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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 Libav.
7
 *
8
 * Libav 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
 *
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 * Libav 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
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; 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
25
 * H.261 decoder.
26
 */
27

    
28
#include "dsputil.h"
29
#include "avcodec.h"
30
#include "mpegvideo.h"
31
#include "h263.h"
32
#include "h261.h"
33
#include "h261data.h"
34

    
35
#define H261_MBA_VLC_BITS 9
36
#define H261_MTYPE_VLC_BITS 6
37
#define H261_MV_VLC_BITS 7
38
#define H261_CBP_VLC_BITS 9
39
#define TCOEFF_VLC_BITS 9
40
#define MBA_STUFFING 33
41
#define MBA_STARTCODE 34
42

    
43
extern uint8_t ff_h261_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
44

    
45
static VLC h261_mba_vlc;
46
static VLC h261_mtype_vlc;
47
static VLC h261_mv_vlc;
48
static VLC h261_cbp_vlc;
49

    
50
static int h261_decode_block(H261Context * h, DCTELEM * block, int n, int coded);
51

    
52
static av_cold void h261_decode_init_vlc(H261Context *h){
53
    static int done = 0;
54

    
55
    if(!done){
56
        done = 1;
57
        INIT_VLC_STATIC(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
58
                 h261_mba_bits, 1, 1,
59
                 h261_mba_code, 1, 1, 662);
60
        INIT_VLC_STATIC(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
61
                 h261_mtype_bits, 1, 1,
62
                 h261_mtype_code, 1, 1, 80);
63
        INIT_VLC_STATIC(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
64
                 &h261_mv_tab[0][1], 2, 1,
65
                 &h261_mv_tab[0][0], 2, 1, 144);
66
        INIT_VLC_STATIC(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
67
                 &h261_cbp_tab[0][1], 2, 1,
68
                 &h261_cbp_tab[0][0], 2, 1, 512);
69
        init_rl(&h261_rl_tcoeff, ff_h261_rl_table_store);
70
        INIT_VLC_RL(h261_rl_tcoeff, 552);
71
    }
72
}
73

    
74
static av_cold int h261_decode_init(AVCodecContext *avctx){
75
    H261Context *h= avctx->priv_data;
76
    MpegEncContext * const s = &h->s;
77

    
78
    // set defaults
79
    MPV_decode_defaults(s);
80
    s->avctx = avctx;
81

    
82
    s->width  = s->avctx->coded_width;
83
    s->height = s->avctx->coded_height;
84
    s->codec_id = s->avctx->codec->id;
85

    
86
    s->out_format = FMT_H261;
87
    s->low_delay= 1;
88
    avctx->pix_fmt= PIX_FMT_YUV420P;
89

    
90
    s->codec_id= avctx->codec->id;
91

    
92
    h261_decode_init_vlc(h);
93

    
94
    h->gob_start_code_skipped = 0;
95

    
96
    return 0;
97
}
98

    
99
/**
100
 * decodes the group of blocks header or slice header.
101
 * @return <0 if an error occurred
102
 */
103
static int h261_decode_gob_header(H261Context *h){
104
    unsigned int val;
105
    MpegEncContext * const s = &h->s;
106

    
107
    if ( !h->gob_start_code_skipped ){
108
        /* Check for GOB Start Code */
109
        val = show_bits(&s->gb, 15);
110
        if(val)
111
            return -1;
112

    
113
        /* We have a GBSC */
114
        skip_bits(&s->gb, 16);
115
    }
116

    
117
    h->gob_start_code_skipped = 0;
118

    
119
    h->gob_number = get_bits(&s->gb, 4); /* GN */
120
    s->qscale = get_bits(&s->gb, 5); /* GQUANT */
121

    
122
    /* Check if gob_number is valid */
123
    if (s->mb_height==18){ //cif
124
        if ((h->gob_number<=0) || (h->gob_number>12))
125
            return -1;
126
    }
127
    else{ //qcif
128
        if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
129
            return -1;
130
    }
131

    
132
    /* GEI */
133
    while (get_bits1(&s->gb) != 0) {
134
        skip_bits(&s->gb, 8);
135
    }
136

