summaryrefslogtreecommitdiffstats
path: root/libavcodec/h261dec.c
blob: 7f2fff8684eb7359b32adb58c080e6331731f365 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
/*
 * H.261 decoder
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
 * Copyright (c) 2004 Maarten Daniels
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * H.261 decoder.
 */

#include "libavutil/avassert.h"
#include "avcodec.h"
#include "mpeg_er.h"
#include "mpegutils.h"
#include "mpegvideo.h"
#include "h263.h"
#include "h261.h"
#include "internal.h"

#define H261_MBA_VLC_BITS 9
#define H261_MTYPE_VLC_BITS 6
#define H261_MV_VLC_BITS 7
#define H261_CBP_VLC_BITS 9
#define TCOEFF_VLC_BITS 9
#define MBA_STUFFING 33
#define MBA_STARTCODE 34

static VLC h261_mba_vlc;
static VLC h261_mtype_vlc;
static VLC h261_mv_vlc;
static VLC h261_cbp_vlc;

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

    if (!done) {
        done = 1;
        INIT_VLC_STATIC(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
                        ff_h261_mba_bits, 1, 1,
                        ff_h261_mba_code, 1, 1, 662);
        INIT_VLC_STATIC(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
                        ff_h261_mtype_bits, 1, 1,
                        ff_h261_mtype_code, 1, 1, 80);
        INIT_VLC_STATIC(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
                        &ff_h261_mv_tab[0][1], 2, 1,
                        &ff_h261_mv_tab[0][0], 2, 1, 144);
        INIT_VLC_STATIC(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
                        &ff_h261_cbp_tab[0][1], 2, 1,
                        &ff_h261_cbp_tab[0][0], 2, 1, 512);
        INIT_VLC_RL(ff_h261_rl_tcoeff, 552);
    }
}

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

    // set defaults
    ff_mpv_decode_defaults(s);
    ff_mpv_decode_init(s, avctx);

    s->out_format  = FMT_H261;
    s->low_delay   = 1;
    avctx->pix_fmt = AV_PIX_FMT_YUV420P;

    ff_h261_common_init();
    h261_decode_init_vlc(h);

    h->gob_start_code_skipped = 0;

    return 0;
}

/**
 * Decode the group of blocks header or slice header.
 * @return <0 if an error occurred
 */
static int h261_decode_gob_header(H261Context *h)
{
    unsigned int val;
    MpegEncContext *const s = &h->s;

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

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

    h->gob_start_code_skipped = 0;

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

    /* Check if gob_number is valid */
    if (s->mb_height == 18) { // CIF
        if ((h->gob_number <= 0) || (h->gob_number > 12))
            return -1;
    } else { // QCIF
        if ((h->gob_number != 1) && (h->gob_number != 3) &&
            (h->gob_number != 5))
            return -1;
    }

    /* GEI */
    if (skip_1stop_8data_bits(&s->gb) < 0)
        return AVERROR_INVALIDDATA;

    if (s->qscale == 0) {
        av_log(s->avctx, AV_LOG_ERROR, "qscale has forbidden 0 value\n");
        if (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_COMPLIANT))
            return -1;
    }

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

    return 0;
}

/**
 * Decode the group of blocks / video packet header.
 * @return <0 if no resync found
 */
static int h261_resync(H261Context *h)
{
    MpegEncContext *const s = &h->s;
    int left, ret;

    if (h->gob_start_code_skipped) {
        ret = h261_decode_gob_header(h);
        if (ret >= 0)
            return 0;
    } else {
        if (show_bits(&s->gb, 15) == 0) {
            ret = h261_decode_gob_header(h);
            if (ret >= 0)
                return 0;
        }
        // OK, it is not where it is supposed to be ...
        s->gb = s->last_resync_gb;
        align_get_bits(&s->gb);
        left = get_bits_left(&s->gb);

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

                ret = h261_decode_gob_header(h);
                if (ret >= 0)
                    return 0;

                s->gb = bak;
            }
            skip_bits(&s->gb, 8);
        }
    }

    return -1;
}

/**
 * Decode skipped macroblocks.
 * @return 0
 */
static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2)
{
    MpegEncContext *const s = &h->s;
    int i;

    s->mb_intra = 0;

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

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

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

        s->mv_dir                      = MV_DIR_FORWARD;
        s->mv_type                     = MV_TYPE_16X16;
        s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
        s->mv[0][0][0]                 = 0;
        s->mv[0][0][1]                 = 0;
        s->mb_skipped                  = 1;
        h->mtype                      &= ~MB_TYPE_H261_FIL;

        if (s->current_picture.motion_val[0]) {
            int b_stride = 2*s->mb_width + 1;
            int b_xy     = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
            s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
            s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
        }

        ff_mpv_decode_mb(s, s->block);
    }

    return 0;
}

static const int mvmap[17] = {
    0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16
};

