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 "snow_dwt.h"
  27 #include "internal.h"
  28 #include "snow.h"
  29
  30 #include "rangecoder.h"
  31 #include "mathops.h"
  32
  33 #include "mpegvideo.h"
  34 #include "h263.h"
  35
  36 static av_always_inline void predict_slice_buffered(SnowContext *s, slice_buffer * sb, IDWTELEM * old_buffer, int plane_index, int add, int mb_y){
  37     Plane *p= &s->plane[plane_index];
  38     const int mb_w= s->b_width  << s->block_max_depth;
  39     const int mb_h= s->b_height << s->block_max_depth;
  40     int x, y, mb_x;
  41     int block_size = MB_SIZE >> s->block_max_depth;
  42     int block_w    = plane_index ? block_size>>s->chroma_h_shift : block_size;
  43     int block_h    = plane_index ? block_size>>s->chroma_v_shift : block_size;
  44     const uint8_t *obmc  = plane_index ? ff_obmc_tab[s->block_max_depth+s->chroma_h_shift] : ff_obmc_tab[s->block_max_depth];
  45     int obmc_stride= plane_index ? (2*block_size)>>s->chroma_h_shift : 2*block_size;
  46     int ref_stride= s->current_picture->linesize[plane_index];
  47     uint8_t *dst8= s->current_picture->data[plane_index];
  48     int w= p->width;
  49     int h= p->height;
  50
  51     if(s->keyframe || (s->avctx->debug&512)){
  52         if(mb_y==mb_h)
  53             return;
  54
  55         if(add){
  56             for(y=block_h*mb_y; y<FFMIN(h,block_h*(mb_y+1)); y++){
  57 //                DWTELEM * line = slice_buffer_get_line(sb, y);
  58                 IDWTELEM * line = sb->line[y];
  59                 for(x=0; x<w; x++){
  60 //                    int v= buf[x + y*w] + (128<<FRAC_BITS) + (1<<(FRAC_BITS-1));
  61                     int v= line[x] + (128<<FRAC_BITS) + (1<<(FRAC_BITS-1));
  62                     v >>= FRAC_BITS;
  63                     if(v&(~255)) v= ~(v>>31);
  64                     dst8[x + y*ref_stride]= v;
  65                 }
  66             }
  67         }else{
  68             for(y=block_h*mb_y; y<FFMIN(h,block_h*(mb_y+1)); y++){
  69 //                DWTELEM * line = slice_buffer_get_line(sb, y);
  70                 IDWTELEM * line = sb->line[y];
  71                 for(x=0; x<w; x++){
  72                     line[x] -= 128 << FRAC_BITS;
  73 //                    buf[x + y*w]-= 128<<FRAC_BITS;
  74                 }
  75             }
  76         }
  77
  78         return;
  79     }
  80
  81     for(mb_x=0; mb_x<=mb_w; mb_x++){
  82         add_yblock(s, 1, sb, old_buffer, dst8, obmc,
  83                    block_w*mb_x - block_w/2,
  84                    block_h*mb_y - block_h/2,
  85                    block_w, block_h,
  86                    w, h,
  87                    w, ref_stride, obmc_stride,
  88                    mb_x - 1, mb_y - 1,
  89                    add, 0, plane_index);
  90     }
  91 }
  92
  93 static inline void decode_subband_slice_buffered(SnowContext *s, SubBand *b, slice_buffer * sb, int start_y, int h, int save_state[1]){
  94     const int w= b->width;
  95     int y;
  96     const int qlog= av_clip(s->qlog + b->qlog, 0, QROOT*16);
  97     int qmul= ff_qexp[qlog&(QROOT-1)]<<(qlog>>QSHIFT);
  98     int qadd= (s->qbias*qmul)>>QBIAS_SHIFT;
  99     int new_index = 0;
 100
 101     if(b->ibuf == s->spatial_idwt_buffer || s->qlog == LOSSLESS_QLOG){
 102         qadd= 0;
 103         qmul= 1<<QEXPSHIFT;
 104     }
 105
 106     /* If we are on the second or later slice, restore our index. */
 107     if (start_y != 0)
