/*
  * Microsoft Screen 3 (aka Microsoft ATC 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 3 (aka Microsoft ATC Screen) decoder
  */
 
 #include "avcodec.h"
 #include "bytestream.h"

 #include "dsputil.h"

 #include "internal.h"

 #include "mss34dsp.h"

 
 #define HEADER_SIZE 27
 
 #define MODEL2_SCALE       13
 #define MODEL_SCALE        15
 #define MODEL256_SEC_SCALE  9
 
 typedef struct Model2 {
     int      upd_val, till_rescale;
     unsigned zero_freq,  zero_weight;
     unsigned total_freq, total_weight;
 } Model2;
 
 typedef struct Model {
     int weights[16], freqs[16];
     int num_syms;
     int tot_weight;
     int upd_val, max_upd_val, till_rescale;
 } Model;
 
 typedef struct Model256 {
     int weights[256], freqs[256];
     int tot_weight;
     int secondary[68];
     int sec_size;
     int upd_val, max_upd_val, till_rescale;
 } Model256;
 
 #define RAC_BOTTOM 0x01000000
 typedef struct RangeCoder {
     const uint8_t *src, *src_end;
 
     uint32_t range, low;
     int got_error;
 } RangeCoder;
 
 enum BlockType {
     FILL_BLOCK = 0,
     IMAGE_BLOCK,
     DCT_BLOCK,
     HAAR_BLOCK,
     SKIP_BLOCK
 };
 
 typedef struct BlockTypeContext {
     int      last_type;
     Model    bt_model[5];
 } BlockTypeContext;
 
 typedef struct FillBlockCoder {
     int      fill_val;
     Model    coef_model;
 } FillBlockCoder;
 
 typedef struct ImageBlockCoder {
     Model256 esc_model, vec_entry_model;
     Model    vec_size_model;
     Model    vq_model[125];
 } ImageBlockCoder;
 
 typedef struct DCTBlockCoder {
     int      *prev_dc;
     int      prev_dc_stride;
     int      prev_dc_height;
     int      quality;
     uint16_t qmat[64];
     Model    dc_model;
     Model2   sign_model;
     Model256 ac_model;
 } DCTBlockCoder;
 
 typedef struct HaarBlockCoder {
     int      quality, scale;
     Model256 coef_model;
     Model    coef_hi_model;
 } HaarBlockCoder;
 
 typedef struct MSS3Context {
     AVCodecContext   *avctx;

     AVFrame          *pic;

 
     int              got_error;
     RangeCoder       coder;
     BlockTypeContext btype[3];
     FillBlockCoder   fill_coder[3];
     ImageBlockCoder  image_coder[3];
     DCTBlockCoder    dct_coder[3];
     HaarBlockCoder   haar_coder[3];
 
     int              dctblock[64];
     int              hblock[16 * 16];
 } MSS3Context;
 
 
 static void model2_reset(Model2 *m)
 {
     m->zero_weight  = 1;
     m->total_weight = 2;
     m->zero_freq    = 0x1000;
     m->total_freq   = 0x2000;
     m->upd_val      = 4;
     m->till_rescale = 4;
 }
 
 static void model2_update(Model2 *m, int bit)
 {
     unsigned scale;
 
     if (!bit)
         m->zero_weight++;
     m->till_rescale--;
     if (m->till_rescale)
         return;
 
     m->total_weight += m->upd_val;
     if (m->total_weight > 0x2000) {
         m->total_weight = (m->total_weight + 1) >> 1;
         m->zero_weight  = (m->zero_weight  + 1) >> 1;
         if (m->total_weight == m->zero_weight)
             m->total_weight = m->zero_weight + 1;
     }
     m->upd_val = m->upd_val * 5 >> 2;
     if (m->upd_val > 64)
         m->upd_val = 64;
     scale = 0x80000000u / m->total_weight;
     m->zero_freq    = m->zero_weight  * scale >> 18;
     m->total_freq   = m->total_weight * scale >> 18;
     m->till_rescale = m->upd_val;
 }
 
 static void model_update(Model *m, int val)
 {
     int i, sum = 0;
     unsigned scale;
 
     m->weights[val]++;
     m->till_rescale--;
     if (m->till_rescale)
         return;
     m->tot_weight += m->upd_val;
 
