git.sesse.net Git - ffmpeg/blob - libavcodec/snowdec.c

   1 /*
   2  * Copyright (C) 2004 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #include "libavutil/intmath.h"
  22 #include "libavutil/log.h"
  23 #include "libavutil/opt.h"
  24 #include "avcodec.h"
  25 #include "dsputil.h"
  26 #include "dwt.h"
  27 #include "snow.h"
  28
  29 #include "rangecoder.h"
  30 #include "mathops.h"
  31
  32 #include "mpegvideo.h"
  33 #include "h263.h"
  34
  35 #undef NDEBUG
  36 #include <assert.h>
  37
  38 static av_always_inline void predict_slice_buffered(SnowContext *s, slice_buffer * sb, IDWTELEM * old_buffer, int plane_index, int add, int mb_y){
  39     Plane *p= &s->plane[plane_index];
  40     const int mb_w= s->b_width  << s->block_max_depth;
  41     const int mb_h= s->b_height << s->block_max_depth;
  42     int x, y, mb_x;
  43     int block_size = MB_SIZE >> s->block_max_depth;
  44     int block_w    = plane_index ? block_size/2 : block_size;
  45     const uint8_t *obmc  = plane_index ? obmc_tab[s->block_max_depth+1] : obmc_tab[s->block_max_depth];
  46     int obmc_stride= plane_index ? block_size : 2*block_size;
  47     int ref_stride= s->current_picture.linesize[plane_index];
  48     uint8_t *dst8= s->current_picture.data[plane_index];
  49     int w= p->width;
  50     int h= p->height;
  51
  52     if(s->keyframe || (s->avctx->debug&512)){
  53         if(mb_y==mb_h)
  54             return;
  55
  56         if(add){
  57             for(y=block_w*mb_y; y<FFMIN(h,block_w*(mb_y+1)); y++){
  58 //                DWTELEM * line = slice_buffer_get_line(sb, y);
  59                 IDWTELEM * line = sb->line[y];
  60                 for(x=0; x<w; x++){
  61 //                    int v= buf[x + y*w] + (128<<FRAC_BITS) + (1<<(FRAC_BITS-1));
  62                     int v= line[x] + (128<<FRAC_BITS) + (1<<(FRAC_BITS-1));
  63                     v >>= FRAC_BITS;
  64                     if(v&(~255)) v= ~(v>>31);
  65                     dst8[x + y*ref_stride]= v;
  66                 }
  67             }
  68         }else{
  69             for(y=block_w*mb_y; y<FFMIN(h,block_w*(mb_y+1)); y++){
  70 //                DWTELEM * line = slice_buffer_get_line(sb, y);
  71                 IDWTELEM * line = sb->line[y];
  72                 for(x=0; x<w; x++){
  73                     line[x] -= 128 << FRAC_BITS;
  74 //                    buf[x + y*w]-= 128<<FRAC_BITS;
  75                 }
  76             }
  77         }
  78
  79         return;
  80     }
  81
  82     for(mb_x=0; mb_x<=mb_w; mb_x++){
  83         add_yblock(s, 1, sb, old_buffer, dst8, obmc,
  84                    block_w*mb_x - block_w/2,
  85                    block_w*mb_y - block_w/2,
  86                    block_w, block_w,
  87                    w, h,
  88                    w, ref_stride, obmc_stride,
  89                    mb_x - 1, mb_y - 1,
  90                    add, 0, plane_index);
  91     }
  92 }
  93
  94 static inline void decode_subband_slice_buffered(SnowContext *s, SubBand *b, slice_buffer * sb, int start_y, int h, int save_state[1]){
  95     const int w= b->width;
  96     int y;
  97     const int qlog= av_clip(s->qlog + b->qlog, 0, QROOT*16);
  98     int qmul= qexp[qlog&(QROOT-1)]<<(qlog>>QSHIFT);
  99     int qadd= (s->qbias*qmul)>>QBIAS_SHIFT;
 100     int new_index = 0;
 101
 102     if(b->ibuf == s->spatial_idwt_buffer || s->qlog == LOSSLESS_QLOG){
 103         qadd= 0;
 104         qmul= 1<<QEXPSHIFT;
 105     }
 106
 107     /* If we are on the second or later slice, restore our index. */
 108     if (start_y != 0)
 109         new_index = save_state[0];
 110
 111
 112     for(y=start_y; y<h; y++){
 113         int x = 0;
 114         int v;
