summaryrefslogtreecommitdiff
path: root/libavcodec/cavsdec.c
blob: a978fe1a1a92f916b75ba8047a40e6f0e5c6a4c8 (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
691
692
693
694
695
696
697
698
699
700
701
702
703
/*
 * Chinese AVS video (AVS1-P2, JiZhun profile) decoder.
 * Copyright (c) 2006  Stefan Gehrer <stefan.gehrer@gmx.de>
 *
 * 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 cavs.c
 * Chinese AVS video (AVS1-P2, JiZhun profile) decoder
 * @author Stefan Gehrer <stefan.gehrer@gmx.de>
 */

#include "avcodec.h"
#include "bitstream.h"
#include "golomb.h"
#include "cavs.h"

static const uint8_t mv_scan[4] = {
    MV_FWD_X0,MV_FWD_X1,
    MV_FWD_X2,MV_FWD_X3
};

static const uint8_t cbp_tab[64][2] = {
  {63, 0},{15,15},{31,63},{47,31},{ 0,16},{14,32},{13,47},{11,13},
  { 7,14},{ 5,11},{10,12},{ 8, 5},{12,10},{61, 7},{ 4,48},{55, 3},
  { 1, 2},{ 2, 8},{59, 4},{ 3, 1},{62,61},{ 9,55},{ 6,59},{29,62},
  {45,29},{51,27},{23,23},{39,19},{27,30},{46,28},{53, 9},{30, 6},
  {43,60},{37,21},{60,44},{16,26},{21,51},{28,35},{19,18},{35,20},
  {42,24},{26,53},{44,17},{32,37},{58,39},{24,45},{20,58},{17,43},
  {18,42},{48,46},{22,36},{33,33},{25,34},{49,40},{40,52},{36,49},
  {34,50},{50,56},{52,25},{54,22},{41,54},{56,57},{38,41},{57,38}
};

/*****************************************************************************
 *
 * motion vector prediction
 *
 ****************************************************************************/

static inline void store_mvs(AVSContext *h) {
    h->col_mv[(h->mby*h->mb_width + h->mbx)*4 + 0] = h->mv[MV_FWD_X0];
    h->col_mv[(h->mby*h->mb_width + h->mbx)*4 + 1] = h->mv[MV_FWD_X1];
    h->col_mv[(h->mby*h->mb_width + h->mbx)*4 + 2] = h->mv[MV_FWD_X2];
    h->col_mv[(h->mby*h->mb_width + h->mbx)*4 + 3] = h->mv[MV_FWD_X3];
}

static inline void mv_pred_direct(AVSContext *h, vector_t *pmv_fw,
                                  vector_t *col_mv) {
    vector_t *pmv_bw = pmv_fw + MV_BWD_OFFS;
    int den = h->direct_den[col_mv->ref];
    int m = col_mv->x >> 31;

    pmv_fw->dist = h->dist[1];
    pmv_bw->dist = h->dist[0];
    pmv_fw->ref = 1;
    pmv_bw->ref = 0;
    /* scale the co-located motion vector according to its temporal span */
    pmv_fw->x = (((den+(den*col_mv->x*pmv_fw->dist^m)-m-1)>>14)^m)-m;
    pmv_bw->x = m-(((den+(den*col_mv->x*pmv_bw->dist^m)-m-1)>>14)^m);
    m = col_mv->y >> 31;
    pmv_fw->y = (((den+(den*col_mv->y*pmv_fw->dist^m)-m-1)>>14)^m)-m;
    pmv_bw->y = m-(((den+(den*col_mv->y*pmv_bw->dist^m)-m-1)>>14)^m);
}

static inline void mv_pred_sym(AVSContext *h, vector_t *src, enum block_t size) {
    vector_t *dst = src + MV_BWD_OFFS;

    /* backward mv is the scaled and negated forward mv */
    dst->x = -((src->x * h->sym_factor + 256) >> 9);
    dst->y = -((src->y * h->sym_factor + 256) >> 9);
    dst->ref = 0;
    dst->dist = h->dist[0];
    set_mvs(dst, size);
}

/*****************************************************************************
 *
 * residual data decoding
 *
 ****************************************************************************/

