab[0][1], 4, 2,
                         &ff_sprite_trajectory_tab[0][0], 4, 2, 128);

         INIT_VLC_STATIC(&mb_type_b_vlc, MB_TYPE_B_VLC_BITS, 4,

                         &ff_mb_type_b_tab[0][1], 2, 1,
                         &ff_mb_type_b_tab[0][0], 2, 1, 16);

         done = 1;

     }

 }
 

 int ff_mpeg4_frame_end(AVCodecContext *avctx, const uint8_t *buf, int buf_size)
 {
     Mpeg4DecContext *ctx = avctx->priv_data;
     MpegEncContext    *s = &ctx->m;
 

     /* divx 5.01+ bitstream reorder stuff */
     /* Since this clobbers the input buffer and hwaccel codecs still need the
      * data during hwaccel->end_frame we should not do this any earlier */

     if (s->divx_packed) {

         int current_pos     = s->gb.buffer == s->bitstream_buffer ? 0 : (get_bits_count(&s->gb) >> 3);

         int startcode_found = 0;
 

         if (buf_size - current_pos > 7) {
 

             int i;

             for (i = current_pos; i < buf_size - 4; i++)
 

                 if (buf[i]     == 0 &&
                     buf[i + 1] == 0 &&
                     buf[i + 2] == 1 &&
                     buf[i + 3] == 0xB6) {

                     startcode_found = !(buf[i + 4] & 0x40);

                     break;
                 }
         }
 
         if (startcode_found) {

             if (!ctx->showed_packed_warning) {
                 av_log(s->avctx, AV_LOG_INFO, "Video uses a non-standard and "
                        "wasteful way to store B-frames ('packed B-frames'). "

                        "Consider using the mpeg4_unpack_bframes bitstream filter without encoding but stream copy to fix it.\n");

                 ctx->showed_packed_warning = 1;
             }

             av_fast_padded_malloc(&s->bitstream_buffer,

                            &s->allocated_bitstream_buffer_size,

                            buf_size - current_pos);

             if (!s->bitstream_buffer) {
                 s->bitstream_buffer_size = 0;

                 return AVERROR(ENOMEM);

             }

             memcpy(s->bitstream_buffer, buf + current_pos,
                    buf_size - current_pos);
             s->bitstream_buffer_size = buf_size - current_pos;
         }
     }
 
     return 0;
 }
 

 #if HAVE_THREADS

 static int mpeg4_update_thread_context(AVCodecContext *dst,
                                        const AVCodecContext *src)
 {
     Mpeg4DecContext *s = dst->priv_data;
     const Mpeg4DecContext *s1 = src->priv_data;

     int init = s->m.context_initialized;

 
     int ret = ff_mpeg_update_thread_context(dst, src);
 
     if (ret < 0)
         return ret;
 

     memcpy(((uint8_t*)s) + sizeof(MpegEncContext), ((uint8_t*)s1) + sizeof(MpegEncContext), sizeof(Mpeg4DecContext) - sizeof(MpegEncContext));

     if (CONFIG_MPEG4_DECODER && !init && s1->xvid_build >= 0)

         ff_xvid_idct_init(&s->m.idsp, dst);

     return 0;
 }

 #endif

 static av_cold int init_studio_vlcs(Mpeg4DecContext *ctx)
 {
     int i, ret;
 
     for (i = 0; i < 12; i++) {
         ret = init_vlc(&ctx->studio_intra_tab[i], STUDIO_INTRA_BITS, 22,
                        &ff_mpeg4_studio_intra[i][0][1], 4, 2,
                        &ff_mpeg4_studio_intra[i][0][0], 4, 2,
                        0);
 
         if (ret < 0)
             return ret;
     }
 
     ret = init_vlc(&ctx->studio_luma_dc, STUDIO_INTRA_BITS, 19,
                    &ff_mpeg4_studio_dc_luma[0][1], 4, 2,
                    &ff_mpeg4_studio_dc_luma[0][0], 4, 2,
                    0);
     if (ret < 0)
         return ret;
 
     ret = init_vlc(&ctx->studio_chroma_dc, STUDIO_INTRA_BITS, 19,
                    &ff_mpeg4_studio_dc_chroma[0][1], 4, 2,
                    &ff_mpeg4_studio_dc_chroma[0][0], 4, 2,
                    0);
     if (ret < 0)
         return ret;
 