 108         new_index = save_state[0];
 109
 110
 111     for(y=start_y; y<h; y++){
 112         int x = 0;
 113         int v;
 114         IDWTELEM * line = slice_buffer_get_line(sb, y * b->stride_line + b->buf_y_offset) + b->buf_x_offset;
 115         memset(line, 0, b->width*sizeof(IDWTELEM));
 116         v = b->x_coeff[new_index].coeff;
 117         x = b->x_coeff[new_index++].x;
 118         while(x < w){
 119             register int t= ( (v>>1)*qmul + qadd)>>QEXPSHIFT;
 120             register int u= -(v&1);
 121             line[x] = (t^u) - u;
 122
 123             v = b->x_coeff[new_index].coeff;
 124             x = b->x_coeff[new_index++].x;
 125         }
 126     }
 127
 128     /* Save our variables for the next slice. */
 129     save_state[0] = new_index;
 130
 131     return;
 132 }
 133
 134 static int decode_q_branch(SnowContext *s, int level, int x, int y){
 135     const int w= s->b_width << s->block_max_depth;
 136     const int rem_depth= s->block_max_depth - level;
 137     const int index= (x + y*w) << rem_depth;
 138     int trx= (x+1)<<rem_depth;
 139     const BlockNode *left  = x ? &s->block[index-1] : &null_block;
 140     const BlockNode *top   = y ? &s->block[index-w] : &null_block;
 141     const BlockNode *tl    = y && x ? &s->block[index-w-1] : left;
 142     const BlockNode *tr    = y && trx<w && ((x&1)==0 || level==0) ? &s->block[index-w+(1<<rem_depth)] : tl; //FIXME use lt
 143     int s_context= 2*left->level + 2*top->level + tl->level + tr->level;
 144     int res;
 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 0;
 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             if (s->nb_planes > 2) {
 167                 cb+= get_symbol(&s->c, &s->block_state[64], 1);
 168                 cr+= get_symbol(&s->c, &s->block_state[96], 1);
 169             }
 170         }else{
 171             if(s->ref_frames > 1)
 172                 ref= get_symbol(&s->c, &s->block_state[128 + 1024 + 32*ref_context], 0);
 173             if (ref >= s->ref_frames) {
 174                 av_log(s->avctx, AV_LOG_ERROR, "Invalid ref\n");
 175                 return AVERROR_INVALIDDATA;
 176             }
 177             pred_mv(s, &mx, &my, ref, left, top, tr);
 178             mx+= get_symbol(&s->c, &s->block_state[128 + 32*(mx_context + 16*!!ref)], 1);
 179             my+= get_symbol(&s->c, &s->block_state[128 + 32*(my_context + 16*!!ref)], 1);
 180         }
 181         set_blocks(s, level, x, y, l, cb, cr, mx, my, ref, type);
 182     }else{
 183         if ((res = decode_q_branch(s, level+1, 2*x+0, 2*y+0)) < 0 ||
 184             (res = decode_q_branch(s, level+1, 2*x+1, 2*y+0)) < 0 ||
 185             (res = decode_q_branch(s, level+1, 2*x+0, 2*y+1)) < 0 ||
 186             (res = decode_q_branch(s, level+1, 2*x+1, 2*y+1)) < 0)
 187             return res;
 188     }
 189     return 0;
 190 }
 191
 192 static void dequantize_slice_buffered(SnowContext *s, slice_buffer * sb, SubBand *b, IDWTELEM *src, int stride, int start_y, int end_y){
 193     const int w= b->width;
 194     const int qlog= av_clip(s->qlog + b->qlog, 0, QROOT*16);
 195     const int qmul= ff_qexp[qlog&(QROOT-1)]<<(qlog>>QSHIFT);
 196     const int qadd= (s->qbias*qmul)>>QBIAS_SHIFT;
 197     int x,y;
 198
 199     if(s->qlog == LOSSLESS_QLOG) return;
 200
 201     for(y=start_y; y<end_y; y++){
 202 //        DWTELEM * line = slice_buffer_get_line_from_address(sb, src + (y * stride));