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

    /* check if mv_diff is valid */
    if (mv_diff < 0)
        return v;

    mv_diff = mvmap[mv_diff];

    if (mv_diff && !get_bits1(gb))
        mv_diff = -mv_diff;

    v += mv_diff;
    if (v <= -16)
        v += 32;
    else if (v >= 16)
        v -= 32;

    return v;
}

/**
 * Decode a macroblock.
 * @return <0 if an error occurred
 */
static int h261_decode_block(H261Context *h, int16_t *block, int n, int coded)
{
    MpegEncContext *const s = &h->s;
    int level, i, j, run;
    RLTable *rl = &ff_h261_rl_tcoeff;
    const uint8_t *scan_table;

    /* For the variable length encoding there are two code tables, one being
     * used for the first transmitted LEVEL in INTER, INTER + MC and
     * INTER + MC + FIL blocks, the second for all other LEVELs except the
     * first one in INTRA blocks which is fixed length coded with 8 bits.
     * NOTE: The two code tables only differ in one VLC so we handle that
     * manually. */
    scan_table = s->intra_scantable.permutated;
    if (s->mb_intra) {
        /* DC coef */
        level = get_bits(&s->gb, 8);
        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
        if ((level & 0x7F) == 0) {
            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n",
                   level, s->mb_x, s->mb_y);
            return -1;
        }
        /* The code 1000 0000 is not used, the reconstruction level of 1024
         * being coded as 1111 1111. */
        if (level == 255)
            level = 128;
        block[0] = level;
        i        = 1;
    } else if (coded) {
        // Run  Level   Code
        // EOB          Not possible for first level when cbp is available (that's why the table is different)
        // 0    1       1s
        // *    *       0*
        int check = show_bits(&s->gb, 2);
        i = 0;
        if (check & 0x2) {
            skip_bits(&s->gb, 2);
            block[0] = (check & 0x1) ? -1 : 1;
            i        = 1;
        }
    } else {
        i = 0;
    }
    if (!coded) {
        s->block_last_index[n] = i - 1;
        return 0;
    }
    {
    OPEN_READER(re, &s->gb);
    i--; // offset by -1 to allow direct indexing of scan_table
    for (;;) {
        UPDATE_CACHE(re, &s->gb);
        GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TCOEFF_VLC_BITS, 2, 0);
        if (run == 66) {
            if (level) {
                CLOSE_READER(re, &s->gb);
                av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n",
                       s->mb_x, s->mb_y);
                return -1;
            }
            /* escape */
            /* 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. */
            run   = SHOW_UBITS(re, &s->gb, 6) + 1;
            SKIP_CACHE(re, &s->gb, 6);
            level = SHOW_SBITS(re, &s->gb, 8);
            SKIP_COUNTER(re, &s->gb, 6 + 8);
        } else if (level == 0) {
            break;
        } else {
            if (SHOW_UBITS(re, &s->gb, 1))
                level = -level;
            SKIP_COUNTER(re, &s->gb, 1);
        }
        i += run;
        if (i >= 64) {
            CLOSE_READER(re, &s->gb);
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n",
                   s->mb_x, s->mb_y);
            return -1;
        }
        j        = scan_table[i];
        block[j] = level;
    }
    CLOSE_READER(re, &s->gb);
    }
    s->block_last_index[n] = i;
    return 0;
}

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

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

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

    if (h->mba_diff < 0) {
        if (get_bits_left(&s->gb) <= 7)
            return SLICE_END;

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

    h->mba_diff    += 1;
    h->current_mba += h->mba_diff;

    if (h->current_mba > MBA_STUFFING)
        return SLICE_ERROR;

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

    // Read mtype
    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
    if (h->mtype < 0) {
        av_log(s->avctx, AV_LOG_ERROR, "Invalid mtype index %d\n",
               h->mtype);
        return SLICE_ERROR;
    }
    av_assert0(h->mtype < FF_ARRAY_ELEMS(ff_h261_mtype_map));
    h->mtype = ff_h261_mtype_map[h->mtype];

    // Read mquant
    if (IS_QUANT(h->mtype))
        ff_set_qscale(s, get_bits(&s->gb, 5));

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

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

        h->current_mv_x = decode_mv_component(&s->gb, h->current_mv_x);
        h->current_mv_y = decode_mv_component(&s->gb, h->current_mv_y);
    } else {
        h->current_mv_x = 0;
        h->current_mv_y = 0;
    }

    // Read cbp
    if (HAS_CBP(h->mtype))
        cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;