 115         IDWTELEM * line = slice_buffer_get_line(sb, y * b->stride_line + b->buf_y_offset) + b->buf_x_offset;
 116         memset(line, 0, b->width*sizeof(IDWTELEM));
 117         v = b->x_coeff[new_index].coeff;
 118         x = b->x_coeff[new_index++].x;
 119         while(x < w){
 120             register int t= ( (v>>1)*qmul + qadd)>>QEXPSHIFT;
 121             register int u= -(v&1);
 122             line[x] = (t^u) - u;
 123
 124             v = b->x_coeff[new_index].coeff;
 125             x = b->x_coeff[new_index++].x;
 126         }
 127     }
 128
 129     /* Save our variables for the next slice. */
 130     save_state[0] = new_index;
 131
 132     return;
 133 }
 134
 135 static void decode_q_branch(SnowContext *s, int level, int x, int y){
 136     const int w= s->b_width << s->block_max_depth;
 137     const int rem_depth= s->block_max_depth - level;
 138     const int index= (x + y*w) << rem_depth;
 139     int trx= (x+1)<<rem_depth;
 140     const BlockNode *left  = x ? &s->block[index-1] : &null_block;
 141     const BlockNode *top   = y ? &s->block[index-w] : &null_block;
 142     const BlockNode *tl    = y && x ? &s->block[index-w-1] : left;
 143     const BlockNode *tr    = y && trx<w && ((x&1)==0 || level==0) ? &s->block[index-w+(1<<rem_depth)] : tl; //FIXME use lt
 144     int s_context= 2*left->level + 2*top->level + tl->level + tr->level;
 145
 146     if(s->keyframe){
 147         set_blocks(s, level, x, y, null_block.color[0], null_block.color[1], null_block.color[2], null_block.mx, null_block.my, null_block.ref, BLOCK_INTRA);
 148         return;
 149     }
 150
 151     if(level==s->block_max_depth || get_rac(&s->c, &s->block_state[4 + s_context])){
 152         int type, mx, my;
 153         int l = left->color[0];
 154         int cb= left->color[1];
 155         int cr= left->color[2];
 156         int ref = 0;
 157         int ref_context= av_log2(2*left->ref) + av_log2(2*top->ref);
 158         int mx_context= av_log2(2*FFABS(left->mx - top->mx)) + 0*av_log2(2*FFABS(tr->mx - top->mx));
 159         int my_context= av_log2(2*FFABS(left->my - top->my)) + 0*av_log2(2*FFABS(tr->my - top->my));
 160
 161         type= get_rac(&s->c, &s->block_state[1 + left->type + top->type]) ? BLOCK_INTRA : 0;
 162
 163         if(type){
 164             pred_mv(s, &mx, &my, 0, left, top, tr);
 165             l += get_symbol(&s->c, &s->block_state[32], 1);
 166             cb+= get_symbol(&s->c, &s->block_state[64], 1);
 167             cr+= get_symbol(&s->c, &s->block_state[96], 1);
 168         }else{
 169             if(s->ref_frames > 1)
 170                 ref= get_symbol(&s->c, &s->block_state[128 + 1024 + 32*ref_context], 0);
 171             pred_mv(s, &mx, &my, ref, left, top, tr);
 172             mx+= get_symbol(&s->c, &s->block_state[128 + 32*(mx_context + 16*!!ref)], 1);
 173             my+= get_symbol(&s->c, &s->block_state[128 + 32*(my_context + 16*!!ref)], 1);
 174         }
 175         set_blocks(s, level, x, y, l, cb, cr, mx, my, ref, type);
 176     }else{
 177         decode_q_branch(s, level+1, 2*x+0, 2*y+0);
 178         decode_q_branch(s, level+1, 2*x+1, 2*y+0);
 179         decode_q_branch(s, level+1, 2*x+0, 2*y+1);
 180         decode_q_branch(s, level+1, 2*x+1, 2*y+1);
 181     }
 182 }
 183
 184 static void dequantize_slice_buffered(SnowContext *s, slice_buffer * sb, SubBand *b, IDWTELEM *src, int stride, int start_y, int end_y){
 185     const int w= b->width;
 186     const int qlog= av_clip(s->qlog + b->qlog, 0, QROOT*16);
 187     const int qmul= qexp[qlog&(QROOT-1)]<<(qlog>>QSHIFT);
 188     const int qadd= (s->qbias*qmul)>>QBIAS_SHIFT;
 189     int x,y;
 190
 191     if(s->qlog == LOSSLESS_QLOG) return;
 192
 193     for(y=start_y; y<end_y; y++){
 194 //        DWTELEM * line = slice_buffer_get_line_from_address(sb, src + (y * stride));
