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1
/*
2
 * H261 decoder
3
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
4
 * Copyright (c) 2004 Maarten Daniels
5
 *
6
 * This file is part of FFmpeg.
7
 *
8
 * FFmpeg is free software; you can redistribute it and/or
9
 * modify it under the terms of the GNU Lesser General Public
10
 * License as published by the Free Software Foundation; either
11
 * version 2.1 of the License, or (at your option) any later version.
12
 *
13
 * FFmpeg is distributed in the hope that it will be useful,
14
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16
 * Lesser General Public License for more details.
17
 *
18
 * You should have received a copy of the GNU Lesser General Public
19
 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21
 */
22

    
23
/**
24
 * @file h261dec.c
25
 * H.261 decoder.
26
 */
27

    
28
#include "dsputil.h"
29
#include "avcodec.h"
30
#include "mpegvideo.h"
31
#include "h261data.h"
32
#include "h261.h"
33

    
34
#define H261_MBA_VLC_BITS 9
35
#define H261_MTYPE_VLC_BITS 6
36
#define H261_MV_VLC_BITS 7
37
#define H261_CBP_VLC_BITS 9
38
#define TCOEFF_VLC_BITS 9
39
#define MBA_STUFFING 33
40
#define MBA_STARTCODE 34
41

    
42
extern uint8_t ff_h261_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
43

    
44
static VLC h261_mba_vlc;
45
static VLC h261_mtype_vlc;
46
static VLC h261_mv_vlc;
47
static VLC h261_cbp_vlc;
48

    
49
static int h261_decode_block(H261Context * h, DCTELEM * block, int n, int coded);
50

    
51
static void h261_decode_init_vlc(H261Context *h){
52
    static int done = 0;
53

    
54
    if(!done){
55
        done = 1;
56
        init_vlc(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
57
                 h261_mba_bits, 1, 1,
58
                 h261_mba_code, 1, 1, 1);
59
        init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
60
                 h261_mtype_bits, 1, 1,
61
                 h261_mtype_code, 1, 1, 1);
62
        init_vlc(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
63
                 &h261_mv_tab[0][1], 2, 1,
64
                 &h261_mv_tab[0][0], 2, 1, 1);
65
        init_vlc(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
66
                 &h261_cbp_tab[0][1], 2, 1,
67
                 &h261_cbp_tab[0][0], 2, 1, 1);
68
        init_rl(&h261_rl_tcoeff, ff_h261_rl_table_store);
69
        init_vlc_rl(&h261_rl_tcoeff, 1);
70
    }
71
}
72

    
73
static int h261_decode_init(AVCodecContext *avctx){
74
    H261Context *h= avctx->priv_data;
75
    MpegEncContext * const s = &h->s;
76

    
77
    // set defaults
78
    MPV_decode_defaults(s);
79
    s->avctx = avctx;
80

    
81
    s->width  = s->avctx->coded_width;
82
    s->height = s->avctx->coded_height;
83
    s->codec_id = s->avctx->codec->id;
84

    
85
    s->out_format = FMT_H261;
86
    s->low_delay= 1;
87
    avctx->pix_fmt= PIX_FMT_YUV420P;
88

    
89
    s->codec_id= avctx->codec->id;
90

    
91
    h261_decode_init_vlc(h);
92

    
93
    h->gob_start_code_skipped = 0;
94

    
95
    return 0;
96
}
97

    
98
/**
99
 * decodes the group of blocks header or slice header.
100
 * @return <0 if an error occured
101
 */
102
static int h261_decode_gob_header(H261Context *h){
103
    unsigned int val;
104
    MpegEncContext * const s = &h->s;
105

    
106
    if ( !h->gob_start_code_skipped ){
107
        /* Check for GOB Start Code */
108
        val = show_bits(&s->gb, 15);
109
        if(val)
110
            return -1;
111

    
112
        /* We have a GBSC */
113
        skip_bits(&s->gb, 16);
114
    }
115

    
116
    h->gob_start_code_skipped = 0;
117

    
118
    h->gob_number = get_bits(&s->gb, 4); /* GN */
119
    s->qscale = get_bits(&s->gb, 5); /* GQUANT */
120

