/*
  * Microsoft Screen 4 (aka Microsoft Expression Encoder Screen) decoder
  * Copyright (c) 2012 Konstantin Shishkov
  *

  * 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
  * Microsoft Screen 4 (aka Microsoft Titanium Screen 2,
  * aka Microsoft Expression Encoder Screen) decoder
  */
 
 #include "avcodec.h"
 #include "bytestream.h"
 #include "get_bits.h"

 #include "internal.h"

 #include "mss34dsp.h"
 #include "unary.h"
 
 #define HEADER_SIZE 8
 
 enum FrameType {
     INTRA_FRAME = 0,
     INTER_FRAME,
     SKIP_FRAME
 };
 
 enum BlockType {
     SKIP_BLOCK = 0,
     DCT_BLOCK,
     IMAGE_BLOCK,
 };
 
 enum CachePos {
     LEFT = 0,
     TOP_LEFT,
     TOP,
 };
 
 static const uint8_t mss4_dc_vlc_lens[2][16] = {
     { 0, 1, 5, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0 },
     { 0, 3, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0 }
 };
 
 static const uint8_t mss4_ac_vlc_lens[2][16] = {
     { 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 125 },
     { 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 119 }
 };
 
 static const uint8_t mss4_ac_vlc_syms[2][162] = {
   { 0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,
     0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
     0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xA1, 0x08,
     0x23, 0x42, 0xB1, 0xC1, 0x15, 0x52, 0xD1, 0xF0,
     0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0A, 0x16,
     0x17, 0x18, 0x19, 0x1A, 0x25, 0x26, 0x27, 0x28,
     0x29, 0x2A, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
     0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
     0x4A, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
     0x5A, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
     0x6A, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
     0x7A, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
     0x8A, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,
     0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7,
     0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6,
     0xB7, 0xB8, 0xB9, 0xBA, 0xC2, 0xC3, 0xC4, 0xC5,
     0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xD2, 0xD3, 0xD4,
     0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xE1, 0xE2,
     0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA,
     0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8,
     0xF9, 0xFA  },
   { 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,
     0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,
     0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,
     0xA1, 0xB1, 0xC1, 0x09, 0x23, 0x33, 0x52, 0xF0,
     0x15, 0x62, 0x72, 0xD1, 0x0A, 0x16, 0x24, 0x34,
     0xE1, 0x25, 0xF1, 0x17, 0x18, 0x19, 0x1A, 0x26,
     0x27, 0x28, 0x29, 0x2A, 0x35, 0x36, 0x37, 0x38,
     0x39, 0x3A, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
     0x49, 0x4A, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
     0x59, 0x5A, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
     0x69, 0x6A, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
     0x79, 0x7A, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
     0x88, 0x89, 0x8A, 0x92, 0x93, 0x94, 0x95, 0x96,
     0x97, 0x98, 0x99, 0x9A, 0xA2, 0xA3, 0xA4, 0xA5,
     0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xB2, 0xB3, 0xB4,
     0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xC2, 0xC3,
     0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xD2,
     0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA,
     0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9,
     0xEA, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8,
     0xF9, 0xFA  }
 };
 
 static const uint8_t vec_len_syms[2][4] = {
     { 4, 2, 3, 1 },
     { 4, 1, 2, 3 }
 };
 
 static const uint8_t mss4_vec_entry_vlc_lens[2][16] = {
     { 0, 2, 2, 3, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 },
     { 0, 1, 5, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }
 };
 
 static const uint8_t mss4_vec_entry_vlc_syms[2][9] = {
     { 0, 7, 6, 5, 8, 4, 3, 1, 2 },
     { 0, 2, 3, 4, 5, 6, 7, 1, 8 }
 };
 
 #define MAX_ENTRIES  162
 
 typedef struct MSS4Context {

     AVFrame    *pic;