     if (m->tot_weight > 0x8000) {
         m->tot_weight = 0;
         for (i = 0; i < m->num_syms; i++) {
             m->weights[i]  = (m->weights[i] + 1) >> 1;
             m->tot_weight +=  m->weights[i];
         }
     }
     scale = 0x80000000u / m->tot_weight;
     for (i = 0; i < m->num_syms; i++) {
         m->freqs[i] = sum * scale >> 16;
         sum += m->weights[i];
     }
 
     m->upd_val = m->upd_val * 5 >> 2;
     if (m->upd_val > m->max_upd_val)
         m->upd_val = m->max_upd_val;
     m->till_rescale = m->upd_val;
 }
 
 static void model_reset(Model *m)
 {
     int i;
 
     m->tot_weight   = 0;
     for (i = 0; i < m->num_syms - 1; i++)
         m->weights[i] = 1;
     m->weights[m->num_syms - 1] = 0;
 
     m->upd_val      = m->num_syms;
     m->till_rescale = 1;
     model_update(m, m->num_syms - 1);
     m->till_rescale =
     m->upd_val      = (m->num_syms + 6) >> 1;
 }
 
 static av_cold void model_init(Model *m, int num_syms)
 {
     m->num_syms    = num_syms;
     m->max_upd_val = 8 * num_syms + 48;
 
     model_reset(m);
 }
 
 static void model256_update(Model256 *m, int val)
 {
     int i, sum = 0;
     unsigned scale;
     int send, sidx = 1;
 
     m->weights[val]++;
     m->till_rescale--;
     if (m->till_rescale)
         return;
     m->tot_weight += m->upd_val;
 
     if (m->tot_weight > 0x8000) {
         m->tot_weight = 0;
         for (i = 0; i < 256; i++) {
             m->weights[i]  = (m->weights[i] + 1) >> 1;
             m->tot_weight +=  m->weights[i];
         }
     }
     scale = 0x80000000u / m->tot_weight;
     m->secondary[0] = 0;
     for (i = 0; i < 256; i++) {
         m->freqs[i] = sum * scale >> 16;
         sum += m->weights[i];
         send = m->freqs[i] >> MODEL256_SEC_SCALE;
         while (sidx <= send)
             m->secondary[sidx++] = i - 1;
     }
     while (sidx < m->sec_size)
         m->secondary[sidx++] = 255;
 
     m->upd_val = m->upd_val * 5 >> 2;
     if (m->upd_val > m->max_upd_val)
         m->upd_val = m->max_upd_val;
     m->till_rescale = m->upd_val;
 }
 
 static void model256_reset(Model256 *m)
 {
     int i;
 
     for (i = 0; i < 255; i++)
         m->weights[i] = 1;
     m->weights[255] = 0;
 
     m->tot_weight   = 0;
     m->upd_val      = 256;
     m->till_rescale = 1;
     model256_update(m, 255);
     m->till_rescale =
     m->upd_val      = (256 + 6) >> 1;
 }
 
 static av_cold void model256_init(Model256 *m)
 {
     m->max_upd_val = 8 * 256 + 48;
     m->sec_size    = (1 << 6) + 2;
 
     model256_reset(m);
 }
 
 static void rac_init(RangeCoder *c, const uint8_t *src, int size)
 {
     int i;
 
     c->src       = src;
     c->src_end   = src + size;
     c->low       = 0;
     for (i = 0; i < FFMIN(size, 4); i++)
         c->low = (c->low << 8) | *c->src++;
     c->range     = 0xFFFFFFFF;
     c->got_error = 0;
 }
 
 static void rac_normalise(RangeCoder *c)
 {
     for (;;) {
         c->range <<= 8;
         c->low   <<= 8;
         if (c->src < c->src_end) {
             c->low |= *c->src++;
         } else if (!c->low) {
             c->got_error = 1;

             c->low = 1;

         }
         if (c->range >= RAC_BOTTOM)
             return;
     }
 }
 
 static int rac_get_bit(RangeCoder *c)
 {
     int bit;
 
     c->range >>= 1;
 
     bit = (c->range <= c->low);
     if (bit)
         c->low -= c->range;
 
     if (c->range < RAC_BOTTOM)
         rac_normalise(c);
 
     return bit;
 }
 
 static int rac_get_bits(RangeCoder *c, int nbits)
 {
     int val;
 
     c->range >>= nbits;
     val = c->low / c->range;
     c->low -= c->range * val;
 
     if (c->range < RAC_BOTTOM)
         rac_normalise(c);
 
     return val;
 }
 
 static int rac_get_model2_sym(RangeCoder *c, Model2 *m)
 {
     int bit, helper;
 
