/*
  * ITU H263 bitstream decoder
  * Copyright (c) 2000,2001 Fabrice Bellard
  * H263+ support.
  * Copyright (c) 2001 Juan J. Sierralta P
  * Copyright (c) 2002-2004 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
  */
 
 /**

  * @file

  * h263 decoder.
  */
 

 #define UNCHECKED_BITSTREAM_READER 1

 #include <limits.h>
 

 #include "libavutil/attributes.h"

 #include "libavutil/imgutils.h"

 #include "libavutil/internal.h"

 #include "libavutil/mathematics.h"

 #include "avcodec.h"
 #include "mpegvideo.h"
 #include "h263.h"

 #include "h263data.h"

 #include "internal.h"

 #include "mathops.h"

 #include "mpegutils.h"

 #include "unary.h"
 #include "flv.h"

 #include "rv10.h"

 #include "mpeg4video.h"

 #include "mpegvideodata.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 MV_VLC_BITS 9
 #define H263_MBTYPE_B_VLC_BITS 6
 #define CBPC_B_VLC_BITS 3
 
 static const int h263_mb_type_b_map[15]= {
     MB_TYPE_DIRECT2 | MB_TYPE_L0L1,
     MB_TYPE_DIRECT2 | MB_TYPE_L0L1 | MB_TYPE_CBP,
     MB_TYPE_DIRECT2 | MB_TYPE_L0L1 | MB_TYPE_CBP | MB_TYPE_QUANT,
                       MB_TYPE_L0                                 | MB_TYPE_16x16,
                       MB_TYPE_L0   | MB_TYPE_CBP                 | MB_TYPE_16x16,
                       MB_TYPE_L0   | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
                       MB_TYPE_L1                                 | MB_TYPE_16x16,
                       MB_TYPE_L1   | MB_TYPE_CBP                 | MB_TYPE_16x16,
                       MB_TYPE_L1   | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
                       MB_TYPE_L0L1                               | MB_TYPE_16x16,
                       MB_TYPE_L0L1 | MB_TYPE_CBP                 | MB_TYPE_16x16,
                       MB_TYPE_L0L1 | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
     0, //stuffing
     MB_TYPE_INTRA4x4                | MB_TYPE_CBP,
     MB_TYPE_INTRA4x4                | MB_TYPE_CBP | MB_TYPE_QUANT,
 };
 
 void ff_h263_show_pict_info(MpegEncContext *s){
     if(s->avctx->debug&FF_DEBUG_PICT_INFO){
     av_log(s->avctx, AV_LOG_DEBUG, "qp:%d %c size:%d rnd:%d%s%s%s%s%s%s%s%s%s %d/%d\n",

          s->qscale, av_get_picture_type_char(s->pict_type),

          s->gb.size_in_bits, 1-s->no_rounding,
          s->obmc ? " AP" : "",
          s->umvplus ? " UMV" : "",
          s->h263_long_vectors ? " LONG" : "",
          s->h263_plus ? " +" : "",
          s->h263_aic ? " AIC" : "",
          s->alt_inter_vlc ? " AIV" : "",
          s->modified_quant ? " MQ" : "",
          s->loop_filter ? " LOOP" : "",
          s->h263_slice_structured ? " SS" : "",

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

     );
     }
 }
 
 /***********************************************/
 /* decoding */
 
 VLC ff_h263_intra_MCBPC_vlc;
 VLC ff_h263_inter_MCBPC_vlc;
 VLC ff_h263_cbpy_vlc;
 static VLC mv_vlc;
 static VLC h263_mbtype_b_vlc;
 static VLC cbpc_b_vlc;
 
 /* init vlcs */
 
 /* XXX: find a better solution to handle static init */

 av_cold void ff_h263_decode_init_vlc(void)

 {

     static volatile int done = 0;

 
     if (!done) {
         INIT_VLC_STATIC(&ff_h263_intra_MCBPC_vlc, INTRA_MCBPC_VLC_BITS, 9,
                  ff_h263_intra_MCBPC_bits, 1, 1,
                  ff_h263_intra_MCBPC_code, 1, 1, 72);
         INIT_VLC_STATIC(&ff_h263_inter_MCBPC_vlc, INTER_MCBPC_VLC_BITS, 28,
                  ff_h263_inter_MCBPC_bits, 1, 1,
                  ff_h263_inter_MCBPC_code, 1, 1, 198);
         INIT_VLC_STATIC(&ff_h263_cbpy_vlc, CBPY_VLC_BITS, 16,
                  &ff_h263_cbpy_tab[0][1], 2, 1,
                  &ff_h263_cbpy_tab[0][0], 2, 1, 64);
         INIT_VLC_STATIC(&mv_vlc, MV_VLC_BITS, 33,

                  &ff_mvtab[0][1], 2, 1,
                  &ff_mvtab[0][0], 2, 1, 538);

         ff_rl_init(&ff_h263_rl_inter, ff_h263_static_rl_table_store[0]);
         ff_rl_init(&ff_rl_intra_aic, ff_h263_static_rl_table_store[1]);