    
137
    if(s->qscale==0) {
138
        av_log(s->avctx, AV_LOG_ERROR, "qscale has forbidden 0 value\n");
139
        if (s->avctx->error_recognition >= FF_ER_COMPLIANT)
140
            return -1;
141
    }
142

    
143
    // For the first transmitted macroblock in a GOB, MBA is the absolute address. For
144
    // subsequent macroblocks, MBA is the difference between the absolute addresses of
145
    // the macroblock and the last transmitted macroblock.
146
    h->current_mba = 0;
147
    h->mba_diff = 0;
148

    
149
    return 0;
150
}
151

    
152
/**
153
 * decodes the group of blocks / video packet header.
154
 * @return <0 if no resync found
155
 */
156
static int ff_h261_resync(H261Context *h){
157
    MpegEncContext * const s = &h->s;
158
    int left, ret;
159

    
160
    if ( h->gob_start_code_skipped ){
161
        ret= h261_decode_gob_header(h);
162
        if(ret>=0)
163
            return 0;
164
    }
165
    else{
166
        if(show_bits(&s->gb, 15)==0){
167
            ret= h261_decode_gob_header(h);
168
            if(ret>=0)
169
                return 0;
170
        }
171
        //OK, it is not where it is supposed to be ...
172
        s->gb= s->last_resync_gb;
173
        align_get_bits(&s->gb);
174
        left= get_bits_left(&s->gb);
175

    
176
        for(;left>15+1+4+5; left-=8){
177
            if(show_bits(&s->gb, 15)==0){
178
                GetBitContext bak= s->gb;
179

    
180
                ret= h261_decode_gob_header(h);
181
                if(ret>=0)
182
                    return 0;
183

    
184
                s->gb= bak;
185
            }
186
            skip_bits(&s->gb, 8);
187
        }
188
    }
189

    
190
    return -1;
191
}
192

    
193
/**
194
 * decodes skipped macroblocks
195
 * @return 0
196
 */
197
static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
198
{
199
    MpegEncContext * const s = &h->s;
200
    int i;
201

    
202
    s->mb_intra = 0;
203

    
204
    for(i=mba1; i<mba2; i++){
205
        int j, xy;
206

    
207
        s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
208
        s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
209
        xy = s->mb_x + s->mb_y * s->mb_stride;
210
        ff_init_block_index(s);
211
        ff_update_block_index(s);
212

    
213
        for(j=0;j<6;j++)
214
            s->block_last_index[j] = -1;
215

    
216
        s->mv_dir = MV_DIR_FORWARD;
217
        s->mv_type = MV_TYPE_16X16;
218
        s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
219
        s->mv[0][0][0] = 0;
220
        s->mv[0][0][1] = 0;
221
        s->mb_skipped = 1;
222
        h->mtype &= ~MB_TYPE_H261_FIL;
223

    
224
        MPV_decode_mb(s, s->block);
225
    }
226

    
227
    return 0;
228
}
229

    
230
static int decode_mv_component(GetBitContext *gb, int v){
231
    int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
232

    
233
    /* check if mv_diff is valid */
234
    if ( mv_diff < 0 )
235
        return v;
236

    
237
    mv_diff = mvmap[mv_diff];
238

    
239
    if(mv_diff && !get_bits1(gb))
240
        mv_diff= -mv_diff;
241

    
242
    v += mv_diff;
243
    if     (v <=-16) v+= 32;
244
    else if(v >= 16) v-= 32;
245

    
246
    return v;
247
}
248

    
249
static int h261_decode_mb(H261Context *h){
250
    MpegEncContext * const s = &h->s;
251
    int i, cbp, xy;
252

    
253
    cbp = 63;
254
    // Read mba
255
    do{
256
        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
257

    
258
        /* Check for slice end */
259
        /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
260
        if (h->mba_diff == MBA_STARTCODE){ // start code
261
            h->gob_start_code_skipped = 1;
262
            return SLICE_END;
263
        }
264
    }
265
    while( h->mba_diff == MBA_STUFFING ); // stuffing
266