 
     VLC        dc_vlc[2], ac_vlc[2];
     VLC        vec_entry_vlc[2];
     int        block[64];
     uint8_t    imgbuf[3][16 * 16];
 
     int        quality;
     uint16_t   quant_mat[2][64];
 
     int        *prev_dc[3];

     ptrdiff_t  dc_stride[3];

     int        dc_cache[4][4];
 
     int        prev_vec[3][4];
 } MSS4Context;
 
 static av_cold int mss4_init_vlc(VLC *vlc, const uint8_t *lens,
                                  const uint8_t *syms, int num_syms)
 {
     uint8_t  bits[MAX_ENTRIES];
     uint16_t codes[MAX_ENTRIES];
     int i, j;
     int prefix = 0, max_bits = 0, idx = 0;
 
     for (i = 0; i < 16; i++) {
         for (j = 0; j < lens[i]; j++) {
             bits[idx]  = i + 1;
             codes[idx] = prefix++;
             max_bits   = i + 1;
             idx++;
         }
         prefix <<= 1;
     }
 
     return ff_init_vlc_sparse(vlc, FFMIN(max_bits, 9), num_syms, bits, 1, 1,
                               codes, 2, 2, syms, 1, 1, 0);
 }
 
 static av_cold int mss4_init_vlcs(MSS4Context *ctx)
 {
     int ret, i;
 
     for (i = 0; i < 2; i++) {
         ret = mss4_init_vlc(&ctx->dc_vlc[i], mss4_dc_vlc_lens[i], NULL, 12);
         if (ret)
             return ret;
         ret = mss4_init_vlc(&ctx->ac_vlc[i], mss4_ac_vlc_lens[i],
                             mss4_ac_vlc_syms[i], 162);
         if (ret)
             return ret;
         ret = mss4_init_vlc(&ctx->vec_entry_vlc[i], mss4_vec_entry_vlc_lens[i],
                             mss4_vec_entry_vlc_syms[i], 9);
         if (ret)
             return ret;
     }
     return 0;
 }
 
 static av_cold void mss4_free_vlcs(MSS4Context *ctx)
 {
     int i;
 
     for (i = 0; i < 2; i++) {
         ff_free_vlc(&ctx->dc_vlc[i]);
         ff_free_vlc(&ctx->ac_vlc[i]);
         ff_free_vlc(&ctx->vec_entry_vlc[i]);
     }
 }
 
 /* This function returns values in the range
  * (-range + 1; -range/2] U [range/2; range - 1)
  * i.e.
  * nbits = 0 -> 0
  * nbits = 1 -> -1, 1
  * nbits = 2 -> -3, -2, 2, 3
  */
 static av_always_inline int get_coeff_bits(GetBitContext *gb, int nbits)
 {
     int val;
 
     if (!nbits)
         return 0;
 
     val = get_bits(gb, nbits);
     if (val < (1 << (nbits - 1)))
         val -= (1 << nbits) - 1;
 
     return val;
 }
 
 static inline int get_coeff(GetBitContext *gb, VLC *vlc)
 {
     int val = get_vlc2(gb, vlc->table, vlc->bits, 2);
 
     return get_coeff_bits(gb, val);
 }
 
 static int mss4_decode_dct(GetBitContext *gb, VLC *dc_vlc, VLC *ac_vlc,
                            int *block, int *dc_cache,
                            int bx, int by, uint16_t *quant_mat)
 {
     int skip, val, pos = 1, zz_pos, dc;
 
     memset(block, 0, sizeof(*block) * 64);
 
     dc = get_coeff(gb, dc_vlc);
     // DC prediction is the same as in MSS3
     if (by) {
         if (bx) {
             int l, tl, t;
 
             l  = dc_cache[LEFT];
             tl = dc_cache[TOP_LEFT];
             t  = dc_cache[TOP];
 
             if (FFABS(t - tl) <= FFABS(l - tl))
                 dc += l;
             else
                 dc += t;
         } else {
             dc += dc_cache[TOP];
         }
     } else if (bx) {
         dc += dc_cache[LEFT];
     }
     dc_cache[LEFT] = dc;
     block[0]       = dc * quant_mat[0];
 