/** kth-order exponential golomb code */
static inline int get_ue_code(GetBitContext *gb, int order) {
    if(order) {
        int ret = get_ue_golomb(gb) << order;
        return ret + get_bits(gb,order);
    }
    return get_ue_golomb(gb);
}

/**
 * decode coefficients from one 8x8 block, dequantize, inverse transform
 *  and add them to sample block
 * @param r pointer to 2D VLC table
 * @param esc_golomb_order escape codes are k-golomb with this order k
 * @param qp quantizer
 * @param dst location of sample block
 * @param stride line stride in frame buffer
 */
static int decode_residual_block(AVSContext *h, GetBitContext *gb,
                                 const dec_2dvlc_t *r, int esc_golomb_order,
                                 int qp, uint8_t *dst, int stride) {
    int i, level_code, esc_code, level, run, mask;
    DCTELEM level_buf[65];
    uint8_t run_buf[65];
    DCTELEM *block = h->block;

    for(i=0;i<65;i++) {
        level_code = get_ue_code(gb,r->golomb_order);
        if(level_code >= ESCAPE_CODE) {
            run = ((level_code - ESCAPE_CODE) >> 1) + 1;
            esc_code = get_ue_code(gb,esc_golomb_order);
            level = esc_code + (run > r->max_run ? 1 : r->level_add[run]);
            while(level > r->inc_limit)
                r++;
            mask = -(level_code & 1);
            level = (level^mask) - mask;
        } else {
            level = r->rltab[level_code][0];
            if(!level) //end of block signal
                break;
            run   = r->rltab[level_code][1];
            r += r->rltab[level_code][2];
        }
        level_buf[i] = level;
        run_buf[i] = run;
    }
    if(dequant(h,level_buf, run_buf, block, ff_cavs_dequant_mul[qp],
               ff_cavs_dequant_shift[qp], i))
        return -1;
    h->s.dsp.cavs_idct8_add(dst,block,stride);
    return 0;
}


static inline void decode_residual_chroma(AVSContext *h) {
    if(h->cbp & (1<<4))
        decode_residual_block(h,&h->s.gb,ff_cavs_chroma_dec,0,
                              ff_cavs_chroma_qp[h->qp],h->cu,h->c_stride);
    if(h->cbp & (1<<5))
        decode_residual_block(h,&h->s.gb,ff_cavs_chroma_dec,0,
                              ff_cavs_chroma_qp[h->qp],h->cv,h->c_stride);
}

static inline int decode_residual_inter(AVSContext *h) {
    int block;

    /* get coded block pattern */
    int cbp= get_ue_golomb(&h->s.gb);
    if(cbp > 63){
        av_log(h->s.avctx, AV_LOG_ERROR, "illegal inter cbp\n");
        return -1;
    }
    h->cbp = cbp_tab[cbp][1];

    /* get quantizer */
    if(h->cbp && !h->qp_fixed)
        h->qp = (h->qp + get_se_golomb(&h->s.gb)) & 63;
    for(block=0;block<4;block++)
        if(h->cbp & (1<<block))
            decode_residual_block(h,&h->s.gb,ff_cavs_inter_dec,0,h->qp,
                                  h->cy + h->luma_scan[block], h->l_stride);
    decode_residual_chroma(h);

    return 0;
}

/*****************************************************************************
 *
 * macroblock level
 *
 ****************************************************************************/

static int decode_mb_i(AVSContext *h, int cbp_code) {
    GetBitContext *gb = &h->s.gb;
    int block, pred_mode_uv;
    uint8_t top[18];
    uint8_t *left = NULL;
    uint8_t *d;

    ff_cavs_init_mb(h);

    /* get intra prediction modes from stream */
    for(block=0;block<4;block++) {
        int nA,nB,predpred;
        int pos = ff_cavs_scan3x3[block];

        nA = h->pred_mode_Y[pos-1];
        nB = h->pred_mode_Y[pos-3];
        predpred = FFMIN(nA,nB);
        if(predpred == NOT_AVAIL) // if either is not available
            predpred = INTRA_L_LP;
        if(!get_bits1(gb)){
            int rem_mode= get_bits(gb, 2);
            predpred = rem_mode + (rem_mode >= predpred);
        }
        h->pred_mode_Y[pos] = predpred;
    }
    pred_mode_uv = get_ue_golomb(gb);
    if(pred_mode_uv > 6) {
        av_log(h->s.avctx, AV_LOG_ERROR, "illegal intra chroma pred mode\n");
        return -1;
    }
    ff_cavs_modify_mb_i(h, &pred_mode_uv);