    
121
    /* Check if gob_number is valid */
122
    if (s->mb_height==18){ //cif
123
        if ((h->gob_number<=0) || (h->gob_number>12))
124
            return -1;
125
    }
126
    else{ //qcif
127
        if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
128
            return -1;
129
    }
130

    
131
    /* GEI */
132
    while (get_bits1(&s->gb) != 0) {
133
        skip_bits(&s->gb, 8);
134
    }
135

    
136
    if(s->qscale==0)
137
        return -1;
138

    
139
    // For the first transmitted macroblock in a GOB, MBA is the absolute address. For
140
    // subsequent macroblocks, MBA is the difference between the absolute addresses of
141
    // the macroblock and the last transmitted macroblock.
142
    h->current_mba = 0;
143
    h->mba_diff = 0;
144

    
145
    return 0;
146
}
147

    
148
/**
149
 * decodes the group of blocks / video packet header.
150
 * @return <0 if no resync found
151
 */
152
static int ff_h261_resync(H261Context *h){
153
    MpegEncContext * const s = &h->s;
154
    int left, ret;
155

    
156
    if ( h->gob_start_code_skipped ){
157
        ret= h261_decode_gob_header(h);
158
        if(ret>=0)
159
            return 0;
160
    }
161
    else{
162
        if(show_bits(&s->gb, 15)==0){
163
            ret= h261_decode_gob_header(h);
164
            if(ret>=0)
165
                return 0;
166
        }
167
        //ok, its not where its supposed to be ...
168
        s->gb= s->last_resync_gb;
169
        align_get_bits(&s->gb);
170
        left= s->gb.size_in_bits - get_bits_count(&s->gb);
171

    
172
        for(;left>15+1+4+5; left-=8){
173
            if(show_bits(&s->gb, 15)==0){
174
                GetBitContext bak= s->gb;
175

    
176
                ret= h261_decode_gob_header(h);
177
                if(ret>=0)
178
                    return 0;
179

    
180
                s->gb= bak;
181
            }
182
            skip_bits(&s->gb, 8);
183
        }
184
    }
185

    
186
    return -1;
187
}
188

    
189
/**
190
 * decodes skipped macroblocks
191
 * @return 0
192
 */
193
static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
194
{
195
    MpegEncContext * const s = &h->s;
196
    int i;
197

    
198
    s->mb_intra = 0;
199

    
200
    for(i=mba1; i<mba2; i++){
201
        int j, xy;
202

    
203
        s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
204
        s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
205
        xy = s->mb_x + s->mb_y * s->mb_stride;
206
        ff_init_block_index(s);
207
        ff_update_block_index(s);
208

    
209
        for(j=0;j<6;j++)
210
            s->block_last_index[j] = -1;
211

    
212
        s->mv_dir = MV_DIR_FORWARD;
213
        s->mv_type = MV_TYPE_16X16;
214
        s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
215
        s->mv[0][0][0] = 0;
216
        s->mv[0][0][1] = 0;
217
        s->mb_skipped = 1;
218
        h->mtype &= ~MB_TYPE_H261_FIL;
219

    
220
        MPV_decode_mb(s, s->block);
221
    }
222

    
223
    return 0;
224
}
225

    
226
static int decode_mv_component(GetBitContext *gb, int v){
227
    int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
228

    
229
    /* check if mv_diff is valid */
230
    if ( mv_diff < 0 )
231
        return v;
232

    
233
    mv_diff = mvmap[mv_diff];
234

    
235
    if(mv_diff && !get_bits1(gb))
236
        mv_diff= -mv_diff;
237

    
238
    v += mv_diff;
239
    if     (v <=-16) v+= 32;
240
    else if(v >= 16) v-= 32;
241

    
242
    return v;
243
}
244

    
245
static int h261_decode_mb(H261Context *h){
246
    MpegEncContext * const s = &h->s;
247
    int i, cbp, xy;
248

    
249
    cbp = 63;
250
    // Read mba
251
    do{
252
        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
253