 203         IDWTELEM * line = slice_buffer_get_line(sb, (y * b->stride_line) + b->buf_y_offset) + b->buf_x_offset;
 204         for(x=0; x<w; x++){
 205             int i= line[x];
 206             if(i<0){
 207                 line[x]= -((-i*qmul + qadd)>>(QEXPSHIFT)); //FIXME try different bias
 208             }else if(i>0){
 209                 line[x]=  (( i*qmul + qadd)>>(QEXPSHIFT));
 210             }
 211         }
 212     }
 213 }
 214
 215 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){
 216     const int w= b->width;
 217     int x,y;
 218
 219     IDWTELEM * line=0; // silence silly "could be used without having been initialized" warning
 220     IDWTELEM * prev;
 221
 222     if (start_y != 0)
 223         line = slice_buffer_get_line(sb, ((start_y - 1) * b->stride_line) + b->buf_y_offset) + b->buf_x_offset;
 224
 225     for(y=start_y; y<end_y; y++){
 226         prev = line;
 227 //        line = slice_buffer_get_line_from_address(sb, src + (y * stride));
 228         line = slice_buffer_get_line(sb, (y * b->stride_line) + b->buf_y_offset) + b->buf_x_offset;
 229         for(x=0; x<w; x++){
 230             if(x){
 231                 if(use_median){
 232                     if(y && x+1<w) line[x] += mid_pred(line[x - 1], prev[x], prev[x + 1]);
 233                     else  line[x] += line[x - 1];
 234                 }else{
 235                     if(y) line[x] += mid_pred(line[x - 1], prev[x], line[x - 1] + prev[x] - prev[x - 1]);
 236                     else  line[x] += line[x - 1];
 237                 }
 238             }else{
 239                 if(y) line[x] += prev[x];
 240             }
 241         }
 242     }
 243 }
 244
 245 static void decode_qlogs(SnowContext *s){
 246     int plane_index, level, orientation;
 247
 248     for(plane_index=0; plane_index < s->nb_planes; plane_index++){
 249         for(level=0; level<s->spatial_decomposition_count; level++){
 250             for(orientation=level ? 1:0; orientation<4; orientation++){
 251                 int q;
 252                 if     (plane_index==2) q= s->plane[1].band[level][orientation].qlog;
 253                 else if(orientation==2) q= s->plane[plane_index].band[level][1].qlog;
 254                 else                    q= get_symbol(&s->c, s->header_state, 1);
 255                 s->plane[plane_index].band[level][orientation].qlog= q;
 256             }
 257         }
 258     }
 259 }
 260
 261 #define GET_S(dst, check) \
 262     tmp= get_symbol(&s->c, s->header_state, 0);\
 263     if(!(check)){\
 264         av_log(s->avctx, AV_LOG_ERROR, "Error " #dst " is %d\n", tmp);\
 265         return AVERROR_INVALIDDATA;\
 266     }\
 267     dst= tmp;
 268
 269 static int decode_header(SnowContext *s){
 270     int plane_index, tmp;
 271     uint8_t kstate[32];
 272
 273     memset(kstate, MID_STATE, sizeof(kstate));
 274
 275     s->keyframe= get_rac(&s->c, kstate);
 276     if(s->keyframe || s->always_reset){
 277         ff_snow_reset_contexts(s);
 278         s->spatial_decomposition_type=
 279         s->qlog=
 280         s->qbias=
 281         s->mv_scale=
 282         s->block_max_depth= 0;
 283     }
 284     if(s->keyframe){
 285         GET_S(s->version, tmp <= 0U)
 286         s->always_reset= get_rac(&s->c, s->header_state);
 287         s->temporal_decomposition_type= get_symbol(&s->c, s->header_state, 0);
 288         s->temporal_decomposition_count= get_symbol(&s->c, s->header_state, 0);