    
267
    if ( h->mba_diff < 0 ){
268
        if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
269
            return SLICE_END;
270

    
271
        av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
272
        return SLICE_ERROR;
273
    }
274

    
275
    h->mba_diff += 1;
276
    h->current_mba += h->mba_diff;
277

    
278
    if ( h->current_mba > MBA_STUFFING )
279
        return SLICE_ERROR;
280

    
281
    s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
282
    s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
283
    xy = s->mb_x + s->mb_y * s->mb_stride;
284
    ff_init_block_index(s);
285
    ff_update_block_index(s);
286

    
287
    // Read mtype
288
    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
289
    h->mtype = h261_mtype_map[h->mtype];
290

    
291
    // Read mquant
292
    if ( IS_QUANT ( h->mtype ) ){
293
        ff_set_qscale(s, get_bits(&s->gb, 5));
294
    }
295

    
296
    s->mb_intra = IS_INTRA4x4(h->mtype);
297

    
298
    // Read mv
299
    if ( IS_16X16 ( h->mtype ) ){
300
        // Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the
301
        // vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the
302
        // following three situations:
303
        // 1) evaluating MVD for macroblocks 1, 12 and 23;
304
        // 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
305
        // 3) MTYPE of the previous macroblock was not MC.
306
        if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) ||
307
             ( h->mba_diff != 1))
308
        {
309
            h->current_mv_x = 0;
310
            h->current_mv_y = 0;
311
        }
312

    
313
        h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
314
        h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
315
    }else{
316
        h->current_mv_x = 0;
317
        h->current_mv_y = 0;
318
    }
319

    
320
    // Read cbp
321
    if ( HAS_CBP( h->mtype ) ){
322
        cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
323
    }
324

    
325
    if(s->mb_intra){
326
        s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
327
        goto intra;
328
    }
329

    
330
    //set motion vectors
331
    s->mv_dir = MV_DIR_FORWARD;
332
    s->mv_type = MV_TYPE_16X16;
333
    s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
334
    s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation
335
    s->mv[0][0][1] = h->current_mv_y * 2;
336

    
337
intra:
338
    /* decode each block */
339
    if(s->mb_intra || HAS_CBP(h->mtype)){
340
        s->dsp.clear_blocks(s->block[0]);
341
        for (i = 0; i < 6; i++) {
342
            if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
343
                return SLICE_ERROR;
344
            }
345
            cbp+=cbp;
346
        }
347
    }else{
348
        for (i = 0; i < 6; i++)
349
            s->block_last_index[i]= -1;
350
    }
351

    
352
    MPV_decode_mb(s, s->block);
353

    
354
    return SLICE_OK;
355
}
356

    
357
/**
358
 * decodes a macroblock
359
 * @return <0 if an error occurred
360
 */
361
static int h261_decode_block(H261Context * h, DCTELEM * block,
362
                             int n, int coded)
363
{
364
    MpegEncContext * const s = &h->s;
365
    int code, level, i, j, run;
366
    RLTable *rl = &h261_rl_tcoeff;
367
    const uint8_t *scan_table;
368

    
369
    // For the variable length encoding there are two code tables, one being used for
370
    // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
371
    // for all other LEVELs except the first one in INTRA blocks which is fixed length
372
    // coded with 8 bits.
373
    // NOTE: the two code tables only differ in one VLC so we handle that manually.
374
    scan_table = s->intra_scantable.permutated;
375
    if (s->mb_intra){
376
        /* DC coef */
377
        level = get_bits(&s->gb, 8);
378
        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
379
        if((level&0x7F) == 0){
380
            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
381
            return -1;
382
        }
383
        // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
384
        if (level == 255)
385
            level = 128;
386
        block[0] = level;
387
        i = 1;
388
    }else if(coded){
389
        // Run  Level   Code
390
        // EOB                  Not possible for first level when cbp is available (that's why the table is different)
391
        // 0    1               1s
392
        // *    *               0*
393
        int check = show_bits(&s->gb, 2);
394
        i = 0;
395
        if ( check & 0x2 ){
396
            skip_bits(&s->gb, 2);
397
            block[0] = ( check & 0x1 ) ? -1 : 1;
398
            i = 1;
399
        }
400
    }else{
401
        i = 0;
402
    }
403
    if(!coded){
404
        s->block_last_index[n] = i - 1;
405
        return 0;
406
    }
407
    for(;;){
408
        code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
409
        if (code < 0){
410
            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
411
            return -1;
412
        }
413
        if (code == rl->n) {
414
            /* escape */
415
            // 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.
416
            run = get_bits(&s->gb, 6);
417
            level = get_sbits(&s->gb, 8);
418
        }else if(code == 0){
419
            break;
420
        }else{
421
            run = rl->table_run[code];
422
            level = rl->table_level[code];
423
            if (get_bits1(&s->gb))
424
                level = -level;
425
        }
426
        i += run;
427
        if (i >= 64){
428
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
429
            return -1;
430
        }
431
        j = scan_table[i];
432
        block[j] = level;
433
        i++;
434
    }
435
    s->block_last_index[n] = i-1;
436
    return 0;
437
}
438