    
254
        /* Check for slice end */
255
        /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
256
        if (h->mba_diff == MBA_STARTCODE){ // start code
257
            h->gob_start_code_skipped = 1;
258
            return SLICE_END;
259
        }
260
    }
261
    while( h->mba_diff == MBA_STUFFING ); // stuffing
262

    
263
    if ( h->mba_diff < 0 ){
264
        if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
265
            return SLICE_END;
266

    
267
        av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
268
        return SLICE_ERROR;
269
    }
270

    
271
    h->mba_diff += 1;
272
    h->current_mba += h->mba_diff;
273

    
274
    if ( h->current_mba > MBA_STUFFING )
275
        return SLICE_ERROR;
276

    
277
    s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
278
    s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
279
    xy = s->mb_x + s->mb_y * s->mb_stride;
280
    ff_init_block_index(s);
281
    ff_update_block_index(s);
282

    
283
    // Read mtype
284
    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
285
    h->mtype = h261_mtype_map[h->mtype];
286

    
287
    // Read mquant
288
    if ( IS_QUANT ( h->mtype ) ){
289
        ff_set_qscale(s, get_bits(&s->gb, 5));
290
    }
291

    
292
    s->mb_intra = IS_INTRA4x4(h->mtype);
293

    
294
    // Read mv
295
    if ( IS_16X16 ( h->mtype ) ){
296
        // Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the
297
        // vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the
298
        // following three situations:
299
        // 1) evaluating MVD for macroblocks 1, 12 and 23;
300
        // 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
301
        // 3) MTYPE of the previous macroblock was not MC.
302
        if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) ||
303
             ( h->mba_diff != 1))
304
        {
305
            h->current_mv_x = 0;
306
            h->current_mv_y = 0;
307
        }
308

    
309
        h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
310
        h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
311
    }else{
312
        h->current_mv_x = 0;
313
        h->current_mv_y = 0;
314
    }
315

    
316
    // Read cbp
317
    if ( HAS_CBP( h->mtype ) ){
318
        cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
319
    }
320

    
321
    if(s->mb_intra){
322
        s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
323
        goto intra;
324
    }
325

    
326
    //set motion vectors
327
    s->mv_dir = MV_DIR_FORWARD;
328
    s->mv_type = MV_TYPE_16X16;
329
    s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
330
    s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation
331
    s->mv[0][0][1] = h->current_mv_y * 2;
332

    
333
intra:
334
    /* decode each block */
335
    if(s->mb_intra || HAS_CBP(h->mtype)){
336
        s->dsp.clear_blocks(s->block[0]);
337
        for (i = 0; i < 6; i++) {
338
            if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
339
                return SLICE_ERROR;
340
            }
341
            cbp+=cbp;
342
        }
343
    }else{
344
        for (i = 0; i < 6; i++)
345
            s->block_last_index[i]= -1;
346
    }
347

    
348
    MPV_decode_mb(s, s->block);
349

    
350
    return SLICE_OK;
351
}
352

    
353
/**
354
 * decodes a macroblock
355
 * @return <0 if an error occured
356
 */
357
static int h261_decode_block(H261Context * h, DCTELEM * block,
358
                             int n, int coded)
359
{
360
    MpegEncContext * const s = &h->s;
361
    int code, level, i, j, run;
362
    RLTable *rl = &h261_rl_tcoeff;
363
    const uint8_t *scan_table;
364