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

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

    if (s->current_picture.motion_val[0]) {
        int b_stride = 2*s->mb_width + 1;
        int b_xy     = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
        s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
        s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
    }

intra:
    /* decode each block */
    if (s->mb_intra || HAS_CBP(h->mtype)) {
        s->bdsp.clear_blocks(s->block[0]);
        for (i = 0; i < 6; i++) {
            if (h261_decode_block(h, s->block[i], i, cbp & 32) < 0)
                return SLICE_ERROR;
            cbp += cbp;
        }
    } else {
        for (i = 0; i < 6; i++)
            s->block_last_index[i] = -1;
    }

    ff_mpv_decode_mb(s, s->block);

    return SLICE_OK;
}

/**
 * Decode the H.261 picture header.
 * @return <0 if no startcode found
 */
static int h261_decode_picture_header(H261Context *h)
{
    MpegEncContext *const s = &h->s;
    int format, i;
    uint32_t startcode = 0;

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

        if (startcode == 0x10)
            break;
    }

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

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

    s->avctx->framerate = (AVRational) { 30000, 1001 };

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

    format = get_bits1(&s->gb);

    // only 2 formats possible
    if (format == 0) { // QCIF
        s->width     = 176;
        s->height    = 144;
        s->mb_width  = 11;
        s->mb_height = 9;
    } else { // CIF
        s->width     = 352;
        s->height    = 288;
        s->mb_width  = 22;
        s->mb_height = 18;
    }

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

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

    /* PEI */
    if (skip_1stop_8data_bits(&s->gb) < 0)
        return AVERROR_INVALIDDATA;

    /* H.261 has no I-frames, but if we pass AV_PICTURE_TYPE_I for the first
     * frame, the codec crashes if it does not contain all I-blocks
     * (e.g. when a packet is lost). */
    s->pict_type = AV_PICTURE_TYPE_P;

    h->gob_number = 0;
    return 0;
}

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

    ff_set_qscale(s, s->qscale);

    /* decode mb's */
    while (h->current_mba <= MBA_STUFFING) {
        int ret;
        /* DCT & quantize */
        ret = h261_decode_mb(h);
        if (ret < 0) {
            if (ret == SLICE_END) {
                h261_decode_mb_skipped(h, h->current_mba, 33);
                return 0;
            }
            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n",
                   s->mb_x + s->mb_y * s->mb_stride);
            return -1;
        }

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

    return -1;
}

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

    return pos;
}

static int h261_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_frame, AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size       = avpkt->size;
    H261Context *h     = avctx->priv_data;
    MpegEncContext *s  = &h->s;
    int ret;
    AVFrame *pict = data;

    ff_dlog(avctx, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
    ff_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);

    h->gob_start_code_skipped = 0;

retry:
    init_get_bits(&s->gb, buf, buf_size * 8);

    if (!s->context_initialized)
        // we need the IDCT permutation for reading a custom matrix
        ff_mpv_idct_init(s);

    ret = h261_decode_picture_header(h);

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

    if (s->width != avctx->coded_width || s->height != avctx->coded_height) {
        ParseContext pc = s->parse_context; // FIXME move this demuxing hack to libavformat
        s->parse_context.buffer = 0;
        ff_mpv_common_end(s);
        s->parse_context = pc;
    }

    if (!s->context_initialized) {
        if ((ret = ff_mpv_common_init(s)) < 0)
            return ret;

        ret = ff_set_dimensions(avctx, s->width, s->height);
        if (ret < 0)
            return ret;

        goto retry;
    }

    // for skipping the frame
    s->current_picture.f->pict_type = s->pict_type;
    s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;

    if ((avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type == AV_PICTURE_TYPE_B) ||
        (avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type != AV_PICTURE_TYPE_I) ||
         avctx->skip_frame >= AVDISCARD_ALL)
        return get_consumed_bytes(s, buf_size);

    if (ff_mpv_frame_start(s, avctx) < 0)
        return -1;

    ff_mpeg_er_frame_start(s);

    /* decode each macroblock */
    s->mb_x = 0;
    s->mb_y = 0;

    while (h->gob_number < (s->mb_height == 18 ? 12 : 5)) {
        if (h261_resync(h) < 0)
            break;
        h261_decode_gob(h);
    }
    ff_mpv_frame_end(s);

    av_assert0(s->current_picture.f->pict_type == s->current_picture_ptr->f->pict_type);
    av_assert0(s->current_picture.f->pict_type == s->pict_type);

    if ((ret = av_frame_ref(pict, s->current_picture_ptr->f)) < 0)
        return ret;
    ff_print_debug_info(s, s->current_picture_ptr, pict);

    *got_frame = 1;

    return get_consumed_bytes(s, buf_size);
}

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

    ff_mpv_common_end(s);
    return 0;
}

AVCodec ff_h261_decoder = {
    .name           = "h261",
    .long_name      = NULL_IF_CONFIG_SMALL("H.261"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_H261,
    .priv_data_size = sizeof(H261Context),
    .init           = h261_decode_init,
    .close          = h261_decode_end,
    .decode         = h261_decode_frame,
    .capabilities   = AV_CODEC_CAP_DR1,
    .max_lowres     = 3,
};
OpenPOWER on IntegriCloud