    /* get coded block pattern */
    if(h->pic_type == FF_I_TYPE)
        cbp_code = get_ue_golomb(gb);
    if(cbp_code > 63){
        av_log(h->s.avctx, AV_LOG_ERROR, "illegal intra cbp\n");
        return -1;
    }
    h->cbp = cbp_tab[cbp_code][0];
    if(h->cbp && !h->qp_fixed)
        h->qp = (h->qp + get_se_golomb(gb)) & 63; //qp_delta

    /* luma intra prediction interleaved with residual decode/transform/add */
    for(block=0;block<4;block++) {
        d = h->cy + h->luma_scan[block];
        ff_cavs_load_intra_pred_luma(h, top, &left, block);
        h->intra_pred_l[h->pred_mode_Y[ff_cavs_scan3x3[block]]]
            (d, top, left, h->l_stride);
        if(h->cbp & (1<<block))
            decode_residual_block(h,gb,ff_cavs_intra_dec,1,h->qp,d,h->l_stride);
    }

    /* chroma intra prediction */
    ff_cavs_load_intra_pred_chroma(h);
    h->intra_pred_c[pred_mode_uv](h->cu, &h->top_border_u[h->mbx*10],
                                  h->left_border_u, h->c_stride);
    h->intra_pred_c[pred_mode_uv](h->cv, &h->top_border_v[h->mbx*10],
                                  h->left_border_v, h->c_stride);

    decode_residual_chroma(h);
    ff_cavs_filter(h,I_8X8);
    set_mv_intra(h);
    return 0;
}

static void decode_mb_p(AVSContext *h, enum mb_t mb_type) {
    GetBitContext *gb = &h->s.gb;
    int ref[4];

    ff_cavs_init_mb(h);
    switch(mb_type) {
    case P_SKIP:
        ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_PSKIP,  BLK_16X16, 0);
        break;
    case P_16X16:
        ref[0] = h->ref_flag ? 0 : get_bits1(gb);
        ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16,ref[0]);
        break;
    case P_16X8:
        ref[0] = h->ref_flag ? 0 : get_bits1(gb);
        ref[2] = h->ref_flag ? 0 : get_bits1(gb);
        ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_TOP,    BLK_16X8, ref[0]);
        ff_cavs_mv(h, MV_FWD_X2, MV_FWD_A1, MV_PRED_LEFT,   BLK_16X8, ref[2]);
        break;
    case P_8X16:
        ref[0] = h->ref_flag ? 0 : get_bits1(gb);
        ref[1] = h->ref_flag ? 0 : get_bits1(gb);
        ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_LEFT,   BLK_8X16, ref[0]);
        ff_cavs_mv(h, MV_FWD_X1, MV_FWD_C2, MV_PRED_TOPRIGHT,BLK_8X16, ref[1]);
        break;
    case P_8X8:
        ref[0] = h->ref_flag ? 0 : get_bits1(gb);
        ref[1] = h->ref_flag ? 0 : get_bits1(gb);
        ref[2] = h->ref_flag ? 0 : get_bits1(gb);
        ref[3] = h->ref_flag ? 0 : get_bits1(gb);
        ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_MEDIAN,   BLK_8X8, ref[0]);
        ff_cavs_mv(h, MV_FWD_X1, MV_FWD_C2, MV_PRED_MEDIAN,   BLK_8X8, ref[1]);
        ff_cavs_mv(h, MV_FWD_X2, MV_FWD_X1, MV_PRED_MEDIAN,   BLK_8X8, ref[2]);
        ff_cavs_mv(h, MV_FWD_X3, MV_FWD_X0, MV_PRED_MEDIAN,   BLK_8X8, ref[3]);
    }
    ff_cavs_inter(h, mb_type);
    set_intra_mode_default(h);
    store_mvs(h);
    if(mb_type != P_SKIP)
        decode_residual_inter(h);
    ff_cavs_filter(h,mb_type);
    *h->col_type = mb_type;
}

static void decode_mb_b(AVSContext *h, enum mb_t mb_type) {
    int block;
    enum sub_mb_t sub_type[4];
    int flags;

    ff_cavs_init_mb(h);