    
439
/**
440
 * decodes the H261 picture header.
441
 * @return <0 if no startcode found
442
 */
443
static int h261_decode_picture_header(H261Context *h){
444
    MpegEncContext * const s = &h->s;
445
    int format, i;
446
    uint32_t startcode= 0;
447

    
448
    for(i= get_bits_left(&s->gb); i>24; i-=1){
449
        startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
450

    
451
        if(startcode == 0x10)
452
            break;
453
    }
454

    
455
    if (startcode != 0x10){
456
        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
457
        return -1;
458
    }
459

    
460
    /* temporal reference */
461
    i= get_bits(&s->gb, 5); /* picture timestamp */
462
    if(i < (s->picture_number&31))
463
        i += 32;
464
    s->picture_number = (s->picture_number&~31) + i;
465

    
466
    s->avctx->time_base= (AVRational){1001, 30000};
467
    s->current_picture.pts= s->picture_number;
468

    
469

    
470
    /* PTYPE starts here */
471
    skip_bits1(&s->gb); /* split screen off */
472
    skip_bits1(&s->gb); /* camera  off */
473
    skip_bits1(&s->gb); /* freeze picture release off */
474

    
475
    format = get_bits1(&s->gb);
476

    
477
    //only 2 formats possible
478
    if (format == 0){//QCIF
479
        s->width = 176;
480
        s->height = 144;
481
        s->mb_width = 11;
482
        s->mb_height = 9;
483
    }else{//CIF
484
        s->width = 352;
485
        s->height = 288;
486
        s->mb_width = 22;
487
        s->mb_height = 18;
488
    }
489

    
490
    s->mb_num = s->mb_width * s->mb_height;
491

    
492
    skip_bits1(&s->gb); /* still image mode off */
493
    skip_bits1(&s->gb); /* Reserved */
494

    
495
    /* PEI */
496
    while (get_bits1(&s->gb) != 0){
497
        skip_bits(&s->gb, 8);
498
    }
499

    
500
    // h261 has no I-FRAMES, but if we pass FF_I_TYPE for the first frame, the codec crashes if it does
501
    // not contain all I-blocks (e.g. when a packet is lost)
502
    s->pict_type = FF_P_TYPE;
503

    
504
    h->gob_number = 0;
505
    return 0;
506
}
507

    
508
static int h261_decode_gob(H261Context *h){
509
    MpegEncContext * const s = &h->s;
510

    
511
    ff_set_qscale(s, s->qscale);
512

    
513
    /* decode mb's */
514
    while(h->current_mba <= MBA_STUFFING)
515
    {
516
        int ret;
517
        /* DCT & quantize */
518
        ret= h261_decode_mb(h);
519
        if(ret<0){
520
            if(ret==SLICE_END){
521
                h261_decode_mb_skipped(h, h->current_mba, 33);
522
                return 0;
523
            }
524
            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
525
            return -1;
526
        }
527