         INIT_VLC_RL(ff_h263_rl_inter, 554);

         INIT_VLC_RL(ff_rl_intra_aic, 554);

         INIT_VLC_STATIC(&h263_mbtype_b_vlc, H263_MBTYPE_B_VLC_BITS, 15,

                  &ff_h263_mbtype_b_tab[0][1], 2, 1,
                  &ff_h263_mbtype_b_tab[0][0], 2, 1, 80);

         INIT_VLC_STATIC(&cbpc_b_vlc, CBPC_B_VLC_BITS, 4,

                  &ff_cbpc_b_tab[0][1], 2, 1,
                  &ff_cbpc_b_tab[0][0], 2, 1, 8);

         done = 1;

     }
 }
 
 int ff_h263_decode_mba(MpegEncContext *s)
 {
     int i, mb_pos;
 

     for (i = 0; i < 6; i++)
         if (s->mb_num - 1 <= ff_mba_max[i])
             break;
     mb_pos  = get_bits(&s->gb, ff_mba_length[i]);
     s->mb_x = mb_pos % s->mb_width;
     s->mb_y = mb_pos / s->mb_width;

 
     return mb_pos;
 }
 
 /**

  * Decode the group of blocks header or slice header.

  * @return <0 if an error occurred
  */
 static int h263_decode_gob_header(MpegEncContext *s)
 {

     unsigned int val, gob_number;

     int left;
 
     /* Check for GOB Start Code */
     val = show_bits(&s->gb, 16);
     if(val)
         return -1;
 
         /* We have a GBSC probably with GSTUFF */
     skip_bits(&s->gb, 16); /* Drop the zeros */
     left= get_bits_left(&s->gb);
     //MN: we must check the bits left or we might end in a infinite loop (or segfault)
     for(;left>13; left--){
         if(get_bits1(&s->gb)) break; /* Seek the '1' bit */
     }
     if(left<=13)
         return -1;
 
     if(s->h263_slice_structured){

         if(check_marker(&s->gb, "before MBA")==0)

             return -1;
 
         ff_h263_decode_mba(s);
 
         if(s->mb_num > 1583)

             if(check_marker(&s->gb, "after MBA")==0)

                 return -1;
 
         s->qscale = get_bits(&s->gb, 5); /* SQUANT */

         if(check_marker(&s->gb, "after SQUANT")==0)

             return -1;

         skip_bits(&s->gb, 2); /* GFID */

     }else{
         gob_number = get_bits(&s->gb, 5); /* GN */
         s->mb_x= 0;
         s->mb_y= s->gob_index* gob_number;

         skip_bits(&s->gb, 2); /* GFID */

         s->qscale = get_bits(&s->gb, 5); /* GQUANT */
     }
 
     if(s->mb_y >= s->mb_height)
         return -1;
 
     if(s->qscale==0)
         return -1;
 
     return 0;
 }
 
 /**

  * Decode the group of blocks / video packet header.

  * @return bit position of the resync_marker, or <0 if none was found
  */
 int ff_h263_resync(MpegEncContext *s){
     int left, pos, ret;
 

     if(s->codec_id==AV_CODEC_ID_MPEG4){

         skip_bits1(&s->gb);
         align_get_bits(&s->gb);
     }
 
     if(show_bits(&s->gb, 16)==0){
         pos= get_bits_count(&s->gb);

         if(CONFIG_MPEG4_DECODER && s->codec_id==AV_CODEC_ID_MPEG4)

             ret= ff_mpeg4_decode_video_packet_header(s->avctx->priv_data);

         else
             ret= h263_decode_gob_header(s);
         if(ret>=0)
             return pos;
     }
     //OK, it's not where it is supposed to be ...
     s->gb= s->last_resync_gb;
     align_get_bits(&s->gb);
     left= get_bits_left(&s->gb);
 
     for(;left>16+1+5+5; left-=8){
         if(show_bits(&s->gb, 16)==0){
             GetBitContext bak= s->gb;
 
             pos= get_bits_count(&s->gb);

             if(CONFIG_MPEG4_DECODER && s->codec_id==AV_CODEC_ID_MPEG4)

                 ret= ff_mpeg4_decode_video_packet_header(s->avctx->priv_data);

             else
                 ret= h263_decode_gob_header(s);
             if(ret>=0)
                 return pos;
 
             s->gb= bak;
         }
         skip_bits(&s->gb, 8);
     }
 
     return -1;
 }
 

 int ff_h263_decode_motion(MpegEncContext * s, int pred, int f_code)

 {

     int code, val, sign, shift;

     code = get_vlc2(&s->gb, mv_vlc.table, MV_VLC_BITS, 2);
 
     if (code == 0)
         return pred;
     if (code < 0)
         return 0xffff;
 
     sign = get_bits1(&s->gb);
     shift = f_code - 1;
     val = code;
     if (shift) {
         val = (val - 1) << shift;
         val |= get_bits(&s->gb, shift);
         val++;
     }
     if (sign)
         val = -val;
     val += pred;
 