 195         IDWTELEM * line = slice_buffer_get_line(sb, (y * b->stride_line) + b->buf_y_offset) + b->buf_x_offset;
 196         for(x=0; x<w; x++){
 197             int i= line[x];
 198             if(i<0){
 199                 line[x]= -((-i*qmul + qadd)>>(QEXPSHIFT)); //FIXME try different bias
 200             }else if(i>0){
 201                 line[x]=  (( i*qmul + qadd)>>(QEXPSHIFT));
 202             }
 203         }
 204     }
 205 }
 206
 207 static void correlate_slice_buffered(SnowContext *s, slice_buffer * sb, SubBand *b, IDWTELEM *src, int stride, int inverse, int use_median, int start_y, int end_y){
 208     const int w= b->width;
 209     int x,y;
 210
 211     IDWTELEM * line=0; // silence silly "could be used without having been initialized" warning
 212     IDWTELEM * prev;
 213
 214     if (start_y != 0)
 215         line = slice_buffer_get_line(sb, ((start_y - 1) * b->stride_line) + b->buf_y_offset) + b->buf_x_offset;
 216
 217     for(y=start_y; y<end_y; y++){
 218         prev = line;
 219 //        line = slice_buffer_get_line_from_address(sb, src + (y * stride));
 220         line = slice_buffer_get_line(sb, (y * b->stride_line) + b->buf_y_offset) + b->buf_x_offset;
 221         for(x=0; x<w; x++){
 222             if(x){
 223                 if(use_median){
 224                     if(y && x+1<w) line[x] += mid_pred(line[x - 1], prev[x], prev[x + 1]);
 225                     else  line[x] += line[x - 1];
 226                 }else{
 227                     if(y) line[x] += mid_pred(line[x - 1], prev[x], line[x - 1] + prev[x] - prev[x - 1]);
 228                     else  line[x] += line[x - 1];
 229                 }
 230             }else{
 231                 if(y) line[x] += prev[x];
 232             }
 233         }
 234     }
 235 }
 236
 237 static void decode_qlogs(SnowContext *s){
 238     int plane_index, level, orientation;
 239
 240     for(plane_index=0; plane_index<3; plane_index++){
 241         for(level=0; level<s->spatial_decomposition_count; level++){
 242             for(orientation=level ? 1:0; orientation<4; orientation++){
 243                 int q;
 244                 if     (plane_index==2) q= s->plane[1].band[level][orientation].qlog;
 245                 else if(orientation==2) q= s->plane[plane_index].band[level][1].qlog;
 246                 else                    q= get_symbol(&s->c, s->header_state, 1);
 247                 s->plane[plane_index].band[level][orientation].qlog= q;
 248             }
 249         }
 250     }
 251 }
 252
 253 #define GET_S(dst, check) \
 254     tmp= get_symbol(&s->c, s->header_state, 0);\
 255     if(!(check)){\
 256         av_log(s->avctx, AV_LOG_ERROR, "Error " #dst " is %d\n", tmp);\
 257         return -1;\
 258     }\
 259     dst= tmp;
 260
 261 static int decode_header(SnowContext *s){
 262     int plane_index, tmp;
 263     uint8_t kstate[32];
 264
 265     memset(kstate, MID_STATE, sizeof(kstate));
 266
 267     s->keyframe= get_rac(&s->c, kstate);
 268     if(s->keyframe || s->always_reset){
 269         ff_snow_reset_contexts(s);
 270         s->spatial_decomposition_type=
 271         s->qlog=
 272         s->qbias=
 273         s->mv_scale=
 274         s->block_max_depth= 0;
 275     }
 276     if(s->keyframe){
 277         GET_S(s->version, tmp <= 0U)
 278         s->always_reset= get_rac(&s->c, s->header_state);
 279         s->temporal_decomposition_type= get_symbol(&s->c, s->header_state, 0);
 280         s->temporal_decomposition_count= get_symbol(&s->c, s->header_state, 0);
 281         GET_S(s->spatial_decomposition_count, 0 < tmp && tmp <= MAX_DECOMPOSITIONS)
 282         s->colorspace_type= get_symbol(&s->c, s->header_state, 0);
 283         s->chroma_h_shift= get_symbol(&s->c, s->header_state, 0);