    
528
        h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
529
    }
530

    
531
    return -1;
532
}
533

    
534
/**
535
 * returns the number of bytes consumed for building the current frame
536
 */
537
static int get_consumed_bytes(MpegEncContext *s, int buf_size){
538
    int pos= get_bits_count(&s->gb)>>3;
539
    if(pos==0) pos=1; //avoid infinite loops (i doubt that is needed but ...)
540
    if(pos+10>buf_size) pos=buf_size; // oops ;)
541

    
542
    return pos;
543
}
544

    
545
static int h261_decode_frame(AVCodecContext *avctx,
546
                             void *data, int *data_size,
547
                             AVPacket *avpkt)
548
{
549
    const uint8_t *buf = avpkt->data;
550
    int buf_size = avpkt->size;
551
    H261Context *h= avctx->priv_data;
552
    MpegEncContext *s = &h->s;
553
    int ret;
554
    AVFrame *pict = data;
555

    
556
    av_dlog(avctx, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
557
    av_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
558
    s->flags= avctx->flags;
559
    s->flags2= avctx->flags2;
560

    
561
    h->gob_start_code_skipped=0;
562

    
563
retry:
564

    
565
    init_get_bits(&s->gb, buf, buf_size*8);
566

    
567
    if(!s->context_initialized){
568
        if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
569
            return -1;
570
    }
571

    
572
    //we need to set current_picture_ptr before reading the header, otherwise we cannot store anyting im there
573
    if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
574
        int i= ff_find_unused_picture(s, 0);
575
        s->current_picture_ptr= &s->picture[i];
576
    }
577

    
578
    ret = h261_decode_picture_header(h);
579

    
580
    /* skip if the header was thrashed */
581
    if (ret < 0){
582
        av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
583
        return -1;
584
    }
585

    
586
    if (s->width != avctx->coded_width || s->height != avctx->coded_height){
587
        ParseContext pc= s->parse_context; //FIXME move this demuxing hack to libavformat
588
        s->parse_context.buffer=0;
589
        MPV_common_end(s);
590
        s->parse_context= pc;
591
    }
592
    if (!s->context_initialized) {
593
        avcodec_set_dimensions(avctx, s->width, s->height);
594

    
595
        goto retry;
596
    }
597

    
598
    // for skipping the frame
599
    s->current_picture.pict_type= s->pict_type;
600
    s->current_picture.key_frame= s->pict_type == FF_I_TYPE;
601

    
602
#if FF_API_HURRY_UP
603
    /* skip everything if we are in a hurry>=5 */
604
    if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
605
#endif
606
    if(  (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==FF_B_TYPE)
607
       ||(avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=FF_I_TYPE)
608
       || avctx->skip_frame >= AVDISCARD_ALL)
609
        return get_consumed_bytes(s, buf_size);
610

    
611
    if(MPV_frame_start(s, avctx) < 0)
612
        return -1;
613

    
614
    ff_er_frame_start(s);
615

    
616
    /* decode each macroblock */
617
    s->mb_x=0;
618
    s->mb_y=0;
619

    
620
    while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
621
        if(ff_h261_resync(h)<0)
622
            break;
623
        h261_decode_gob(h);
624
    }
625
    MPV_frame_end(s);
626

    
627
assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
628
assert(s->current_picture.pict_type == s->pict_type);
629
    *pict= *(AVFrame*)s->current_picture_ptr;
630
    ff_print_debug_info(s, pict);
631

    
632
    *data_size = sizeof(AVFrame);
633

    
634
    return get_consumed_bytes(s, buf_size);
635
}
636

    
637
static av_cold int h261_decode_end(AVCodecContext *avctx)
638
{
639
    H261Context *h= avctx->priv_data;
640
    MpegEncContext *s = &h->s;
641

    
642
    MPV_common_end(s);
643
    return 0;
644
}
645

    
646
AVCodec ff_h261_decoder = {
647
    "h261",
648
    AVMEDIA_TYPE_VIDEO,
649
    CODEC_ID_H261,
650
    sizeof(H261Context),
651
    h261_decode_init,
652
    NULL,
653
    h261_decode_end,
654
    h261_decode_frame,
655
    CODEC_CAP_DR1,
656
    .max_lowres = 3,
657
    .long_name = NULL_IF_CONFIG_SMALL("H.261"),
658
};