     while (pos < 64) {
         val = get_vlc2(gb, ac_vlc->table, 9, 2);
         if (!val)
             return 0;
         if (val == -1)
             return -1;
         if (val == 0xF0) {
             pos += 16;
             continue;
         }
         skip = val >> 4;
         val  = get_coeff_bits(gb, val & 0xF);
         pos += skip;
         if (pos >= 64)
             return -1;
 
         zz_pos = ff_zigzag_direct[pos];
         block[zz_pos] = val * quant_mat[zz_pos];
         pos++;
     }
 
     return pos == 64 ? 0 : -1;
 }
 
 static int mss4_decode_dct_block(MSS4Context *c, GetBitContext *gb,
                                  uint8_t *dst[3], int mb_x, int mb_y)
 {
     int i, j, k, ret;
     uint8_t *out = dst[0];
 
     for (j = 0; j < 2; j++) {
         for (i = 0; i < 2; i++) {
             int xpos = mb_x * 2 + i;
             c->dc_cache[j][TOP_LEFT] = c->dc_cache[j][TOP];
             c->dc_cache[j][TOP]      = c->prev_dc[0][mb_x * 2 + i];
             ret = mss4_decode_dct(gb, c->dc_vlc, c->ac_vlc, c->block,
                                   c->dc_cache[j],
                                   xpos, mb_y * 2 + j, c->quant_mat[0]);
             if (ret)
                 return ret;
             c->prev_dc[0][mb_x * 2 + i] = c->dc_cache[j][LEFT];
 

             ff_mss34_dct_put(out + xpos * 8, c->pic->linesize[0],

                              c->block);
         }

         out += 8 * c->pic->linesize[0];

     }
 
     for (i = 1; i < 3; i++) {
         c->dc_cache[i + 1][TOP_LEFT] = c->dc_cache[i + 1][TOP];
         c->dc_cache[i + 1][TOP]      = c->prev_dc[i][mb_x];
         ret = mss4_decode_dct(gb, c->dc_vlc + 1, c->ac_vlc + 1,
                               c->block, c->dc_cache[i + 1], mb_x, mb_y,
                               c->quant_mat[1]);
         if (ret)
             return ret;
         c->prev_dc[i][mb_x] = c->dc_cache[i + 1][LEFT];
 
         ff_mss34_dct_put(c->imgbuf[i], 8, c->block);
         out = dst[i] + mb_x * 16;
         // Since the DCT block is coded as YUV420 and the whole frame as YUV444,
         // we need to scale chroma.
         for (j = 0; j < 16; j++) {
             for (k = 0; k < 8; k++)
                 AV_WN16A(out + k * 2, c->imgbuf[i][k + (j & ~1) * 4] * 0x101);

             out += c->pic->linesize[i];

         }
     }
 
     return 0;
 }
 
 static void read_vec_pos(GetBitContext *gb, int *vec_pos, int *sel_flag,
                          int *sel_len, int *prev)
 {
     int i, y_flag = 0;
 
     for (i = 2; i >= 0; i--) {
         if (!sel_flag[i]) {
             vec_pos[i] = 0;
             continue;
         }
         if ((!i && !y_flag) || get_bits1(gb)) {
             if (sel_len[i] > 0) {
                 int pval = prev[i];
                 vec_pos[i] = get_bits(gb, sel_len[i]);
                 if (vec_pos[i] >= pval)
                     vec_pos[i]++;
             } else {
                 vec_pos[i] = !prev[i];
             }
             y_flag = 1;
         } else {
             vec_pos[i] = prev[i];
         }
     }
 }
 
 static int get_value_cached(GetBitContext *gb, int vec_pos, uint8_t *vec,
                             int vec_size, int component, int shift, int *prev)
 {
     if (vec_pos < vec_size)
         return vec[vec_pos];
     if (!get_bits1(gb))
         return prev[component];
     prev[component] = get_bits(gb, 8 - shift) << shift;
     return prev[component];
 }
 

 #define MKVAL(vals)  ((vals)[0] | ((vals)[1] << 3) | ((vals)[2] << 6))