     /* modulo decoding */
     if (!s->h263_long_vectors) {

         val = sign_extend(val, 5 + f_code);

     } else {
         /* horrible h263 long vector mode */
         if (pred < -31 && val < -63)
             val += 64;
         if (pred > 32 && val > 63)
             val -= 64;
 
     }
     return val;
 }
 
 

 /* Decode RVLC of H.263+ UMV */

 static int h263p_decode_umotion(MpegEncContext * s, int pred)
 {
    int code = 0, sign;
 
    if (get_bits1(&s->gb)) /* Motion difference = 0 */
       return pred;
 
    code = 2 + get_bits1(&s->gb);
 
    while (get_bits1(&s->gb))
    {
       code <<= 1;
       code += get_bits1(&s->gb);
    }
    sign = code & 1;
    code >>= 1;
 
    code = (sign) ? (pred - code) : (pred + code);

    ff_tlog(s->avctx,"H.263+ UMV Motion = %d\n", code);

    return code;
 
 }
 
 /**
  * read the next MVs for OBMC. yes this is a ugly hack, feel free to send a patch :)
  */
 static void preview_obmc(MpegEncContext *s){
     GetBitContext gb= s->gb;
 
     int cbpc, i, pred_x, pred_y, mx, my;
     int16_t *mot_val;
     const int xy= s->mb_x + 1 + s->mb_y * s->mb_stride;
     const int stride= s->b8_stride*2;
 
     for(i=0; i<4; i++)
         s->block_index[i]+= 2;
     for(i=4; i<6; i++)
         s->block_index[i]+= 1;
     s->mb_x++;
 

     av_assert2(s->pict_type == AV_PICTURE_TYPE_P);

 
     do{
         if (get_bits1(&s->gb)) {
             /* skip mb */

             mot_val = s->current_picture.motion_val[0][s->block_index[0]];

             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;
 

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

             goto end;
         }
         cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);
     }while(cbpc == 20);
 
     if(cbpc & 4){

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

     }else{
         get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
         if (cbpc & 8) {
             if(s->modified_quant){
                 if(get_bits1(&s->gb)) skip_bits(&s->gb, 1);
                 else                  skip_bits(&s->gb, 5);
             }else
                 skip_bits(&s->gb, 2);
         }
 
         if ((cbpc & 16) == 0) {

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

                 /* 16x16 motion prediction */

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

                 if (s->umvplus)
                    mx = h263p_decode_umotion(s, pred_x);
                 else

                    mx = ff_h263_decode_motion(s, pred_x, 1);

 
                 if (s->umvplus)
                    my = h263p_decode_umotion(s, pred_y);
                 else

                    my = ff_h263_decode_motion(s, pred_y, 1);

 
                 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 {

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

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

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

                 if (s->umvplus)
                   mx = h263p_decode_umotion(s, pred_x);
                 else

                   mx = ff_h263_decode_motion(s, pred_x, 1);

 
                 if (s->umvplus)
                   my = h263p_decode_umotion(s, pred_y);
                 else

                   my = ff_h263_decode_motion(s, pred_y, 1);

                 if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
                   skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
                 mot_val[0] = mx;
                 mot_val[1] = my;
             }
         }
     }
 end:
 
     for(i=0; i<4; i++)
         s->block_index[i]-= 2;
     for(i=4; i<6; i++)
         s->block_index[i]-= 1;
     s->mb_x--;
 
     s->gb= gb;
 }
 
 static void h263_decode_dquant(MpegEncContext *s){
     static const int8_t quant_tab[4] = { -1, -2, 1, 2 };
 
     if(s->modified_quant){
         if(get_bits1(&s->gb))

             s->qscale= ff_modified_quant_tab[get_bits1(&s->gb)][ s->qscale ];

         else
             s->qscale= get_bits(&s->gb, 5);
     }else
         s->qscale += quant_tab[get_bits(&s->gb, 2)];
     ff_set_qscale(s, s->qscale);
 }
 

 static int h263_decode_block(MpegEncContext * s, int16_t * block,

                              int n, int coded)
 {

     int level, i, j, run;

     RLTable *rl = &ff_h263_rl_inter;
     const uint8_t *scan_table;
     GetBitContext gb= s->gb;
 
     scan_table = s->intra_scantable.permutated;
     if (s->h263_aic && s->mb_intra) {

         rl = &ff_rl_intra_aic;

         i = 0;
         if (s->ac_pred) {
             if (s->h263_aic_dir)
                 scan_table = s->intra_v_scantable.permutated; /* left */
             else
                 scan_table = s->intra_h_scantable.permutated; /* top */
         }
     } else if (s->mb_intra) {
         /* DC coef */

         if (CONFIG_RV10_DECODER && s->codec_id == AV_CODEC_ID_RV10) {

           if (s->rv10_version == 3 && s->pict_type == AV_PICTURE_TYPE_I) {

             int component, diff;
             component = (n <= 3 ? 0 : n - 4 + 1);
             level = s->last_dc[component];
             if (s->rv10_first_dc_coded[component]) {

                 diff = ff_rv_decode_dc(s, n);

                 if (diff == 0xffff)
                     return -1;
                 level += diff;
                 level = level & 0xff; /* handle wrap round */
                 s->last_dc[component] = level;
             } else {
                 s->rv10_first_dc_coded[component] = 1;
             }
           } else {
                 level = get_bits(&s->gb, 8);
                 if (level == 255)
                     level = 128;
           }
         }else{
             level = get_bits(&s->gb, 8);
             if((level&0x7F) == 0){
                 av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);