     helper = m->zero_freq * (c->range >> MODEL2_SCALE);
     bit    = (c->low >= helper);
     if (bit) {
         c->low   -= helper;
         c->range -= helper;
     } else {
         c->range  = helper;
     }
 
     if (c->range < RAC_BOTTOM)
         rac_normalise(c);
 
     model2_update(m, bit);
 
     return bit;
 }
 
 static int rac_get_model_sym(RangeCoder *c, Model *m)
 {
     int prob, prob2, helper, val;
     int end, end2;
 
     prob       = 0;
     prob2      = c->range;
     c->range >>= MODEL_SCALE;
     val        = 0;
     end        = m->num_syms >> 1;
     end2       = m->num_syms;
     do {
         helper = m->freqs[end] * c->range;
         if (helper <= c->low) {
             val   = end;
             prob  = helper;
         } else {
             end2  = end;
             prob2 = helper;
         }
         end = (end2 + val) >> 1;
     } while (end != val);
     c->low  -= prob;
     c->range = prob2 - prob;
     if (c->range < RAC_BOTTOM)
         rac_normalise(c);
 
     model_update(m, val);
 
     return val;
 }
 
 static int rac_get_model256_sym(RangeCoder *c, Model256 *m)
 {
     int prob, prob2, helper, val;
     int start, end;
     int ssym;
 
     prob2      = c->range;
     c->range >>= MODEL_SCALE;
 
     helper     = c->low / c->range;
     ssym       = helper >> MODEL256_SEC_SCALE;
     val        = m->secondary[ssym];
 
     end = start = m->secondary[ssym + 1] + 1;
     while (end > val + 1) {
         ssym = (end + val) >> 1;
         if (m->freqs[ssym] <= helper) {
             end = start;
             val = ssym;
         } else {
             end   = (end + val) >> 1;
             start = ssym;
         }
     }
     prob = m->freqs[val] * c->range;
     if (val != 255)
         prob2 = m->freqs[val + 1] * c->range;
 
     c->low  -= prob;
     c->range = prob2 - prob;
     if (c->range < RAC_BOTTOM)
         rac_normalise(c);
 
     model256_update(m, val);
 
     return val;
 }
 
 static int decode_block_type(RangeCoder *c, BlockTypeContext *bt)
 {
     bt->last_type = rac_get_model_sym(c, &bt->bt_model[bt->last_type]);
 
     return bt->last_type;
 }
 
 static int decode_coeff(RangeCoder *c, Model *m)
 {
     int val, sign;
 
     val = rac_get_model_sym(c, m);
     if (val) {
         sign = rac_get_bit(c);
         if (val > 1) {
             val--;
             val = (1 << val) + rac_get_bits(c, val);
         }
         if (!sign)
             val = -val;
     }
 
     return val;
 }
 
 static void decode_fill_block(RangeCoder *c, FillBlockCoder *fc,
                               uint8_t *dst, int stride, int block_size)
 {
     int i;
 
     fc->fill_val += decode_coeff(c, &fc->coef_model);
 
     for (i = 0; i < block_size; i++, dst += stride)
         memset(dst, fc->fill_val, block_size);
 }
 
 static void decode_image_block(RangeCoder *c, ImageBlockCoder *ic,
                                uint8_t *dst, int stride, int block_size)
 {
     int i, j;
     int vec_size;
     int vec[4];
     int prev_line[16];
     int A, B, C;
 
     vec_size = rac_get_model_sym(c, &ic->vec_size_model) + 2;
     for (i = 0; i < vec_size; i++)
         vec[i] = rac_get_model256_sym(c, &ic->vec_entry_model);
     for (; i < 4; i++)
         vec[i] = 0;
     memset(prev_line, 0, sizeof(prev_line));
 
     for (j = 0; j < block_size; j++) {
         A = 0;
         B = 0;
         for (i = 0; i < block_size; i++) {
             C = B;
             B = prev_line[i];
             A = rac_get_model_sym(c, &ic->vq_model[A + B * 5 + C * 25]);
 
             prev_line[i] = A;
             if (A < 4)
                dst[i] = vec[A];
             else
                dst[i] = rac_get_model256_sym(c, &ic->esc_model);
         }
         dst += stride;
     }
 }
 
 static int decode_dct(RangeCoder *c, DCTBlockCoder *bc, int *block,
                       int bx, int by)
 {
     int skip, val, sign, pos = 1, zz_pos, dc;
     int blk_pos = bx + by * bc->prev_dc_stride;
 
     memset(block, 0, sizeof(*block) * 64);
 