 
 /* Image mode - the hardest to comprehend MSS4 coding mode.
  *
  * In this mode all three 16x16 blocks are coded together with a method
  * remotely similar to the methods employed in MSS1-MSS3.
  * The idea is that every component has a vector of 1-4 most common symbols
  * and an escape mode for reading new value from the bitstream. Decoding
  * consists of retrieving pixel values from the vector or reading new ones
  * from the bitstream; depending on flags read from the bitstream, these vector
  * positions can be updated or reused from the state of the previous line
  * or previous pixel.
  */
 static int mss4_decode_image_block(MSS4Context *ctx, GetBitContext *gb,
                                    uint8_t *picdst[3], int mb_x, int mb_y)
 {
     uint8_t vec[3][4];
     int     vec_len[3];
     int     sel_len[3], sel_flag[3];
     int     i, j, k, mode, split;
     int     prev_vec1 = 0, prev_split = 0;
     int     vals[3] = { 0 };
     int     prev_pix[3] = { 0 };
     int     prev_mode[16] = { 0 };
     uint8_t *dst[3];
 
     const int val_shift = ctx->quality == 100 ? 0 : 2;
 
     for (i = 0; i < 3; i++)
         dst[i] = ctx->imgbuf[i];
 
     for (i = 0; i < 3; i++) {
         vec_len[i] = vec_len_syms[!!i][get_unary(gb, 0, 3)];
         for (j = 0; j < vec_len[i]; j++) {
             vec[i][j]  = get_coeff(gb, &ctx->vec_entry_vlc[!!i]);
             vec[i][j] += ctx->prev_vec[i][j];
             ctx->prev_vec[i][j] = vec[i][j];
         }
         sel_flag[i] = vec_len[i] > 1;
         sel_len[i]  = vec_len[i] > 2 ? vec_len[i] - 2 : 0;
     }
 
     for (j = 0; j < 16; j++) {
         if (get_bits1(gb)) {
             split = 0;
             if (get_bits1(gb)) {
                 prev_mode[0] = 0;
                 vals[0] = vals[1] = vals[2] = 0;
                 mode = 2;
             } else {
                 mode = get_bits1(gb);
                 if (mode)
                     split = get_bits(gb, 4);
             }
             for (i = 0; i < 16; i++) {
                 if (mode <= 1) {
                     vals[0] =  prev_mode[i]       & 7;
                     vals[1] = (prev_mode[i] >> 3) & 7;
                     vals[2] =  prev_mode[i] >> 6;
                     if (mode == 1 && i == split) {
                         read_vec_pos(gb, vals, sel_flag, sel_len, vals);
                     }
                 } else if (mode == 2) {
                     if (get_bits1(gb))
                         read_vec_pos(gb, vals, sel_flag, sel_len, vals);
                 }
                 for (k = 0; k < 3; k++)
                     *dst[k]++ = get_value_cached(gb, vals[k], vec[k],
                                                  vec_len[k], k,
                                                  val_shift, prev_pix);
                 prev_mode[i] = MKVAL(vals);
             }
         } else {
             if (get_bits1(gb)) {
                 split = get_bits(gb, 4);
                 if (split >= prev_split)
                     split++;
                 prev_split = split;
             } else {
                 split = prev_split;
             }
             if (split) {
                 vals[0] =  prev_mode[0]       & 7;
                 vals[1] = (prev_mode[0] >> 3) & 7;
                 vals[2] =  prev_mode[0] >> 6;
                 for (i = 0; i < 3; i++) {
                     for (k = 0; k < split; k++) {
                         *dst[i]++ = get_value_cached(gb, vals[i], vec[i],
                                                      vec_len[i], i, val_shift,
                                                      prev_pix);
                         prev_mode[k] = MKVAL(vals);
                     }
                 }
             }
 