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

                     return -1;
             }
             if (level == 255)
                 level = 128;
         }
         block[0] = level;
         i = 1;
     } else {
         i = 0;
     }
     if (!coded) {
         if (s->mb_intra && s->h263_aic)
             goto not_coded;
         s->block_last_index[n] = i - 1;
         return 0;
     }
 retry:

     {
     OPEN_READER(re, &s->gb);

     i--; // offset by -1 to allow direct indexing of scan_table

     for(;;) {

         UPDATE_CACHE(re, &s->gb);
         GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);
         if (run == 66) {

             if (level){
                 CLOSE_READER(re, &s->gb);
                 av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
                 return -1;
             }

             /* escape */
             if (CONFIG_FLV_DECODER && s->h263_flv > 1) {

                 int is11 = SHOW_UBITS(re, &s->gb, 1);
                 SKIP_CACHE(re, &s->gb, 1);

                 run = SHOW_UBITS(re, &s->gb, 7) + 1;

                 if (is11) {

                     SKIP_COUNTER(re, &s->gb, 1 + 7);

                     UPDATE_CACHE(re, &s->gb);
                     level = SHOW_SBITS(re, &s->gb, 11);

                     SKIP_COUNTER(re, &s->gb, 11);

                 } else {

                     SKIP_CACHE(re, &s->gb, 7);

                     level = SHOW_SBITS(re, &s->gb, 7);

                     SKIP_COUNTER(re, &s->gb, 1 + 7 + 7);

                 }

             } else {

                 run = SHOW_UBITS(re, &s->gb, 7) + 1;
                 SKIP_CACHE(re, &s->gb, 7);

                 level = (int8_t)SHOW_UBITS(re, &s->gb, 8);

                 SKIP_COUNTER(re, &s->gb, 7 + 8);

                 if(level == -128){

                     UPDATE_CACHE(re, &s->gb);

                     if (s->codec_id == AV_CODEC_ID_RV10) {

                         /* XXX: should patch encoder too */

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

                     }else{

                         level = SHOW_UBITS(re, &s->gb, 5);
                         SKIP_CACHE(re, &s->gb, 5);
                         level |= SHOW_SBITS(re, &s->gb, 6)<<5;
                         SKIP_COUNTER(re, &s->gb, 5 + 6);

                     }
                 }
             }
         } else {

             if (SHOW_UBITS(re, &s->gb, 1))

                 level = -level;

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

         }
         i += run;

         if (i >= 64){

             CLOSE_READER(re, &s->gb);

             // redo update without last flag, revert -1 offset
             i = i - run + ((run-1)&63) + 1;

             if (i < 64) {
                 // only last marker, no overrun
                 block[scan_table[i]] = level;
                 break;
             }

             if(s->alt_inter_vlc && rl == &ff_h263_rl_inter && !s->mb_intra){
                 //Looks like a hack but no, it's the way it is supposed to work ...

                 rl = &ff_rl_intra_aic;

                 i = 0;
                 s->gb= gb;

                 s->bdsp.clear_block(block);

                 goto retry;
             }
             av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d i:%d\n", s->mb_x, s->mb_y, s->mb_intra);
             return -1;
         }

         j = scan_table[i];

         block[j] = level;
     }

     }

 not_coded:
     if (s->mb_intra && s->h263_aic) {

         ff_h263_pred_acdc(s, block, n);

         i = 63;
     }
     s->block_last_index[n] = i;
     return 0;
 }
 
 static int h263_skip_b_part(MpegEncContext *s, int cbp)
 {

     LOCAL_ALIGNED_16(int16_t, dblock, [64]);

     int i, mbi;

     int bli[6];

 
     /* we have to set s->mb_intra to zero to decode B-part of PB-frame correctly
      * but real value should be restored in order to be used later (in OBMC condition)
      */
     mbi = s->mb_intra;

     memcpy(bli, s->block_last_index, sizeof(bli));

     s->mb_intra = 0;
     for (i = 0; i < 6; i++) {
         if (h263_decode_block(s, dblock, i, cbp&32) < 0)
             return -1;
         cbp+=cbp;
     }
     s->mb_intra = mbi;

     memcpy(s->block_last_index, bli, sizeof(bli));

     return 0;
 }
 
 static int h263_get_modb(GetBitContext *gb, int pb_frame, int *cbpb)
 {
     int c, mv = 1;
 
     if (pb_frame < 3) { // h.263 Annex G and i263 PB-frame
         c = get_bits1(gb);
         if (pb_frame == 2 && c)
             mv = !get_bits1(gb);
     } else { // h.263 Annex M improved PB-frame
         mv = get_unary(gb, 0, 4) + 1;
         c = mv & 1;
         mv = !!(mv & 2);
     }
     if(c)
         *cbpb = get_bits(gb, 6);
     return mv;
 }
 
 int ff_h263_decode_mb(MpegEncContext *s,

                       int16_t block[6][64])