 289         GET_S(s->spatial_decomposition_count, 0 < tmp && tmp <= MAX_DECOMPOSITIONS)
 290         s->colorspace_type= get_symbol(&s->c, s->header_state, 0);
 291         if (s->colorspace_type == 1) {
 292             s->avctx->pix_fmt= AV_PIX_FMT_GRAY8;
 293             s->nb_planes = 1;
 294         } else if(s->colorspace_type == 0) {
 295             s->chroma_h_shift= get_symbol(&s->c, s->header_state, 0);
 296             s->chroma_v_shift= get_symbol(&s->c, s->header_state, 0);
 297
 298             if(s->chroma_h_shift == 1 && s->chroma_v_shift==1){
 299                 s->avctx->pix_fmt= AV_PIX_FMT_YUV420P;
 300             }else if(s->chroma_h_shift == 0 && s->chroma_v_shift==0){
 301                 s->avctx->pix_fmt= AV_PIX_FMT_YUV444P;
 302             }else if(s->chroma_h_shift == 2 && s->chroma_v_shift==2){
 303                 s->avctx->pix_fmt= AV_PIX_FMT_YUV410P;
 304             } else {
 305                 av_log(s, AV_LOG_ERROR, "unsupported color subsample mode %d %d\n", s->chroma_h_shift, s->chroma_v_shift);
 306                 s->chroma_h_shift = s->chroma_v_shift = 1;
 307                 s->avctx->pix_fmt= AV_PIX_FMT_YUV420P;
 308                 return AVERROR_INVALIDDATA;
 309             }
 310             s->nb_planes = 3;
 311         } else {
 312             av_log(s, AV_LOG_ERROR, "unsupported color space\n");
 313             s->chroma_h_shift = s->chroma_v_shift = 1;
 314             s->avctx->pix_fmt= AV_PIX_FMT_YUV420P;
 315             return AVERROR_INVALIDDATA;
 316         }
 317
 318
 319         s->spatial_scalability= get_rac(&s->c, s->header_state);
 320 //        s->rate_scalability= get_rac(&s->c, s->header_state);
 321         GET_S(s->max_ref_frames, tmp < (unsigned)MAX_REF_FRAMES)
 322         s->max_ref_frames++;
 323
 324         decode_qlogs(s);
 325     }
 326
 327     if(!s->keyframe){
 328         if(get_rac(&s->c, s->header_state)){
 329             for(plane_index=0; plane_index<FFMIN(s->nb_planes, 2); plane_index++){
 330                 int htaps, i, sum=0;
 331                 Plane *p= &s->plane[plane_index];
 332                 p->diag_mc= get_rac(&s->c, s->header_state);
 333                 htaps= get_symbol(&s->c, s->header_state, 0)*2 + 2;
 334                 if((unsigned)htaps > HTAPS_MAX || htaps==0)
 335                     return AVERROR_INVALIDDATA;
 336                 p->htaps= htaps;
 337                 for(i= htaps/2; i; i--){
 338                     p->hcoeff[i]= get_symbol(&s->c, s->header_state, 0) * (1-2*(i&1));
 339                     sum += p->hcoeff[i];
 340                 }
 341                 p->hcoeff[0]= 32-sum;
 342             }
 343             s->plane[2].diag_mc= s->plane[1].diag_mc;
 344             s->plane[2].htaps  = s->plane[1].htaps;
 345             memcpy(s->plane[2].hcoeff, s->plane[1].hcoeff, sizeof(s->plane[1].hcoeff));
 346         }
 347         if(get_rac(&s->c, s->header_state)){
 348             GET_S(s->spatial_decomposition_count, 0 < tmp && tmp <= MAX_DECOMPOSITIONS)
 349             decode_qlogs(s);
 350         }
 351     }
 352
 353     s->spatial_decomposition_type+= get_symbol(&s->c, s->header_state, 1);
 354     if(s->spatial_decomposition_type > 1U){
 355         av_log(s->avctx, AV_LOG_ERROR, "spatial_decomposition_type %d not supported\n", s->spatial_decomposition_type);
 356         return AVERROR_INVALIDDATA;
 357     }
 358     if(FFMIN(s->avctx-> width>>s->chroma_h_shift,