             if (split != 16) {
                 vals[0] =  prev_vec1       & 7;
                 vals[1] = (prev_vec1 >> 3) & 7;
                 vals[2] =  prev_vec1 >> 6;
                 if (get_bits1(gb)) {
                     read_vec_pos(gb, vals, sel_flag, sel_len, vals);
                     prev_vec1 = MKVAL(vals);
                 }
                 for (i = 0; i < 3; i++) {
                     for (k = 0; k < 16 - split; k++) {
                         *dst[i]++ = get_value_cached(gb, vals[i], vec[i],
                                                      vec_len[i], i, val_shift,
                                                      prev_pix);
                         prev_mode[split + k] = MKVAL(vals);
                     }
                 }
             }
         }
     }
 
     for (i = 0; i < 3; i++)
         for (j = 0; j < 16; j++)

             memcpy(picdst[i] + mb_x * 16 + j * ctx->pic->linesize[i],

                    ctx->imgbuf[i] + j * 16, 16);
 
     return 0;
 }
 
 static inline void mss4_update_dc_cache(MSS4Context *c, int mb_x)
 {
     int i;
 
     c->dc_cache[0][TOP]  = c->prev_dc[0][mb_x * 2 + 1];
     c->dc_cache[0][LEFT] = 0;
     c->dc_cache[1][TOP]  = 0;
     c->dc_cache[1][LEFT] = 0;
 
     for (i = 0; i < 2; i++)
         c->prev_dc[0][mb_x * 2 + i] = 0;
 
     for (i = 1; i < 3; i++) {
         c->dc_cache[i + 1][TOP]  = c->prev_dc[i][mb_x];
         c->dc_cache[i + 1][LEFT] = 0;
         c->prev_dc[i][mb_x]      = 0;
     }
 }
 

 static int mss4_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,

                              AVPacket *avpkt)
 {
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     MSS4Context *c = avctx->priv_data;
     GetBitContext gb;
     GetByteContext bc;
     uint8_t *dst[3];
     int width, height, quality, frame_type;
     int x, y, i, mb_width, mb_height, blk_type;
     int ret;
 
     if (buf_size < HEADER_SIZE) {
         av_log(avctx, AV_LOG_ERROR,
                "Frame should have at least %d bytes, got %d instead\n",
                HEADER_SIZE, buf_size);
         return AVERROR_INVALIDDATA;
     }
 
     bytestream2_init(&bc, buf, buf_size);
     width      = bytestream2_get_be16(&bc);
     height     = bytestream2_get_be16(&bc);
     bytestream2_skip(&bc, 2);
     quality    = bytestream2_get_byte(&bc);
     frame_type = bytestream2_get_byte(&bc);
 
     if (width > avctx->width ||
         height != avctx->height) {
         av_log(avctx, AV_LOG_ERROR, "Invalid frame dimensions %dx%d\n",
                width, height);
         return AVERROR_INVALIDDATA;
     }
     if (quality < 1 || quality > 100) {
         av_log(avctx, AV_LOG_ERROR, "Invalid quality setting %d\n", quality);
         return AVERROR_INVALIDDATA;
     }
     if ((frame_type & ~3) || frame_type == 3) {
         av_log(avctx, AV_LOG_ERROR, "Invalid frame type %d\n", frame_type);
         return AVERROR_INVALIDDATA;
     }
 
     if (frame_type != SKIP_FRAME && !bytestream2_get_bytes_left(&bc)) {
         av_log(avctx, AV_LOG_ERROR,
                "Empty frame found but it is not a skip frame.\n");
         return AVERROR_INVALIDDATA;
     }
 

     if ((ret = ff_reget_buffer(avctx, c->pic)) < 0)

         return ret;

     c->pic->key_frame = (frame_type == INTRA_FRAME);
     c->pic->pict_type = (frame_type == INTRA_FRAME) ? AV_PICTURE_TYPE_I