    
365
    // For the variable length encoding there are two code tables, one being used for
366
    // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
367
    // for all other LEVELs except the first one in INTRA blocks which is fixed length
368
    // coded with 8 bits.
369
    // NOTE: the two code tables only differ in one VLC so we handle that manually.
370
    scan_table = s->intra_scantable.permutated;
371
    if (s->mb_intra){
372
        /* DC coef */
373
        level = get_bits(&s->gb, 8);
374
        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
375
        if((level&0x7F) == 0){
376
            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
377
            return -1;
378
        }
379
        // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
380
        if (level == 255)
381
            level = 128;
382
        block[0] = level;
383
        i = 1;
384
    }else if(coded){
385
        // Run  Level   Code
386
        // EOB                  Not possible for first level when cbp is available (that's why the table is different)
387
        // 0    1               1s
388
        // *    *               0*
389
        int check = show_bits(&s->gb, 2);
390
        i = 0;
391
        if ( check & 0x2 ){
392
            skip_bits(&s->gb, 2);
393
            block[0] = ( check & 0x1 ) ? -1 : 1;
394
            i = 1;
395
        }
396
    }else{
397
        i = 0;
398
    }
399
    if(!coded){
400
        s->block_last_index[n] = i - 1;
401
        return 0;
402
    }
403
    for(;;){
404
        code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
405
        if (code < 0){
406
            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
407
            return -1;
408
        }
409
        if (code == rl->n) {
410
            /* escape */
411
            // The remaining combinations of (run, level) are encoded with a 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits level.
412
            run = get_bits(&s->gb, 6);
413
            level = get_sbits(&s->gb, 8);
414
        }else if(code == 0){
415
            break;
416
        }else{
417
            run = rl->table_run[code];
418
            level = rl->table_level[code];
419
            if (get_bits1(&s->gb))
420
                level = -level;
421
        }
422
        i += run;
423
        if (i >= 64){
424
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
425
            return -1;
426
        }
427
        j = scan_table[i];
428
        block[j] = level;
429
        i++;
430
    }
431
    s->block_last_index[n] = i-1;
432
    return 0;
433
}
434

    
435
/**
436
 * decodes the H261 picture header.
437
 * @return <0 if no startcode found
438
 */
439
static int h261_decode_picture_header(H261Context *h){
440
    MpegEncContext * const s = &h->s;
441
    int format, i;
442
    uint32_t startcode= 0;
443

    
444
    for(i= s->gb.size_in_bits - get_bits_count(&s->gb); i>24; i-=1){
445
        startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
446

    
447
        if(startcode == 0x10)
448
            break;
449
    }
450

    
451
    if (startcode != 0x10){
452
        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
453
        return -1;
454
    }
455

    
456
    /* temporal reference */
457
    i= get_bits(&s->gb, 5); /* picture timestamp */
458
    if(i < (s->picture_number&31))
459
        i += 32;
460
    s->picture_number = (s->picture_number&~31) + i;
461

    
462
    s->avctx->time_base= (AVRational){1001, 30000};
463
    s->current_picture.pts= s->picture_number;
464

    
465

    
466
    /* PTYPE starts here */
467
    skip_bits1(&s->gb); /* split screen off */
468
    skip_bits1(&s->gb); /* camera  off */
469
    skip_bits1(&s->gb); /* freeze picture release off */
470

    
471
    format = get_bits1(&s->gb);
472

    
473
    //only 2 formats possible
474
    if (format == 0){//QCIF
475
        s->width = 176;
476
        s->height = 144;
477
        s->mb_width = 11;
478
        s->mb_height = 9;
479
    }else{//CIF
480
        s->width = 352;
481
        s->height = 288;
482
        s->mb_width = 22;
483
        s->mb_height = 18;
484
    }
485

    
486
    s->mb_num = s->mb_width * s->mb_height;
487

    
488
    skip_bits1(&s->gb); /* still image mode off */
489
    skip_bits1(&s->gb); /* Reserved */
490

    
491
    /* PEI */
492
    while (get_bits1(&s->gb) != 0){
493
        skip_bits(&s->gb, 8);
494
    }
495

    
496
    // h261 has no I-FRAMES, but if we pass I_TYPE for the first frame, the codec crashes if it does
497
    // not contain all I-blocks (e.g. when a packet is lost)
498
    s->pict_type = P_TYPE;
499

    
500
    h->gob_number = 0;
501
    return 0;
502
}
503

    
504
static int h261_decode_gob(H261Context *h){
505
    MpegEncContext * const s = &h->s;
506

    
507
    ff_set_qscale(s, s->qscale);
508

    
509
    /* decode mb's */
510
    while(h->current_mba <= MBA_STUFFING)
511
    {
512
        int ret;
513
        /* DCT & quantize */
514
        ret= h261_decode_mb(h);
515
        if(ret<0){
516
            if(ret==SLICE_END){
517
                h261_decode_mb_skipped(h, h->current_mba, 33);
518
                return 0;
519
            }
520
            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
521
            return -1;
522
        }
523