 {
     int cbpc, cbpy, i, cbp, pred_x, pred_y, mx, my, dquant;
     int16_t *mot_val;
     const int xy= s->mb_x + s->mb_y * s->mb_stride;
     int cbpb = 0, pb_mv_count = 0;
 

     av_assert2(!s->h263_pred);

     if (s->pict_type == AV_PICTURE_TYPE_P) {

         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;

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

                 s->mv[0][0][0] = 0;
                 s->mv[0][0][1] = 0;
                 s->mb_skipped = !(s->obmc | s->loop_filter);
                 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, "cbpc damaged at %d %d\n", s->mb_x, s->mb_y);
                 return -1;
             }
         }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->pb_frame && get_bits1(&s->gb))
             pb_mv_count = h263_get_modb(&s->gb, s->pb_frame, &cbpb);
         cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
 
         if(s->alt_inter_vlc==0 || (cbpc & 3)!=3)
             cbpy ^= 0xF;
 
         cbp = (cbpc & 3) | (cbpy << 2);
         if (dquant) {
             h263_decode_dquant(s);
         }
 
         s->mv_dir = MV_DIR_FORWARD;
         if ((cbpc & 16) == 0) {

             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);

             if (s->umvplus)
                mx = h263p_decode_umotion(s, pred_x);
             else

                mx = ff_h263_decode_motion(s, pred_x, 1);

 
             if (mx >= 0xffff)
                 return -1;
 
             if (s->umvplus)
                my = h263p_decode_umotion(s, pred_y);
             else

                my = ff_h263_decode_motion(s, pred_y, 1);

 
             if (my >= 0xffff)
                 return -1;
             s->mv[0][0][0] = mx;
             s->mv[0][0][1] = my;
 
             if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
                skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
         } 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);

                 if (s->umvplus)
                   mx = h263p_decode_umotion(s, pred_x);
                 else

                   mx = ff_h263_decode_motion(s, pred_x, 1);

                 if (mx >= 0xffff)
                     return -1;
 
                 if (s->umvplus)
                   my = h263p_decode_umotion(s, pred_y);
                 else

                   my = ff_h263_decode_motion(s, pred_y, 1);

                 if (my >= 0xffff)
                     return -1;
                 s->mv[0][i][0] = mx;
                 s->mv[0][i][1] = my;
                 if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
                   skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
                 mot_val[0] = mx;
                 mot_val[1] = my;
             }
         }

     } else if(s->pict_type==AV_PICTURE_TYPE_B) {

         int mb_type;
         const int stride= s->b8_stride;

         int16_t *mot_val0 = s->current_picture.motion_val[0][2 * (s->mb_x + s->mb_y * stride)];
         int16_t *mot_val1 = s->current_picture.motion_val[1][2 * (s->mb_x + s->mb_y * stride)];

 //        const int mv_xy= s->mb_x + 1 + s->mb_y * s->mb_stride;
 
         //FIXME ugly
         mot_val0[0       ]= mot_val0[2       ]= mot_val0[0+2*stride]= mot_val0[2+2*stride]=
         mot_val0[1       ]= mot_val0[3       ]= mot_val0[1+2*stride]= mot_val0[3+2*stride]=
         mot_val1[0       ]= mot_val1[2       ]= mot_val1[0+2*stride]= mot_val1[2+2*stride]=
         mot_val1[1       ]= mot_val1[3       ]= mot_val1[1+2*stride]= mot_val1[3+2*stride]= 0;
 
         do{
             mb_type= get_vlc2(&s->gb, h263_mbtype_b_vlc.table, H263_MBTYPE_B_VLC_BITS, 2);
             if (mb_type < 0){
                 av_log(s->avctx, AV_LOG_ERROR, "b mb_type damaged at %d %d\n", s->mb_x, s->mb_y);
                 return -1;
             }
 
             mb_type= h263_mb_type_b_map[ mb_type ];
         }while(!mb_type);
 
         s->mb_intra = IS_INTRA(mb_type);
         if(HAS_CBP(mb_type)){

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

             cbpc = get_vlc2(&s->gb, cbpc_b_vlc.table, CBPC_B_VLC_BITS, 1);
             if(s->mb_intra){
                 dquant = IS_QUANT(mb_type);
                 goto 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, "b cbpy damaged at %d %d\n", s->mb_x, s->mb_y);
                 return -1;
             }
 
             if(s->alt_inter_vlc==0 || (cbpc & 3)!=3)
                 cbpy ^= 0xF;
 