 359              s->avctx->height>>s->chroma_v_shift) >> (s->spatial_decomposition_count-1) <= 1){
 360         av_log(s->avctx, AV_LOG_ERROR, "spatial_decomposition_count %d too large for size\n", s->spatial_decomposition_count);
 361         return AVERROR_INVALIDDATA;
 362     }
 363
 364
 365     s->qlog           += get_symbol(&s->c, s->header_state, 1);
 366     s->mv_scale       += get_symbol(&s->c, s->header_state, 1);
 367     s->qbias          += get_symbol(&s->c, s->header_state, 1);
 368     s->block_max_depth+= get_symbol(&s->c, s->header_state, 1);
 369     if(s->block_max_depth > 1 || s->block_max_depth < 0){
 370         av_log(s->avctx, AV_LOG_ERROR, "block_max_depth= %d is too large\n", s->block_max_depth);
 371         s->block_max_depth= 0;
 372         return AVERROR_INVALIDDATA;
 373     }
 374
 375     return 0;
 376 }
 377
 378 static av_cold int decode_init(AVCodecContext *avctx)
 379 {
 380     int ret;
 381
 382     if ((ret = ff_snow_common_init(avctx)) < 0) {
 383         ff_snow_common_end(avctx->priv_data);
 384         return ret;
 385     }
 386
 387     return 0;
 388 }
 389
 390 static int decode_blocks(SnowContext *s){
 391     int x, y;
 392     int w= s->b_width;
 393     int h= s->b_height;
 394     int res;
 395
 396     for(y=0; y<h; y++){
 397         for(x=0; x<w; x++){
 398             if ((res = decode_q_branch(s, 0, x, y)) < 0)
 399                 return res;
 400         }
 401     }
 402     return 0;
 403 }
 404
 405 static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame,
 406                         AVPacket *avpkt)
 407 {
 408     const uint8_t *buf = avpkt->data;
 409     int buf_size = avpkt->size;
 410     SnowContext *s = avctx->priv_data;
 411     RangeCoder * const c= &s->c;
 412     int bytes_read;
 413     AVFrame *picture = data;
 414     int level, orientation, plane_index;
 415     int res;
 416
 417     ff_init_range_decoder(c, buf, buf_size);
 418     ff_build_rac_states(c, 0.05*(1LL<<32), 256-8);
 419
 420     s->current_picture->pict_type= AV_PICTURE_TYPE_I; //FIXME I vs. P
 421     if ((res = decode_header(s)) < 0)
 422         return res;
 423     if ((res=ff_snow_common_init_after_header(avctx)) < 0)
 424         return res;
 425
 426     // realloc slice buffer for the case that spatial_decomposition_count changed
 427     ff_slice_buffer_destroy(&s->sb);
 428     if ((res = ff_slice_buffer_init(&s->sb, s->plane[0].height,
 429                                     (MB_SIZE >> s->block_max_depth) +
 430                                     s->spatial_decomposition_count * 11 + 1,
 431                                     s->plane[0].width,
 432                                     s->spatial_idwt_buffer)) < 0)
 433         return res;
 434
 435     for(plane_index=0; plane_index < s->nb_planes; plane_index++){
 436         Plane *p= &s->plane[plane_index];
 437         p->fast_mc= p->diag_mc && p->htaps==6 && p->hcoeff[0]==40
 438                                               && p->hcoeff[1]==-10
 439                                               && p->hcoeff[2]==2;
 440     }
 441
 442     ff_snow_alloc_blocks(s);
 443
 444     if((res = ff_snow_frame_start(s)) < 0)
 445         return res;
 446     //keyframe flag duplication mess FIXME
 447     if(avctx->debug&FF_DEBUG_PICT_INFO)
 448         av_log(avctx, AV_LOG_ERROR,
 449                "keyframe:%d qlog:%d qbias: %d mvscale: %d "
 450                "decomposition_type:%d decomposition_count:%d\n",