    
524
        h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
525
    }
526

    
527
    return -1;
528
}
529

    
530
/**
531
 * returns the number of bytes consumed for building the current frame
532
 */
533
static int get_consumed_bytes(MpegEncContext *s, int buf_size){
534
    int pos= get_bits_count(&s->gb)>>3;
535
    if(pos==0) pos=1; //avoid infinite loops (i doubt that is needed but ...)
536
    if(pos+10>buf_size) pos=buf_size; // oops ;)
537

    
538
    return pos;
539
}
540

    
541
static int h261_decode_frame(AVCodecContext *avctx,
542
                             void *data, int *data_size,
543
                             uint8_t *buf, int buf_size)
544
{
545
    H261Context *h= avctx->priv_data;
546
    MpegEncContext *s = &h->s;
547
    int ret;
548
    AVFrame *pict = data;
549

    
550
#ifdef DEBUG
551
    av_log(avctx, AV_LOG_DEBUG, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
552
    av_log(avctx, AV_LOG_DEBUG, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
553
#endif
554
    s->flags= avctx->flags;
555
    s->flags2= avctx->flags2;
556

    
557
    h->gob_start_code_skipped=0;
558

    
559
retry:
560

    
561
    init_get_bits(&s->gb, buf, buf_size*8);
562

    
563
    if(!s->context_initialized){
564
        if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
565
            return -1;
566
    }
567

    
568
    //we need to set current_picture_ptr before reading the header, otherwise we cannot store anyting im there
569
    if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
570
        int i= ff_find_unused_picture(s, 0);
571
        s->current_picture_ptr= &s->picture[i];
572
    }
573

    
574
    ret = h261_decode_picture_header(h);
575

    
576
    /* skip if the header was thrashed */
577
    if (ret < 0){
578
        av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
579
        return -1;
580
    }
581

    
582
    if (s->width != avctx->coded_width || s->height != avctx->coded_height){
583
        ParseContext pc= s->parse_context; //FIXME move this demuxing hack to libavformat
584
        s->parse_context.buffer=0;
585
        MPV_common_end(s);
586
        s->parse_context= pc;
587
    }
588
    if (!s->context_initialized) {
589
        avcodec_set_dimensions(avctx, s->width, s->height);
590

    
591
        goto retry;
592
    }
593

    
594
    // for hurry_up==5
595
    s->current_picture.pict_type= s->pict_type;
596
    s->current_picture.key_frame= s->pict_type == I_TYPE;
597

    
598
    /* skip everything if we are in a hurry>=5 */
599
    if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
600
    if(  (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==B_TYPE)
601
       ||(avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=I_TYPE)
602
       || avctx->skip_frame >= AVDISCARD_ALL)
603
        return get_consumed_bytes(s, buf_size);
604

    
605
    if(MPV_frame_start(s, avctx) < 0)
606
        return -1;
607

    
608
    ff_er_frame_start(s);
609

    
610
    /* decode each macroblock */
611
    s->mb_x=0;
612
    s->mb_y=0;
613

    
614
    while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
615
        if(ff_h261_resync(h)<0)
616
            break;
617
        h261_decode_gob(h);
618
    }
619
    MPV_frame_end(s);
620

    
621
assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
622
assert(s->current_picture.pict_type == s->pict_type);
623
    *pict= *(AVFrame*)s->current_picture_ptr;
624
    ff_print_debug_info(s, pict);
625

    
626
    *data_size = sizeof(AVFrame);
627

    
628
    return get_consumed_bytes(s, buf_size);
629
}
630

    
631
static int h261_decode_end(AVCodecContext *avctx)
632
{
633
    H261Context *h= avctx->priv_data;
634
    MpegEncContext *s = &h->s;
635

    
636
    MPV_common_end(s);
637
    return 0;
638
}
639

    
640
AVCodec h261_decoder = {
641
    "h261",
642
    CODEC_TYPE_VIDEO,
643
    CODEC_ID_H261,
644
    sizeof(H261Context),
645
    h261_decode_init,
646
    NULL,
647
    h261_decode_end,
648
    h261_decode_frame,
649
    CODEC_CAP_DR1,
650
};