             cbp = (cbpc & 3) | (cbpy << 2);
         }else
             cbp=0;
 

         av_assert2(!s->mb_intra);

 
         if(IS_QUANT(mb_type)){
             h263_decode_dquant(s);
         }
 
         if(IS_DIRECT(mb_type)){
             s->mv_dir = MV_DIR_FORWARD | MV_DIR_BACKWARD | MV_DIRECT;
             mb_type |= ff_mpeg4_set_direct_mv(s, 0, 0);
         }else{
             s->mv_dir = 0;
             s->mv_type= MV_TYPE_16X16;
 //FIXME UMV
 
             if(USES_LIST(mb_type, 0)){

                 int16_t *mot_val= ff_h263_pred_motion(s, 0, 0, &mx, &my);

                 s->mv_dir = MV_DIR_FORWARD;
 

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

 
                 s->mv[0][0][0] = mx;
                 s->mv[0][0][1] = my;
                 mot_val[0       ]= mot_val[2       ]= mot_val[0+2*stride]= mot_val[2+2*stride]= mx;
                 mot_val[1       ]= mot_val[3       ]= mot_val[1+2*stride]= mot_val[3+2*stride]= my;
             }
 
             if(USES_LIST(mb_type, 1)){

                 int16_t *mot_val= ff_h263_pred_motion(s, 0, 1, &mx, &my);

                 s->mv_dir |= MV_DIR_BACKWARD;
 

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

 
                 s->mv[1][0][0] = mx;
                 s->mv[1][0][1] = my;
                 mot_val[0       ]= mot_val[2       ]= mot_val[0+2*stride]= mot_val[2+2*stride]= mx;
                 mot_val[1       ]= mot_val[3       ]= mot_val[1+2*stride]= mot_val[3+2*stride]= 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 -1;
             }
         }while(cbpc == 8);
 

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

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

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

         if (s->h263_aic) {
             s->ac_pred = get_bits1(&s->gb);
             if(s->ac_pred){

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

 
                 s->h263_aic_dir = get_bits1(&s->gb);
             }
         }else
             s->ac_pred = 0;
 
         if(s->pb_frame && get_bits1(&s->gb))
             pb_mv_count = h263_get_modb(&s->gb, s->pb_frame, &cbpb);
         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 -1;
         }
         cbp = (cbpc & 3) | (cbpy << 2);
         if (dquant) {
             h263_decode_dquant(s);
         }
 
         pb_mv_count += !!s->pb_frame;
     }
 
     while(pb_mv_count--){

         ff_h263_decode_motion(s, 0, 1);
         ff_h263_decode_motion(s, 0, 1);

     }
 
     /* decode each block */
     for (i = 0; i < 6; i++) {
         if (h263_decode_block(s, block[i], i, cbp&32) < 0)
             return -1;
         cbp+=cbp;
     }
 
     if(s->pb_frame && h263_skip_b_part(s, cbpb) < 0)
         return -1;
     if(s->obmc && !s->mb_intra){

         if(s->pict_type == AV_PICTURE_TYPE_P && s->mb_x+1<s->mb_width && s->mb_num_left != 1)

             preview_obmc(s);
     }
 end:
 
         /* per-MB end of slice check */
     {
         int v= show_bits(&s->gb, 16);
 

         if (get_bits_left(&s->gb) < 16) {
             v >>= 16 - get_bits_left(&s->gb);

         }
 
         if(v==0)
             return SLICE_END;
     }
 
     return SLICE_OK;
 }
 
 /* most is hardcoded. should extend to handle all h263 streams */

 int ff_h263_decode_picture_header(MpegEncContext *s)

 {

     int format, width, height, i, ret;

     uint32_t startcode;
 
     align_get_bits(&s->gb);
 

     if (show_bits(&s->gb, 2) == 2 && s->avctx->frame_number == 0) {
          av_log(s->avctx, AV_LOG_WARNING, "Header looks like RTP instead of H.263\n");
     }
 

     startcode= get_bits(&s->gb, 22-8);
 
     for(i= get_bits_left(&s->gb); i>24; i-=8) {
         startcode = ((startcode << 8) | get_bits(&s->gb, 8)) & 0x003FFFFF;
 
         if(startcode == 0x20)
             break;
     }
 
     if (startcode != 0x20) {
         av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
         return -1;
     }
     /* temporal reference */
     i = get_bits(&s->gb, 8); /* picture timestamp */
     if( (s->picture_number&~0xFF)+i < s->picture_number)
         i+= 256;
     s->picture_number= (s->picture_number&~0xFF) + i;
 