    /* reset all MVs */
    h->mv[MV_FWD_X0] = ff_cavs_dir_mv;
    set_mvs(&h->mv[MV_FWD_X0], BLK_16X16);
    h->mv[MV_BWD_X0] = ff_cavs_dir_mv;
    set_mvs(&h->mv[MV_BWD_X0], BLK_16X16);
    switch(mb_type) {
    case B_SKIP:
    case B_DIRECT:
        if(!(*h->col_type)) {
            /* intra MB at co-location, do in-plane prediction */
            ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_BSKIP, BLK_16X16, 1);
            ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_BSKIP, BLK_16X16, 0);
        } else
            /* direct prediction from co-located P MB, block-wise */
            for(block=0;block<4;block++)
                mv_pred_direct(h,&h->mv[mv_scan[block]],
                            &h->col_mv[(h->mby*h->mb_width+h->mbx)*4 + block]);
        break;
    case B_FWD_16X16:
        ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16, 1);
        break;
    case B_SYM_16X16:
        ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_MEDIAN, BLK_16X16, 1);
        mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_16X16);
        break;
    case B_BWD_16X16:
        ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_MEDIAN, BLK_16X16, 0);
        break;
    case B_8X8:
        for(block=0;block<4;block++)
            sub_type[block] = get_bits(&h->s.gb,2);
        for(block=0;block<4;block++) {
            switch(sub_type[block]) {
            case B_SUB_DIRECT:
                if(!(*h->col_type)) {
                    /* intra MB at co-location, do in-plane prediction */
                    ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,
                            MV_PRED_BSKIP, BLK_8X8, 1);
                    ff_cavs_mv(h, mv_scan[block]+MV_BWD_OFFS,
                            mv_scan[block]-3+MV_BWD_OFFS,
                            MV_PRED_BSKIP, BLK_8X8, 0);
                } else
                    mv_pred_direct(h,&h->mv[mv_scan[block]],
                                   &h->col_mv[(h->mby*h->mb_width + h->mbx)*4 + block]);
                break;
            case B_SUB_FWD:
                ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,
                        MV_PRED_MEDIAN, BLK_8X8, 1);
                break;
            case B_SUB_SYM:
                ff_cavs_mv(h, mv_scan[block], mv_scan[block]-3,
                        MV_PRED_MEDIAN, BLK_8X8, 1);
                mv_pred_sym(h, &h->mv[mv_scan[block]], BLK_8X8);
                break;
            }
        }
        for(block=0;block<4;block++) {
            if(sub_type[block] == B_SUB_BWD)
                ff_cavs_mv(h, mv_scan[block]+MV_BWD_OFFS,
                        mv_scan[block]+MV_BWD_OFFS-3,
                        MV_PRED_MEDIAN, BLK_8X8, 0);
        }
        break;
    default:
        assert((mb_type > B_SYM_16X16) && (mb_type < B_8X8));
        flags = ff_cavs_partition_flags[mb_type];
        if(mb_type & 1) { /* 16x8 macroblock types */
            if(flags & FWD0)
                ff_cavs_mv(h, MV_FWD_X0, MV_FWD_C2, MV_PRED_TOP,  BLK_16X8, 1);
            if(flags & SYM0)
                mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_16X8);
            if(flags & FWD1)
                ff_cavs_mv(h, MV_FWD_X2, MV_FWD_A1, MV_PRED_LEFT, BLK_16X8, 1);
            if(flags & SYM1)
                mv_pred_sym(h, &h->mv[MV_FWD_X2], BLK_16X8);
            if(flags & BWD0)
                ff_cavs_mv(h, MV_BWD_X0, MV_BWD_C2, MV_PRED_TOP,  BLK_16X8, 0);
            if(flags & BWD1)
                ff_cavs_mv(h, MV_BWD_X2, MV_BWD_A1, MV_PRED_LEFT, BLK_16X8, 0);
        } else {          /* 8x16 macroblock types */
            if(flags & FWD0)
                ff_cavs_mv(h, MV_FWD_X0, MV_FWD_B3, MV_PRED_LEFT, BLK_8X16, 1);
            if(flags & SYM0)
                mv_pred_sym(h, &h->mv[MV_FWD_X0], BLK_8X16);
            if(flags & FWD1)
                ff_cavs_mv(h,MV_FWD_X1,MV_FWD_C2,MV_PRED_TOPRIGHT,BLK_8X16,1);
            if(flags & SYM1)
                mv_pred_sym(h, &h->mv[MV_FWD_X1], BLK_8X16);
            if(flags & BWD0)
                ff_cavs_mv(h, MV_BWD_X0, MV_BWD_B3, MV_PRED_LEFT, BLK_8X16, 0);
            if(flags & BWD1)
                ff_cavs_mv(h,MV_BWD_X1,MV_BWD_C2,MV_PRED_TOPRIGHT,BLK_8X16,0);
        }
    }
    ff_cavs_inter(h, mb_type);
    set_intra_mode_default(h);
    if(mb_type != B_SKIP)
        decode_residual_inter(h);
    ff_cavs_filter(h,mb_type);
}