     dc = decode_coeff(c, &bc->dc_model);
     if (by) {
         if (bx) {
             int l, tl, t;
 
             l  = bc->prev_dc[blk_pos - 1];
             tl = bc->prev_dc[blk_pos - 1 - bc->prev_dc_stride];
             t  = bc->prev_dc[blk_pos     - bc->prev_dc_stride];
 
             if (FFABS(t - tl) <= FFABS(l - tl))
                 dc += l;
             else
                 dc += t;
         } else {
             dc += bc->prev_dc[blk_pos - bc->prev_dc_stride];
         }
     } else if (bx) {
         dc += bc->prev_dc[bx - 1];
     }
     bc->prev_dc[blk_pos] = dc;
     block[0]             = dc * bc->qmat[0];
 
     while (pos < 64) {
         val = rac_get_model256_sym(c, &bc->ac_model);
         if (!val)
             return 0;
         if (val == 0xF0) {
             pos += 16;
             continue;
         }
         skip = val >> 4;
         val  = val & 0xF;
         if (!val)
             return -1;
         pos += skip;
         if (pos >= 64)
             return -1;
 
         sign = rac_get_model2_sym(c, &bc->sign_model);
         if (val > 1) {
             val--;
             val = (1 << val) + rac_get_bits(c, val);
         }
         if (!sign)
             val = -val;
 

         zz_pos = ff_zigzag_direct[pos];

         block[zz_pos] = val * bc->qmat[zz_pos];
         pos++;
     }
 
     return pos == 64 ? 0 : -1;
 }
 
 static void decode_dct_block(RangeCoder *c, DCTBlockCoder *bc,
                              uint8_t *dst, int stride, int block_size,
                              int *block, int mb_x, int mb_y)
 {
     int i, j;
     int bx, by;
     int nblocks = block_size >> 3;
 
     bx = mb_x * nblocks;
     by = mb_y * nblocks;
 
     for (j = 0; j < nblocks; j++) {
         for (i = 0; i < nblocks; i++) {
             if (decode_dct(c, bc, block, bx + i, by + j)) {
                 c->got_error = 1;
                 return;
             }

             ff_mss34_dct_put(dst + i * 8, stride, block);

         }
         dst += 8 * stride;
     }
 }
 
 static void decode_haar_block(RangeCoder *c, HaarBlockCoder *hc,
                               uint8_t *dst, int stride, int block_size,
                               int *block)
 {
     const int hsize = block_size >> 1;
     int A, B, C, D, t1, t2, t3, t4;
     int i, j;
 
     for (j = 0; j < block_size; j++) {
         for (i = 0; i < block_size; i++) {
             if (i < hsize && j < hsize)
                 block[i] = rac_get_model256_sym(c, &hc->coef_model);
             else
                 block[i] = decode_coeff(c, &hc->coef_hi_model);
             block[i] *= hc->scale;
         }
         block += block_size;
     }
     block -= block_size * block_size;
 
     for (j = 0; j < hsize; j++) {
         for (i = 0; i < hsize; i++) {
             A = block[i];
             B = block[i + hsize];
             C = block[i + hsize * block_size];
             D = block[i + hsize * block_size + hsize];
 
             t1 = A - B;
             t2 = C - D;
             t3 = A + B;
             t4 = C + D;
             dst[i * 2]              = av_clip_uint8(t1 - t2);
             dst[i * 2 + stride]     = av_clip_uint8(t1 + t2);
             dst[i * 2 + 1]          = av_clip_uint8(t3 - t4);
             dst[i * 2 + 1 + stride] = av_clip_uint8(t3 + t4);
         }
         block += block_size;
         dst   += stride * 2;
     }
 }
 
 static void reset_coders(MSS3Context *ctx, int quality)
 {
     int i, j;
 
     for (i = 0; i < 3; i++) {
         ctx->btype[i].last_type = SKIP_BLOCK;
         for (j = 0; j < 5; j++)
             model_reset(&ctx->btype[i].bt_model[j]);
         ctx->fill_coder[i].fill_val = 0;
         model_reset(&ctx->fill_coder[i].coef_model);
         model256_reset(&ctx->image_coder[i].esc_model);
         model256_reset(&ctx->image_coder[i].vec_entry_model);
         model_reset(&ctx->image_coder[i].vec_size_model);
         for (j = 0; j < 125; j++)
             model_reset(&ctx->image_coder[i].vq_model[j]);
         if (ctx->dct_coder[i].quality != quality) {
             ctx->dct_coder[i].quality = quality;

             ff_mss34_gen_quant_mat(ctx->dct_coder[i].qmat, quality, !i);