     /* PTYPE starts here */

     if (check_marker(&s->gb, "in PTYPE") != 1) {

         return -1;
     }
     if (get_bits1(&s->gb) != 0) {
         av_log(s->avctx, AV_LOG_ERROR, "Bad H263 id\n");
         return -1;      /* h263 id */
     }
     skip_bits1(&s->gb);         /* split screen off */
     skip_bits1(&s->gb);         /* camera  off */
     skip_bits1(&s->gb);         /* freeze picture release off */
 
     format = get_bits(&s->gb, 3);
     /*
         0    forbidden
         1    sub-QCIF
         10   QCIF
         7       extended PTYPE (PLUSPTYPE)
     */
 
     if (format != 7 && format != 6) {
         s->h263_plus = 0;
         /* H.263v1 */

         width = ff_h263_format[format][0];
         height = ff_h263_format[format][1];

         if (!width)
             return -1;
 

         s->pict_type = AV_PICTURE_TYPE_I + get_bits1(&s->gb);

 
         s->h263_long_vectors = get_bits1(&s->gb);
 
         if (get_bits1(&s->gb) != 0) {
             av_log(s->avctx, AV_LOG_ERROR, "H263 SAC not supported\n");
             return -1; /* SAC: off */
         }
         s->obmc= get_bits1(&s->gb); /* Advanced prediction mode */
         s->unrestricted_mv = s->h263_long_vectors || s->obmc;
 
         s->pb_frame = get_bits1(&s->gb);
         s->chroma_qscale= s->qscale = get_bits(&s->gb, 5);
         skip_bits1(&s->gb); /* Continuous Presence Multipoint mode: off */
 
         s->width = width;
         s->height = height;
         s->avctx->sample_aspect_ratio= (AVRational){12,11};

         s->avctx->framerate = (AVRational){ 30000, 1001 };

     } else {
         int ufep;
 
         /* H.263v2 */
         s->h263_plus = 1;
         ufep = get_bits(&s->gb, 3); /* Update Full Extended PTYPE */
 
         /* ufep other than 0 and 1 are reserved */
         if (ufep == 1) {
             /* OPPTYPE */
             format = get_bits(&s->gb, 3);

             ff_dlog(s->avctx, "ufep=1, format: %d\n", format);

             s->custom_pcf= get_bits1(&s->gb);
             s->umvplus = get_bits1(&s->gb); /* Unrestricted Motion Vector */
             if (get_bits1(&s->gb) != 0) {
                 av_log(s->avctx, AV_LOG_ERROR, "Syntax-based Arithmetic Coding (SAC) not supported\n");
             }
             s->obmc= get_bits1(&s->gb); /* Advanced prediction mode */
             s->h263_aic = get_bits1(&s->gb); /* Advanced Intra Coding (AIC) */
             s->loop_filter= get_bits1(&s->gb);
             s->unrestricted_mv = s->umvplus || s->obmc || s->loop_filter;

             if(s->avctx->lowres)
                 s->loop_filter = 0;

 
             s->h263_slice_structured= get_bits1(&s->gb);
             if (get_bits1(&s->gb) != 0) {
                 av_log(s->avctx, AV_LOG_ERROR, "Reference Picture Selection not supported\n");
             }
             if (get_bits1(&s->gb) != 0) {
                 av_log(s->avctx, AV_LOG_ERROR, "Independent Segment Decoding not supported\n");
             }
             s->alt_inter_vlc= get_bits1(&s->gb);
             s->modified_quant= get_bits1(&s->gb);
             if(s->modified_quant)
                 s->chroma_qscale_table= ff_h263_chroma_qscale_table;
 
             skip_bits(&s->gb, 1); /* Prevent start code emulation */
 
             skip_bits(&s->gb, 3); /* Reserved */
         } else if (ufep != 0) {
             av_log(s->avctx, AV_LOG_ERROR, "Bad UFEP type (%d)\n", ufep);
             return -1;
         }
 
         /* MPPTYPE */
         s->pict_type = get_bits(&s->gb, 3);
         switch(s->pict_type){

         case 0: s->pict_type= AV_PICTURE_TYPE_I;break;
         case 1: s->pict_type= AV_PICTURE_TYPE_P;break;
         case 2: s->pict_type= AV_PICTURE_TYPE_P;s->pb_frame = 3;break;
         case 3: s->pict_type= AV_PICTURE_TYPE_B;break;
         case 7: s->pict_type= AV_PICTURE_TYPE_I;break; //ZYGO

         default:
             return -1;
         }
         skip_bits(&s->gb, 2);
         s->no_rounding = get_bits1(&s->gb);
         skip_bits(&s->gb, 4);
 
         /* Get the picture dimensions */
         if (ufep) {
             if (format == 6) {
                 /* Custom Picture Format (CPFMT) */
                 s->aspect_ratio_info = get_bits(&s->gb, 4);

                 ff_dlog(s->avctx, "aspect: %d\n", s->aspect_ratio_info);