 284         s->chroma_v_shift= get_symbol(&s->c, s->header_state, 0);
 285         s->spatial_scalability= get_rac(&s->c, s->header_state);
 286 //        s->rate_scalability= get_rac(&s->c, s->header_state);
 287         GET_S(s->max_ref_frames, tmp < (unsigned)MAX_REF_FRAMES)
 288         s->max_ref_frames++;
 289
 290         decode_qlogs(s);
 291     }
 292
 293     if(!s->keyframe){
 294         if(get_rac(&s->c, s->header_state)){
 295             for(plane_index=0; plane_index<2; plane_index++){
 296                 int htaps, i, sum=0;
 297                 Plane *p= &s->plane[plane_index];
 298                 p->diag_mc= get_rac(&s->c, s->header_state);
 299                 htaps= get_symbol(&s->c, s->header_state, 0)*2 + 2;
 300                 if((unsigned)htaps > HTAPS_MAX || htaps==0)
 301                     return -1;
 302                 p->htaps= htaps;
 303                 for(i= htaps/2; i; i--){
 304                     p->hcoeff[i]= get_symbol(&s->c, s->header_state, 0) * (1-2*(i&1));
 305                     sum += p->hcoeff[i];
 306                 }
 307                 p->hcoeff[0]= 32-sum;
 308             }
 309             s->plane[2].diag_mc= s->plane[1].diag_mc;
 310             s->plane[2].htaps  = s->plane[1].htaps;
 311             memcpy(s->plane[2].hcoeff, s->plane[1].hcoeff, sizeof(s->plane[1].hcoeff));
 312         }
 313         if(get_rac(&s->c, s->header_state)){
 314             GET_S(s->spatial_decomposition_count, 0 < tmp && tmp <= MAX_DECOMPOSITIONS)
 315             decode_qlogs(s);
 316         }
 317     }
 318
 319     s->spatial_decomposition_type+= get_symbol(&s->c, s->header_state, 1);
 320     if(s->spatial_decomposition_type > 1U){
 321         av_log(s->avctx, AV_LOG_ERROR, "spatial_decomposition_type %d not supported", s->spatial_decomposition_type);
 322         return -1;
 323     }
 324     if(FFMIN(s->avctx-> width>>s->chroma_h_shift,
 325              s->avctx->height>>s->chroma_v_shift) >> (s->spatial_decomposition_count-1) <= 0){
 326         av_log(s->avctx, AV_LOG_ERROR, "spatial_decomposition_count %d too large for size", s->spatial_decomposition_count);
 327         return -1;
 328     }
 329
 330     s->qlog           += get_symbol(&s->c, s->header_state, 1);
 331     s->mv_scale       += get_symbol(&s->c, s->header_state, 1);
 332     s->qbias          += get_symbol(&s->c, s->header_state, 1);
 333     s->block_max_depth+= get_symbol(&s->c, s->header_state, 1);
 334     if(s->block_max_depth > 1 || s->block_max_depth < 0){
 335         av_log(s->avctx, AV_LOG_ERROR, "block_max_depth= %d is too large", s->block_max_depth);
 336         s->block_max_depth= 0;
 337         return -1;
 338     }
 339
 340     return 0;
 341 }
 342
 343 static av_cold int decode_init(AVCodecContext *avctx)
 344 {
 345     avctx->pix_fmt= PIX_FMT_YUV420P;
 346
 347     ff_snow_common_init(avctx);
 348
 349     return 0;
 350 }
 351
 352 static void decode_blocks(SnowContext *s){
 353     int x, y;
 354     int w= s->b_width;
 355     int h= s->b_height;
 356
 357     for(y=0; y<h; y++){
 358         for(x=0; x<w; x++){
 359             decode_q_branch(s, 0, x, y);
 360         }
 361     }
 362 }
 363
 364 static int decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt){
 365     const uint8_t *buf = avpkt->data;
 366     int buf_size = avpkt->size;
 367     SnowContext *s = avctx->priv_data;
 368     RangeCoder * const c= &s->c;
 369     int bytes_read;
 370     AVFrame *picture = data;
 371     int level, orientation, plane_index;
 372
 373     ff_init_range_decoder(c, buf, buf_size);
 374     ff_build_rac_states(c, 0.05*(1LL<<32), 256-8);
 375
 376     s->current_picture.pict_type= AV_PICTURE_TYPE_I; //FIXME I vs. P
 377     if(decode_header(s)<0)