/*****************************************************************************
 *
 * slice level
 *
 ****************************************************************************/

static inline int decode_slice_header(AVSContext *h, GetBitContext *gb) {
    if(h->stc > 0xAF)
        av_log(h->s.avctx, AV_LOG_ERROR, "unexpected start code 0x%02x\n", h->stc);
    h->mby = h->stc;
    if((h->mby == 0) && (!h->qp_fixed)){
        h->qp_fixed = get_bits1(gb);
        h->qp = get_bits(gb,6);
    }
    /* inter frame or second slice can have weighting params */
    if((h->pic_type != FF_I_TYPE) || (!h->pic_structure && h->mby >= h->mb_width/2))
        if(get_bits1(gb)) { //slice_weighting_flag
            av_log(h->s.avctx, AV_LOG_ERROR,
                   "weighted prediction not yet supported\n");
        }
    return 0;
}

static inline void check_for_slice(AVSContext *h) {
    GetBitContext *gb = &h->s.gb;
    int align;
    align = (-get_bits_count(gb)) & 7;
    if((show_bits_long(gb,24+align) & 0xFFFFFF) == 0x000001) {
        skip_bits_long(gb,24+align);
        h->stc = get_bits(gb,8);
        decode_slice_header(h,gb);
    }
}

/*****************************************************************************
 *
 * frame level
 *
 ****************************************************************************/

static int decode_pic(AVSContext *h) {
    MpegEncContext *s = &h->s;
    int skip_count;
    enum mb_t mb_type;

    if (!s->context_initialized) {
        s->avctx->idct_algo = FF_IDCT_CAVS;
        if (MPV_common_init(s) < 0)
            return -1;
        ff_init_scantable(s->dsp.idct_permutation,&h->scantable,ff_zigzag_direct);
    }
    skip_bits(&s->gb,16);//bbv_dwlay
    if(h->stc == PIC_PB_START_CODE) {
        h->pic_type = get_bits(&s->gb,2) + FF_I_TYPE;
        if(h->pic_type > FF_B_TYPE) {
            av_log(s->avctx, AV_LOG_ERROR, "illegal picture type\n");
            return -1;
        }
        /* make sure we have the reference frames we need */
        if(!h->DPB[0].data[0] ||
          (!h->DPB[1].data[0] && h->pic_type == FF_B_TYPE))
            return -1;
    } else {
        h->pic_type = FF_I_TYPE;
        if(get_bits1(&s->gb))
            skip_bits(&s->gb,16);//time_code
    }
    /* release last B frame */
    if(h->picture.data[0])
        s->avctx->release_buffer(s->avctx, (AVFrame *)&h->picture);

    s->avctx->get_buffer(s->avctx, (AVFrame *)&h->picture);
    ff_cavs_init_pic(h);
    h->picture.poc = get_bits(&s->gb,8)*2;