 451                s->keyframe, s->qlog, s->qbias, s->mv_scale,
 452                s->spatial_decomposition_type,
 453                s->spatial_decomposition_count
 454               );
 455
 456     if ((res = decode_blocks(s)) < 0)
 457         return res;
 458
 459     for(plane_index=0; plane_index < s->nb_planes; plane_index++){
 460         Plane *p= &s->plane[plane_index];
 461         int w= p->width;
 462         int h= p->height;
 463         int x, y;
 464         int decode_state[MAX_DECOMPOSITIONS][4][1]; /* Stored state info for unpack_coeffs. 1 variable per instance. */
 465
 466         if(s->avctx->debug&2048){
 467             memset(s->spatial_dwt_buffer, 0, sizeof(DWTELEM)*w*h);
 468             predict_plane(s, s->spatial_idwt_buffer, plane_index, 1);
 469
 470             for(y=0; y<h; y++){
 471                 for(x=0; x<w; x++){
 472                     int v= s->current_picture->data[plane_index][y*s->current_picture->linesize[plane_index] + x];
 473                     s->mconly_picture->data[plane_index][y*s->mconly_picture->linesize[plane_index] + x]= v;
 474                 }
 475             }
 476         }
 477
 478         {
 479         for(level=0; level<s->spatial_decomposition_count; level++){
 480             for(orientation=level ? 1 : 0; orientation<4; orientation++){
 481                 SubBand *b= &p->band[level][orientation];
 482                 unpack_coeffs(s, b, b->parent, orientation);
 483             }
 484         }
 485         }
 486
 487         {
 488         const int mb_h= s->b_height << s->block_max_depth;
 489         const int block_size = MB_SIZE >> s->block_max_depth;
 490         const int block_h    = plane_index ? block_size>>s->chroma_v_shift : block_size;
 491         int mb_y;
 492         DWTCompose cs[MAX_DECOMPOSITIONS];
 493         int yd=0, yq=0;
 494         int y;
 495         int end_y;
 496
 497         ff_spatial_idwt_buffered_init(cs, &s->sb, w, h, 1, s->spatial_decomposition_type, s->spatial_decomposition_count);
 498         for(mb_y=0; mb_y<=mb_h; mb_y++){
 499
 500             int slice_starty = block_h*mb_y;
 501             int slice_h = block_h*(mb_y+1);
 502
 503             if (!(s->keyframe || s->avctx->debug&512)){
 504                 slice_starty = FFMAX(0, slice_starty - (block_h >> 1));
 505                 slice_h -= (block_h >> 1);
 506             }
 507
 508             for(level=0; level<s->spatial_decomposition_count; level++){
 509                 for(orientation=level ? 1 : 0; orientation<4; orientation++){
 510                     SubBand *b= &p->band[level][orientation];
 511                     int start_y;
 512                     int end_y;
 513                     int our_mb_start = mb_y;
 514                     int our_mb_end = (mb_y + 1);
 515                     const int extra= 3;
 516                     start_y = (mb_y ? ((block_h * our_mb_start) >> (s->spatial_decomposition_count - level)) + s->spatial_decomposition_count - level + extra: 0);
 517                     end_y = (((block_h * our_mb_end) >> (s->spatial_decomposition_count - level)) + s->spatial_decomposition_count - level + extra);
 518                     if (!(s->keyframe || s->avctx->debug&512)){
 519                         start_y = FFMAX(0, start_y - (block_h >> (1+s->spatial_decomposition_count - level)));
 520                         end_y = FFMAX(0, end_y - (block_h >> (1+s->spatial_decomposition_count - level)));