 378         return -1;
 379     ff_snow_common_init_after_header(avctx);
 380
 381     // realloc slice buffer for the case that spatial_decomposition_count changed
 382     ff_slice_buffer_destroy(&s->sb);
 383     ff_slice_buffer_init(&s->sb, s->plane[0].height, (MB_SIZE >> s->block_max_depth) + s->spatial_decomposition_count * 8 + 1, s->plane[0].width, s->spatial_idwt_buffer);
 384
 385     for(plane_index=0; plane_index<3; plane_index++){
 386         Plane *p= &s->plane[plane_index];
 387         p->fast_mc= p->diag_mc && p->htaps==6 && p->hcoeff[0]==40
 388                                               && p->hcoeff[1]==-10
 389                                               && p->hcoeff[2]==2;
 390     }
 391
 392     ff_snow_alloc_blocks(s);
 393
 394     if(ff_snow_frame_start(s) < 0)
 395         return -1;
 396     //keyframe flag duplication mess FIXME
 397     if(avctx->debug&FF_DEBUG_PICT_INFO)
 398         av_log(avctx, AV_LOG_ERROR, "keyframe:%d qlog:%d\n", s->keyframe, s->qlog);
 399
 400     decode_blocks(s);
 401
 402     for(plane_index=0; plane_index<3; plane_index++){
 403         Plane *p= &s->plane[plane_index];
 404         int w= p->width;
 405         int h= p->height;
 406         int x, y;
 407         int decode_state[MAX_DECOMPOSITIONS][4][1]; /* Stored state info for unpack_coeffs. 1 variable per instance. */
 408
 409         if(s->avctx->debug&2048){
 410             memset(s->spatial_dwt_buffer, 0, sizeof(DWTELEM)*w*h);
 411             predict_plane(s, s->spatial_idwt_buffer, plane_index, 1);
 412
 413             for(y=0; y<h; y++){
 414                 for(x=0; x<w; x++){
 415                     int v= s->current_picture.data[plane_index][y*s->current_picture.linesize[plane_index] + x];
 416                     s->mconly_picture.data[plane_index][y*s->mconly_picture.linesize[plane_index] + x]= v;
 417                 }
 418             }
 419         }
 420
 421         {
 422         for(level=0; level<s->spatial_decomposition_count; level++){
 423             for(orientation=level ? 1 : 0; orientation<4; orientation++){
 424                 SubBand *b= &p->band[level][orientation];
 425                 unpack_coeffs(s, b, b->parent, orientation);
 426             }
 427         }
 428         }
 429
 430         {
 431         const int mb_h= s->b_height << s->block_max_depth;
 432         const int block_size = MB_SIZE >> s->block_max_depth;
 433         const int block_w    = plane_index ? block_size/2 : block_size;
 434         int mb_y;
 435         DWTCompose cs[MAX_DECOMPOSITIONS];
 436         int yd=0, yq=0;
 437         int y;
 438         int end_y;
 439
 440         ff_spatial_idwt_buffered_init(cs, &s->sb, w, h, 1, s->spatial_decomposition_type, s->spatial_decomposition_count);
 441         for(mb_y=0; mb_y<=mb_h; mb_y++){
 442
 443             int slice_starty = block_w*mb_y;
 444             int slice_h = block_w*(mb_y+1);
 445             if (!(s->keyframe || s->avctx->debug&512)){
 446                 slice_starty = FFMAX(0, slice_starty - (block_w >> 1));
 447                 slice_h -= (block_w >> 1);
 448             }
 449
 450             for(level=0; level<s->spatial_decomposition_count; level++){
 451                 for(orientation=level ? 1 : 0; orientation<4; orientation++){
 452                     SubBand *b= &p->band[level][orientation];
 453                     int start_y;
 454                     int end_y;
 455                     int our_mb_start = mb_y;
 456                     int our_mb_end = (mb_y + 1);
 457                     const int extra= 3;
 458                     start_y = (mb_y ? ((block_w * our_mb_start) >> (s->spatial_decomposition_count - level)) + s->spatial_decomposition_count - level + extra: 0);