    /* get temporal distances and MV scaling factors */
    if(h->pic_type != FF_B_TYPE) {
        h->dist[0] = (h->picture.poc - h->DPB[0].poc  + 512) % 512;
    } else {
        h->dist[0] = (h->DPB[0].poc  - h->picture.poc + 512) % 512;
    }
    h->dist[1] = (h->picture.poc - h->DPB[1].poc  + 512) % 512;
    h->scale_den[0] = h->dist[0] ? 512/h->dist[0] : 0;
    h->scale_den[1] = h->dist[1] ? 512/h->dist[1] : 0;
    if(h->pic_type == FF_B_TYPE) {
        h->sym_factor = h->dist[0]*h->scale_den[1];
    } else {
        h->direct_den[0] = h->dist[0] ? 16384/h->dist[0] : 0;
        h->direct_den[1] = h->dist[1] ? 16384/h->dist[1] : 0;
    }

    if(s->low_delay)
        get_ue_golomb(&s->gb); //bbv_check_times
    h->progressive             = get_bits1(&s->gb);
    if(h->progressive)
        h->pic_structure = 1;
    else if(!(h->pic_structure = get_bits1(&s->gb) && (h->stc == PIC_PB_START_CODE)) )
        skip_bits1(&s->gb);     //advanced_pred_mode_disable
    skip_bits1(&s->gb);        //top_field_first
    skip_bits1(&s->gb);        //repeat_first_field
    h->qp_fixed                = get_bits1(&s->gb);
    h->qp                      = get_bits(&s->gb,6);
    if(h->pic_type == FF_I_TYPE) {
        if(!h->progressive && !h->pic_structure)
            skip_bits1(&s->gb);//what is this?
        skip_bits(&s->gb,4);   //reserved bits
    } else {
        if(!(h->pic_type == FF_B_TYPE && h->pic_structure == 1))
            h->ref_flag        = get_bits1(&s->gb);
        skip_bits(&s->gb,4);   //reserved bits
        h->skip_mode_flag      = get_bits1(&s->gb);
    }
    h->loop_filter_disable     = get_bits1(&s->gb);
    if(!h->loop_filter_disable && get_bits1(&s->gb)) {
        h->alpha_offset        = get_se_golomb(&s->gb);
        h->beta_offset         = get_se_golomb(&s->gb);
    } else {
        h->alpha_offset = h->beta_offset  = 0;
    }
    check_for_slice(h);
    if(h->pic_type == FF_I_TYPE) {
        do {
            decode_mb_i(h, 0);
        } while(ff_cavs_next_mb(h));
    } else if(h->pic_type == FF_P_TYPE) {
        do {
            if(h->skip_mode_flag) {
                skip_count = get_ue_golomb(&s->gb);
                while(skip_count--) {
                    decode_mb_p(h,P_SKIP);
                    if(!ff_cavs_next_mb(h))
                        goto done;
                }
                mb_type = get_ue_golomb(&s->gb) + P_16X16;
            } else
                mb_type = get_ue_golomb(&s->gb) + P_SKIP;
            if(mb_type > P_8X8) {
                decode_mb_i(h, mb_type - P_8X8 - 1);
            } else
                decode_mb_p(h,mb_type);
        } while(ff_cavs_next_mb(h));
    } else { /* FF_B_TYPE */
        do {
            if(h->skip_mode_flag) {
                skip_count = get_ue_golomb(&s->gb);
                while(skip_count--) {
                    decode_mb_b(h,B_SKIP);
                    if(!ff_cavs_next_mb(h))
                        goto done;
                }
                mb_type = get_ue_golomb(&s->gb) + B_DIRECT;
            } else
                mb_type = get_ue_golomb(&s->gb) + B_SKIP;
            if(mb_type > B_8X8) {
                decode_mb_i(h, mb_type - B_8X8 - 1);
            } else
                decode_mb_b(h,mb_type);
        } while(ff_cavs_next_mb(h));
    }
 done:
    if(h->pic_type != FF_B_TYPE) {
        if(h->DPB[1].data[0])
            s->avctx->release_buffer(s->avctx, (AVFrame *)&h->DPB[1]);
        memcpy(&h->DPB[1], &h->DPB[0], sizeof(Picture));
        memcpy(&h->DPB[0], &h->picture, sizeof(Picture));
        memset(&h->picture,0,sizeof(Picture));
    }
    return 0;
}