                 /* aspect ratios:
                 0 - forbidden
                 1 - 1:1
                 2 - 12:11 (CIF 4:3)
                 3 - 10:11 (525-type 4:3)
                 4 - 16:11 (CIF 16:9)
                 5 - 40:33 (525-type 16:9)
                 6-14 - reserved
                 */
                 width = (get_bits(&s->gb, 9) + 1) * 4;

                 check_marker(&s->gb, "in dimensions");

                 height = get_bits(&s->gb, 9) * 4;

                 ff_dlog(s->avctx, "\nH.263+ Custom picture: %dx%d\n",width,height);

                 if (s->aspect_ratio_info == FF_ASPECT_EXTENDED) {
                     /* aspected dimensions */
                     s->avctx->sample_aspect_ratio.num= get_bits(&s->gb, 8);
                     s->avctx->sample_aspect_ratio.den= get_bits(&s->gb, 8);
                 }else{
                     s->avctx->sample_aspect_ratio= ff_h263_pixel_aspect[s->aspect_ratio_info];
                 }
             } else {

                 width = ff_h263_format[format][0];
                 height = ff_h263_format[format][1];

                 s->avctx->sample_aspect_ratio= (AVRational){12,11};
             }

             s->avctx->sample_aspect_ratio.den <<= s->ehc_mode;

             if ((width == 0) || (height == 0))
                 return -1;
             s->width = width;
             s->height = height;
 
             if(s->custom_pcf){
                 int gcd;

                 s->avctx->framerate.num  = 1800000;
                 s->avctx->framerate.den  = 1000 + get_bits1(&s->gb);
                 s->avctx->framerate.den *= get_bits(&s->gb, 7);
                 if(s->avctx->framerate.den == 0){

                     av_log(s, AV_LOG_ERROR, "zero framerate\n");
                     return -1;
                 }

                 gcd= av_gcd(s->avctx->framerate.den, s->avctx->framerate.num);
                 s->avctx->framerate.den /= gcd;
                 s->avctx->framerate.num /= gcd;

             }else{

                 s->avctx->framerate = (AVRational){ 30000, 1001 };

             }
         }
 
         if(s->custom_pcf){
             skip_bits(&s->gb, 2); //extended Temporal reference
         }
 
         if (ufep) {
             if (s->umvplus) {
                 if(get_bits1(&s->gb)==0) /* Unlimited Unrestricted Motion Vectors Indicator (UUI) */
                     skip_bits1(&s->gb);
             }
             if(s->h263_slice_structured){
                 if (get_bits1(&s->gb) != 0) {
                     av_log(s->avctx, AV_LOG_ERROR, "rectangular slices not supported\n");
                 }
                 if (get_bits1(&s->gb) != 0) {
                     av_log(s->avctx, AV_LOG_ERROR, "unordered slices not supported\n");
                 }
             }
         }
 
         s->qscale = get_bits(&s->gb, 5);
     }
 

     if ((ret = av_image_check_size(s->width, s->height, 0, s)) < 0)
         return ret;
 

     s->mb_width = (s->width  + 15) / 16;
     s->mb_height = (s->height  + 15) / 16;
     s->mb_num = s->mb_width * s->mb_height;
 
     if (s->pb_frame) {
         skip_bits(&s->gb, 3); /* Temporal reference for B-pictures */
         if (s->custom_pcf)
             skip_bits(&s->gb, 2); //extended Temporal reference
         skip_bits(&s->gb, 2); /* Quantization information for B-pictures */
     }
 

     if (s->pict_type!=AV_PICTURE_TYPE_B) {

         s->time            = s->picture_number;
         s->pp_time         = s->time - s->last_non_b_time;
         s->last_non_b_time = s->time;

     }else{

         s->time    = s->picture_number;
         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){

             s->pp_time = 2;
             s->pb_time = 1;
         }
         ff_mpeg4_init_direct_mv(s);
     }
 

     /* PEI */

     if (skip_1stop_8data_bits(&s->gb) < 0)
         return AVERROR_INVALIDDATA;

 
     if(s->h263_slice_structured){

         if (check_marker(&s->gb, "SEPB1") != 1) {

             return -1;
         }
 
         ff_h263_decode_mba(s);
 

         if (check_marker(&s->gb, "SEPB2") != 1) {

             return -1;
         }
     }
     s->f_code = 1;
 
     if(s->h263_aic){
          s->y_dc_scale_table=
          s->c_dc_scale_table= ff_aic_dc_scale_table;
     }else{
         s->y_dc_scale_table=
         s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
     }
 
         ff_h263_show_pict_info(s);

     if (s->pict_type == AV_PICTURE_TYPE_I && s->codec_tag == AV_RL32("ZYGO") && get_bits_left(&s->gb) >= 85 + 13*3*16 + 50){

         int i,j;
         for(i=0; i<85; i++) av_log(s->avctx, AV_LOG_DEBUG, "%d", get_bits1(&s->gb));
         av_log(s->avctx, AV_LOG_DEBUG, "\n");
         for(i=0; i<13; i++){
             for(j=0; j<3; j++){
                 int v= get_bits(&s->gb, 8);
                 v |= get_sbits(&s->gb, 8)<<8;
                 av_log(s->avctx, AV_LOG_DEBUG, " %5d", v);
             }
             av_log(s->avctx, AV_LOG_DEBUG, "\n");
         }
         for(i=0; i<50; i++) av_log(s->avctx, AV_LOG_DEBUG, "%d", get_bits1(&s->gb));
     }
 
     return 0;
 }