 521                     }
 522                     start_y = FFMIN(b->height, start_y);
 523                     end_y = FFMIN(b->height, end_y);
 524
 525                     if (start_y != end_y){
 526                         if (orientation == 0){
 527                             SubBand * correlate_band = &p->band[0][0];
 528                             int correlate_end_y = FFMIN(b->height, end_y + 1);
 529                             int correlate_start_y = FFMIN(b->height, (start_y ? start_y + 1 : 0));
 530                             decode_subband_slice_buffered(s, correlate_band, &s->sb, correlate_start_y, correlate_end_y, decode_state[0][0]);
 531                             correlate_slice_buffered(s, &s->sb, correlate_band, correlate_band->ibuf, correlate_band->stride, 1, 0, correlate_start_y, correlate_end_y);
 532                             dequantize_slice_buffered(s, &s->sb, correlate_band, correlate_band->ibuf, correlate_band->stride, start_y, end_y);
 533                         }
 534                         else
 535                             decode_subband_slice_buffered(s, b, &s->sb, start_y, end_y, decode_state[level][orientation]);
 536                     }
 537                 }
 538             }
 539
 540             for(; yd<slice_h; yd+=4){
 541                 ff_spatial_idwt_buffered_slice(&s->dwt, cs, &s->sb, s->temp_idwt_buffer, w, h, 1, s->spatial_decomposition_type, s->spatial_decomposition_count, yd);
 542             }
 543
 544             if(s->qlog == LOSSLESS_QLOG){
 545                 for(; yq<slice_h && yq<h; yq++){
 546                     IDWTELEM * line = slice_buffer_get_line(&s->sb, yq);
 547                     for(x=0; x<w; x++){
 548                         line[x] <<= FRAC_BITS;
 549                     }
 550                 }
 551             }
 552
 553             predict_slice_buffered(s, &s->sb, s->spatial_idwt_buffer, plane_index, 1, mb_y);
 554
 555             y = FFMIN(p->height, slice_starty);
 556             end_y = FFMIN(p->height, slice_h);
 557             while(y < end_y)
 558                 ff_slice_buffer_release(&s->sb, y++);
 559         }
 560
 561         ff_slice_buffer_flush(&s->sb);
 562         }
 563
 564     }
 565
 566     emms_c();
 567
 568     ff_snow_release_buffer(avctx);
 569
 570     if(!(s->avctx->debug&2048))
 571         res = av_frame_ref(picture, s->current_picture);
 572     else
 573         res = av_frame_ref(picture, s->mconly_picture);
 574
 575     if (res < 0)
 576         return res;
 577
 578     *got_frame = 1;
 579
 580     bytes_read= c->bytestream - c->bytestream_start;
 581     if(bytes_read ==0) av_log(s->avctx, AV_LOG_ERROR, "error at end of frame\n"); //FIXME
 582
 583     return bytes_read;
 584 }
 585
 586 static av_cold int decode_end(AVCodecContext *avctx)
 587 {
 588     SnowContext *s = avctx->priv_data;
 589
 590     ff_slice_buffer_destroy(&s->sb);
 591
 592     ff_snow_common_end(s);
 593
 594     return 0;
 595 }
 596
 597 AVCodec ff_snow_decoder = {
 598     .name           = "snow",
 599     .long_name      = NULL_IF_CONFIG_SMALL("Snow"),
 600     .type           = AVMEDIA_TYPE_VIDEO,
 601     .id             = AV_CODEC_ID_SNOW,
 602     .priv_data_size = sizeof(SnowContext),
 603     .init           = decode_init,
 604     .close          = decode_end,
 605     .decode         = decode_frame,
 606     .capabilities   = CODEC_CAP_DR1 /*| CODEC_CAP_DRAW_HORIZ_BAND*/,
 607 };