/*****************************************************************************
 *
 * headers and interface
 *
 ****************************************************************************/

static int decode_seq_header(AVSContext *h) {
    MpegEncContext *s = &h->s;
    int frame_rate_code;

    h->profile =         get_bits(&s->gb,8);
    h->level =           get_bits(&s->gb,8);
    skip_bits1(&s->gb); //progressive sequence
    s->width =           get_bits(&s->gb,14);
    s->height =          get_bits(&s->gb,14);
    skip_bits(&s->gb,2); //chroma format
    skip_bits(&s->gb,3); //sample_precision
    h->aspect_ratio =    get_bits(&s->gb,4);
    frame_rate_code =    get_bits(&s->gb,4);
    skip_bits(&s->gb,18);//bit_rate_lower
    skip_bits1(&s->gb);  //marker_bit
    skip_bits(&s->gb,12);//bit_rate_upper
    s->low_delay =       get_bits1(&s->gb);
    h->mb_width  = (s->width  + 15) >> 4;
    h->mb_height = (s->height + 15) >> 4;
    h->s.avctx->time_base.den = ff_frame_rate_tab[frame_rate_code].num;
    h->s.avctx->time_base.num = ff_frame_rate_tab[frame_rate_code].den;
    h->s.avctx->width  = s->width;
    h->s.avctx->height = s->height;
    if(!h->top_qp)
        ff_cavs_init_top_lines(h);
    return 0;
}

static void cavs_flush(AVCodecContext * avctx) {
    AVSContext *h = avctx->priv_data;
    h->got_keyframe = 0;
}

static int cavs_decode_frame(AVCodecContext * avctx,void *data, int *data_size,
                             const uint8_t * buf, int buf_size) {
    AVSContext *h = avctx->priv_data;
    MpegEncContext *s = &h->s;
    int input_size;
    const uint8_t *buf_end;
    const uint8_t *buf_ptr;
    AVFrame *picture = data;
    uint32_t stc = -1;

    s->avctx = avctx;

    if (buf_size == 0) {
        if(!s->low_delay && h->DPB[0].data[0]) {
            *data_size = sizeof(AVPicture);
            *picture = *(AVFrame *) &h->DPB[0];
        }
        return 0;
    }

    buf_ptr = buf;
    buf_end = buf + buf_size;
    for(;;) {
        buf_ptr = ff_find_start_code(buf_ptr,buf_end, &stc);
        if(stc & 0xFFFFFE00)
            return FFMAX(0, buf_ptr - buf - s->parse_context.last_index);
        input_size = (buf_end - buf_ptr)*8;
        switch(stc) {
        case CAVS_START_CODE:
            init_get_bits(&s->gb, buf_ptr, input_size);
            decode_seq_header(h);
            break;
        case PIC_I_START_CODE:
            if(!h->got_keyframe) {
                if(h->DPB[0].data[0])
                    avctx->release_buffer(avctx, (AVFrame *)&h->DPB[0]);
                if(h->DPB[1].data[0])
                    avctx->release_buffer(avctx, (AVFrame *)&h->DPB[1]);
                h->got_keyframe = 1;
            }
        case PIC_PB_START_CODE:
            *data_size = 0;
            if(!h->got_keyframe)
                break;
            init_get_bits(&s->gb, buf_ptr, input_size);
            h->stc = stc;
            if(decode_pic(h))
                break;
            *data_size = sizeof(AVPicture);
            if(h->pic_type != FF_B_TYPE) {
                if(h->DPB[1].data[0]) {
                    *picture = *(AVFrame *) &h->DPB[1];
                } else {
                    *data_size = 0;
                }
            } else
                *picture = *(AVFrame *) &h->picture;
            break;
        case EXT_START_CODE:
            //mpeg_decode_extension(avctx,buf_ptr, input_size);
            break;
        case USER_START_CODE:
            //mpeg_decode_user_data(avctx,buf_ptr, input_size);
            break;
        default:
            if (stc >= SLICE_MIN_START_CODE &&
                stc <= SLICE_MAX_START_CODE) {
                init_get_bits(&s->gb, buf_ptr, input_size);
                decode_slice_header(h, &s->gb);
            }
            break;
        }
    }
}

AVCodec cavs_decoder = {
    "cavs",
    CODEC_TYPE_VIDEO,
    CODEC_ID_CAVS,
    sizeof(AVSContext),
    ff_cavs_init,
    NULL,
    ff_cavs_end,
    cavs_decode_frame,
    CODEC_CAP_DR1 | CODEC_CAP_DELAY,
    .flush= cavs_flush,
    .long_name= NULL_IF_CONFIG_SMALL("Chinese AVS video (AVS1-P2, JiZhun profile)"),
};