                                                    : AV_PICTURE_TYPE_P;
     if (frame_type == SKIP_FRAME) {

         *got_frame      = 1;

         if ((ret = av_frame_ref(data, c->pic)) < 0)

             return ret;

 
         return buf_size;
     }
 
     if (c->quality != quality) {
         c->quality = quality;
         for (i = 0; i < 2; i++)
             ff_mss34_gen_quant_mat(c->quant_mat[i], quality, !i);
     }
 

     if ((ret = init_get_bits8(&gb, buf + HEADER_SIZE, buf_size - HEADER_SIZE)) < 0)
         return ret;

 
     mb_width  = FFALIGN(width,  16) >> 4;
     mb_height = FFALIGN(height, 16) >> 4;

     dst[0] = c->pic->data[0];
     dst[1] = c->pic->data[1];
     dst[2] = c->pic->data[2];

 
     memset(c->prev_vec, 0, sizeof(c->prev_vec));
     for (y = 0; y < mb_height; y++) {
         memset(c->dc_cache, 0, sizeof(c->dc_cache));
         for (x = 0; x < mb_width; x++) {
             blk_type = decode012(&gb);
             switch (blk_type) {
             case DCT_BLOCK:
                 if (mss4_decode_dct_block(c, &gb, dst, x, y) < 0) {
                     av_log(avctx, AV_LOG_ERROR,
                            "Error decoding DCT block %d,%d\n",
                            x, y);
                     return AVERROR_INVALIDDATA;
                 }
                 break;
             case IMAGE_BLOCK:
                 if (mss4_decode_image_block(c, &gb, dst, x, y) < 0) {
                     av_log(avctx, AV_LOG_ERROR,
                            "Error decoding VQ block %d,%d\n",
                            x, y);
                     return AVERROR_INVALIDDATA;
                 }
                 break;
             case SKIP_BLOCK:
                 if (frame_type == INTRA_FRAME) {
                     av_log(avctx, AV_LOG_ERROR, "Skip block in intra frame\n");
                     return AVERROR_INVALIDDATA;
                 }
                 break;
             }
             if (blk_type != DCT_BLOCK)
                 mss4_update_dc_cache(c, x);
         }

         dst[0] += c->pic->linesize[0] * 16;
         dst[1] += c->pic->linesize[1] * 16;
         dst[2] += c->pic->linesize[2] * 16;

     }
 

     if ((ret = av_frame_ref(data, c->pic)) < 0)

         return ret;
 

     *got_frame      = 1;

 
     return buf_size;
 }
 

 static av_cold int mss4_decode_end(AVCodecContext *avctx)

 {
     MSS4Context * const c = avctx->priv_data;
     int i;
 

     av_frame_free(&c->pic);
     for (i = 0; i < 3; i++)
         av_freep(&c->prev_dc[i]);
     mss4_free_vlcs(c);
 
     return 0;
 }
 

 static av_cold int mss4_decode_init(AVCodecContext *avctx)
 {
     MSS4Context * const c = avctx->priv_data;
     int i;

     if (mss4_init_vlcs(c)) {
         av_log(avctx, AV_LOG_ERROR, "Cannot initialise VLCs\n");
         mss4_free_vlcs(c);
         return AVERROR(ENOMEM);
     }
     for (i = 0; i < 3; i++) {
         c->dc_stride[i] = FFALIGN(avctx->width, 16) >> (2 + !!i);

         c->prev_dc[i]   = av_malloc_array(c->dc_stride[i], sizeof(**c->prev_dc));

         if (!c->prev_dc[i]) {
             av_log(avctx, AV_LOG_ERROR, "Cannot allocate buffer\n");
             mss4_free_vlcs(c);
             return AVERROR(ENOMEM);
         }
     }
 

     c->pic = av_frame_alloc();
     if (!c->pic) {
         mss4_decode_end(avctx);
         return AVERROR(ENOMEM);
     }

     avctx->pix_fmt     = AV_PIX_FMT_YUV444P;

 
     return 0;
 }
 
 AVCodec ff_mts2_decoder = {
     .name           = "mts2",

     .long_name      = NULL_IF_CONFIG_SMALL("MS Expression Encoder Screen"),

     .type           = AVMEDIA_TYPE_VIDEO,

     .id             = AV_CODEC_ID_MTS2,

     .priv_data_size = sizeof(MSS4Context),
     .init           = mss4_decode_init,
     .close          = mss4_decode_end,
     .decode         = mss4_decode_frame,

     .capabilities   = AV_CODEC_CAP_DR1,

 };