         }
         memset(ctx->dct_coder[i].prev_dc, 0,
                sizeof(*ctx->dct_coder[i].prev_dc) *
                ctx->dct_coder[i].prev_dc_stride *
                ctx->dct_coder[i].prev_dc_height);
         model_reset(&ctx->dct_coder[i].dc_model);
         model2_reset(&ctx->dct_coder[i].sign_model);
         model256_reset(&ctx->dct_coder[i].ac_model);
         if (ctx->haar_coder[i].quality != quality) {
             ctx->haar_coder[i].quality = quality;
             ctx->haar_coder[i].scale   = 17 - 7 * quality / 50;
         }
         model_reset(&ctx->haar_coder[i].coef_hi_model);
         model256_reset(&ctx->haar_coder[i].coef_model);
     }
 }
 
 static av_cold void init_coders(MSS3Context *ctx)
 {
     int i, j;
 
     for (i = 0; i < 3; i++) {
         for (j = 0; j < 5; j++)
             model_init(&ctx->btype[i].bt_model[j], 5);
         model_init(&ctx->fill_coder[i].coef_model, 12);
         model256_init(&ctx->image_coder[i].esc_model);
         model256_init(&ctx->image_coder[i].vec_entry_model);
         model_init(&ctx->image_coder[i].vec_size_model, 3);
         for (j = 0; j < 125; j++)
             model_init(&ctx->image_coder[i].vq_model[j], 5);
         model_init(&ctx->dct_coder[i].dc_model, 12);
         model256_init(&ctx->dct_coder[i].ac_model);
         model_init(&ctx->haar_coder[i].coef_hi_model, 12);
         model256_init(&ctx->haar_coder[i].coef_model);
     }
 }
 

 static int mss3_decode_frame(AVCodecContext *avctx, void *data, int *got_frame,

                              AVPacket *avpkt)
 {
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     MSS3Context *c = avctx->priv_data;
     RangeCoder *acoder = &c->coder;
     GetByteContext gb;
     uint8_t *dst[3];
     int dec_width, dec_height, dec_x, dec_y, quality, keyframe;
     int x, y, i, mb_width, mb_height, blk_size, btype;
     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(&gb, buf, buf_size);
     keyframe   = bytestream2_get_be32(&gb);
     if (keyframe & ~0x301) {
         av_log(avctx, AV_LOG_ERROR, "Invalid frame type %X\n", keyframe);
         return AVERROR_INVALIDDATA;
     }
     keyframe   = !(keyframe & 1);
     bytestream2_skip(&gb, 6);
     dec_x      = bytestream2_get_be16(&gb);
     dec_y      = bytestream2_get_be16(&gb);
     dec_width  = bytestream2_get_be16(&gb);
     dec_height = bytestream2_get_be16(&gb);
 
     if (dec_x + dec_width > avctx->width ||
         dec_y + dec_height > avctx->height ||
         (dec_width | dec_height) & 0xF) {
         av_log(avctx, AV_LOG_ERROR, "Invalid frame dimensions %dx%d +%d,%d\n",
                dec_width, dec_height, dec_x, dec_y);
         return AVERROR_INVALIDDATA;
     }
     bytestream2_skip(&gb, 4);
     quality    = bytestream2_get_byte(&gb);
     if (quality < 1 || quality > 100) {
         av_log(avctx, AV_LOG_ERROR, "Invalid quality setting %d\n", quality);
         return AVERROR_INVALIDDATA;
     }
     bytestream2_skip(&gb, 4);
 
     if (keyframe && !bytestream2_get_bytes_left(&gb)) {
         av_log(avctx, AV_LOG_ERROR, "Keyframe without data found\n");
         return AVERROR_INVALIDDATA;
     }
     if (!keyframe && c->got_error)
         return buf_size;
     c->got_error = 0;
 

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

         return ret;

     c->pic->key_frame = keyframe;
     c->pic->pict_type = keyframe ? AV_PICTURE_TYPE_I : AV_PICTURE_TYPE_P;

     if (!bytestream2_get_bytes_left(&gb)) {

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

             return ret;