 459                     end_y = (((block_w * our_mb_end) >> (s->spatial_decomposition_count - level)) + s->spatial_decomposition_count - level + extra);
 460                     if (!(s->keyframe || s->avctx->debug&512)){
 461                         start_y = FFMAX(0, start_y - (block_w >> (1+s->spatial_decomposition_count - level)));
 462                         end_y = FFMAX(0, end_y - (block_w >> (1+s->spatial_decomposition_count - level)));
 463                     }
 464                     start_y = FFMIN(b->height, start_y);
 465                     end_y = FFMIN(b->height, end_y);
 466
 467                     if (start_y != end_y){
 468                         if (orientation == 0){
 469                             SubBand * correlate_band = &p->band[0][0];
 470                             int correlate_end_y = FFMIN(b->height, end_y + 1);
 471                             int correlate_start_y = FFMIN(b->height, (start_y ? start_y + 1 : 0));
 472                             decode_subband_slice_buffered(s, correlate_band, &s->sb, correlate_start_y, correlate_end_y, decode_state[0][0]);
 473                             correlate_slice_buffered(s, &s->sb, correlate_band, correlate_band->ibuf, correlate_band->stride, 1, 0, correlate_start_y, correlate_end_y);
 474                             dequantize_slice_buffered(s, &s->sb, correlate_band, correlate_band->ibuf, correlate_band->stride, start_y, end_y);
 475                         }
 476                         else
 477                             decode_subband_slice_buffered(s, b, &s->sb, start_y, end_y, decode_state[level][orientation]);
 478                     }
 479                 }
 480             }
 481
 482             for(; yd<slice_h; yd+=4){
 483                 ff_spatial_idwt_buffered_slice(&s->dwt, cs, &s->sb, w, h, 1, s->spatial_decomposition_type, s->spatial_decomposition_count, yd);
 484             }
 485
 486             if(s->qlog == LOSSLESS_QLOG){
 487                 for(; yq<slice_h && yq<h; yq++){
 488                     IDWTELEM * line = slice_buffer_get_line(&s->sb, yq);
 489                     for(x=0; x<w; x++){
 490                         line[x] <<= FRAC_BITS;
 491                     }
 492                 }
 493             }
 494
 495             predict_slice_buffered(s, &s->sb, s->spatial_idwt_buffer, plane_index, 1, mb_y);
 496
 497             y = FFMIN(p->height, slice_starty);
 498             end_y = FFMIN(p->height, slice_h);
 499             while(y < end_y)
 500                 ff_slice_buffer_release(&s->sb, y++);
 501         }
 502
 503         ff_slice_buffer_flush(&s->sb);
 504         }
 505
 506     }
 507
 508     emms_c();
 509
 510     ff_snow_release_buffer(avctx);
 511
 512     if(!(s->avctx->debug&2048))
 513         *picture= s->current_picture;
 514     else
 515         *picture= s->mconly_picture;
 516
 517     *data_size = sizeof(AVFrame);
 518
 519     bytes_read= c->bytestream - c->bytestream_start;
 520     if(bytes_read ==0) av_log(s->avctx, AV_LOG_ERROR, "error at end of frame\n"); //FIXME
 521
 522     return bytes_read;
 523 }
 524
 525 static av_cold int decode_end(AVCodecContext *avctx)
 526 {
 527     SnowContext *s = avctx->priv_data;
 528
 529     ff_slice_buffer_destroy(&s->sb);
 530
 531     ff_snow_common_end(s);
 532
 533     return 0;
 534 }
 535
 536 AVCodec ff_snow_decoder = {
 537     .name           = "snow",
 538     .type           = AVMEDIA_TYPE_VIDEO,
 539     .id             = CODEC_ID_SNOW,
 540     .priv_data_size = sizeof(SnowContext),
 541     .init           = decode_init,
 542     .close          = decode_end,
 543     .decode         = decode_frame,
 544     .capabilities   = CODEC_CAP_DR1 /*| CODEC_CAP_DRAW_HORIZ_BAND*/,
 545     .long_name = NULL_IF_CONFIG_SMALL("Snow"),
 546 };