     return 0;
 }
 

 static av_cold int decode_init(AVCodecContext *avctx)
 {

     Mpeg4DecContext *ctx = avctx->priv_data;
     MpegEncContext *s = &ctx->m;

     int ret;
 

     ctx->divx_version =
     ctx->divx_build   =
     ctx->xvid_build   =
     ctx->lavc_build   = -1;

     if ((ret = ff_h263_decode_init(avctx)) < 0)

         return ret;
 
     ff_mpeg4videodec_static_init();

     if ((ret = init_studio_vlcs(ctx)) < 0)
         return ret;

 
     s->h263_pred = 1;

     s->low_delay = 0; /* default, might be overridden in the vol header during header parsing */

     s->decode_mb = mpeg4_decode_mb;

     ctx->time_increment_bits = 4; /* default value for broken headers */

     avctx->chroma_sample_location = AVCHROMA_LOC_LEFT;

     avctx->internal->allocate_progress = 1;
 

     return 0;
 }
 

 static av_cold int decode_end(AVCodecContext *avctx)
 {
     Mpeg4DecContext *ctx = avctx->priv_data;
     int i;
 

     if (!avctx->internal->is_copy) {
         for (i = 0; i < 12; i++)
             ff_free_vlc(&ctx->studio_intra_tab[i]);

         ff_free_vlc(&ctx->studio_luma_dc);
         ff_free_vlc(&ctx->studio_chroma_dc);
     }

 
     return ff_h263_decode_end(avctx);
 }
 

 static const AVOption mpeg4_options[] = {

     {"quarter_sample", "1/4 subpel MC", offsetof(MpegEncContext, quarter_sample), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, 0},
     {"divx_packed", "divx style packed b frames", offsetof(MpegEncContext, divx_packed), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, 0},

     {NULL}
 };
 
 static const AVClass mpeg4_class = {

     .class_name = "MPEG4 Video Decoder",
     .item_name  = av_default_item_name,
     .option     = mpeg4_options,
     .version    = LIBAVUTIL_VERSION_INT,

 };
 

 AVCodec ff_mpeg4_decoder = {

     .name                  = "mpeg4",

     .long_name             = NULL_IF_CONFIG_SMALL("MPEG-4 part 2"),

     .type                  = AVMEDIA_TYPE_VIDEO,

     .id                    = AV_CODEC_ID_MPEG4,

     .priv_data_size        = sizeof(Mpeg4DecContext),

     .init                  = decode_init,

     .close                 = decode_end,

     .decode                = ff_h263_decode_frame,

     .capabilities          = AV_CODEC_CAP_DRAW_HORIZ_BAND | AV_CODEC_CAP_DR1 |
                              AV_CODEC_CAP_TRUNCATED | AV_CODEC_CAP_DELAY |
                              AV_CODEC_CAP_FRAME_THREADS,

     .caps_internal         = FF_CODEC_CAP_SKIP_FRAME_FILL_PARAM,

     .flush                 = ff_mpeg_flush,

     .max_lowres            = 3,

     .pix_fmts              = ff_h263_hwaccel_pixfmt_list_420,

     .profiles              = NULL_IF_CONFIG_SMALL(ff_mpeg4_video_profiles),

     .update_thread_context = ONLY_IF_THREADS_ENABLED(mpeg4_update_thread_context),

     .priv_class = &mpeg4_class,

     .hw_configs            = (const AVCodecHWConfigInternal*[]) {

 #if CONFIG_MPEG4_NVDEC_HWACCEL

                                HWACCEL_NVDEC(mpeg4),
 #endif
 #if CONFIG_MPEG4_VAAPI_HWACCEL
                                HWACCEL_VAAPI(mpeg4),
 #endif
 #if CONFIG_MPEG4_VDPAU_HWACCEL
                                HWACCEL_VDPAU(mpeg4),
 #endif
 #if CONFIG_MPEG4_VIDEOTOOLBOX_HWACCEL
                                HWACCEL_VIDEOTOOLBOX(mpeg4),
 #endif
                                NULL
                            },

 };