         *got_frame      = 1;

 
         return buf_size;
     }
 
     reset_coders(c, quality);
 
     rac_init(acoder, buf + HEADER_SIZE, buf_size - HEADER_SIZE);
 
     mb_width  = dec_width  >> 4;
     mb_height = dec_height >> 4;

     dst[0] = c->pic->data[0] + dec_x     +  dec_y      * c->pic->linesize[0];
     dst[1] = c->pic->data[1] + dec_x / 2 + (dec_y / 2) * c->pic->linesize[1];
     dst[2] = c->pic->data[2] + dec_x / 2 + (dec_y / 2) * c->pic->linesize[2];

     for (y = 0; y < mb_height; y++) {
         for (x = 0; x < mb_width; x++) {
             for (i = 0; i < 3; i++) {
                 blk_size = 8 << !i;
 
                 btype = decode_block_type(acoder, c->btype + i);
                 switch (btype) {
                 case FILL_BLOCK:
                     decode_fill_block(acoder, c->fill_coder + i,
                                       dst[i] + x * blk_size,

                                       c->pic->linesize[i], blk_size);

                     break;
                 case IMAGE_BLOCK:
                     decode_image_block(acoder, c->image_coder + i,
                                        dst[i] + x * blk_size,

                                        c->pic->linesize[i], blk_size);

                     break;
                 case DCT_BLOCK:
                     decode_dct_block(acoder, c->dct_coder + i,
                                      dst[i] + x * blk_size,

                                      c->pic->linesize[i], blk_size,

                                      c->dctblock, x, y);
                     break;
                 case HAAR_BLOCK:
                     decode_haar_block(acoder, c->haar_coder + i,
                                       dst[i] + x * blk_size,

                                       c->pic->linesize[i], blk_size,

                                       c->hblock);
                     break;
                 }
                 if (c->got_error || acoder->got_error) {
                     av_log(avctx, AV_LOG_ERROR, "Error decoding block %d,%d\n",
                            x, y);
                     c->got_error = 1;
                     return AVERROR_INVALIDDATA;
                 }
             }
         }

         dst[0] += c->pic->linesize[0] * 16;
         dst[1] += c->pic->linesize[1] * 8;
         dst[2] += c->pic->linesize[2] * 8;

     }
 

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

         return ret;
 

     *got_frame      = 1;

 
     return buf_size;
 }
 

 static av_cold int mss3_decode_end(AVCodecContext *avctx)
 {
     MSS3Context * const c = avctx->priv_data;
     int i;
 
     av_frame_free(&c->pic);
     for (i = 0; i < 3; i++)
         av_freep(&c->dct_coder[i].prev_dc);
 
     return 0;
 }
 

 static av_cold int mss3_decode_init(AVCodecContext *avctx)
 {
     MSS3Context * const c = avctx->priv_data;
     int i;
 
     c->avctx = avctx;
 
     if ((avctx->width & 0xF) || (avctx->height & 0xF)) {
         av_log(avctx, AV_LOG_ERROR,
                "Image dimensions should be a multiple of 16.\n");
         return AVERROR_INVALIDDATA;
     }
 
     c->got_error = 0;
     for (i = 0; i < 3; i++) {
         int b_width  = avctx->width  >> (2 + !!i);
         int b_height = avctx->height >> (2 + !!i);
         c->dct_coder[i].prev_dc_stride = b_width;
         c->dct_coder[i].prev_dc_height = b_height;
         c->dct_coder[i].prev_dc = av_malloc(sizeof(*c->dct_coder[i].prev_dc) *
                                             b_width * b_height);
         if (!c->dct_coder[i].prev_dc) {
             av_log(avctx, AV_LOG_ERROR, "Cannot allocate buffer\n");

             av_frame_free(&c->pic);

             while (i >= 0) {
                 av_freep(&c->dct_coder[i].prev_dc);
                 i--;
             }
             return AVERROR(ENOMEM);
         }
     }
 

     c->pic = av_frame_alloc();
     if (!c->pic) {
         mss3_decode_end(avctx);
         return AVERROR(ENOMEM);
     }
 

     avctx->pix_fmt     = AV_PIX_FMT_YUV420P;

 
     init_coders(c);
 
     return 0;
 }
 
 AVCodec ff_msa1_decoder = {
     .name           = "msa1",

     .long_name      = NULL_IF_CONFIG_SMALL("MS ATC Screen"),

     .type           = AVMEDIA_TYPE_VIDEO,

     .id             = AV_CODEC_ID_MSA1,

     .priv_data_size = sizeof(MSS3Context),
     .init           = mss3_decode_init,
     .close          = mss3_decode_end,
     .decode         = mss3_decode_frame,
     .capabilities   = CODEC_CAP_DR1,
 };