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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 library is free software; you can redistribute it and/or
7
 * modify it under the terms of the GNU Lesser General Public
8
 * License as published by the Free Software Foundation; either
9
 * version 2 of the License, or (at your option) any later version.
10
 *
11
 * This library is distributed in the hope that it will be useful,
12
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14
 * Lesser General Public License for more details.
15
 *
16
 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library; if not, write to the Free Software
18
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
19
 */
20

    
21
/**
22
 * @file h261.c
23
 * h261codec.
24
 */
25

    
26
#include "common.h"
27
#include "dsputil.h"
28
#include "avcodec.h"
29
#include "mpegvideo.h"
30
#include "h261data.h"
31

    
32

    
33
#define H261_MBA_VLC_BITS 9
34
#define H261_MTYPE_VLC_BITS 6
35
#define H261_MV_VLC_BITS 7
36
#define H261_CBP_VLC_BITS 9
37
#define TCOEFF_VLC_BITS 9
38

    
39
#define MBA_STUFFING 33
40
#define MBA_STARTCODE 34
41
#define IS_FIL(a)    ((a)&MB_TYPE_H261_FIL)
42

    
43
/**
44
 * H261Context
45
 */
46
typedef struct H261Context{
47
    MpegEncContext s;
48

    
49
    int current_mba;
50
    int mba_diff;
51
    int mtype;
52
    int current_mv_x;
53
    int current_mv_y;
54
    int gob_number;
55
    int bits_left; //8 - nr of bits left of the following frame in the last byte in this frame
56
    int last_bits; //bits left of the following frame in the last byte in this frame
57
    int gob_start_code_skipped; // 1 if gob start code is already read before gob header is read
58
}H261Context;
59

    
60
void ff_h261_loop_filter(H261Context * h){
61
    MpegEncContext * const s = &h->s;
62
    const int linesize  = s->linesize;
63
    const int uvlinesize= s->uvlinesize;
64
    uint8_t *dest_y = s->dest[0];
65
    uint8_t *dest_cb= s->dest[1];
66
    uint8_t *dest_cr= s->dest[2];
67
    
68
    s->dsp.h261_loop_filter(dest_y                   , linesize);
69
    s->dsp.h261_loop_filter(dest_y                + 8, linesize);
70
    s->dsp.h261_loop_filter(dest_y + 8 * linesize    , linesize);
71
    s->dsp.h261_loop_filter(dest_y + 8 * linesize + 8, linesize);
72
    s->dsp.h261_loop_filter(dest_cb, uvlinesize);
73
    s->dsp.h261_loop_filter(dest_cr, uvlinesize);
74
}
75

    
76
static int h261_decode_block(H261Context *h, DCTELEM *block,
77
                             int n, int coded);
78
static int h261_decode_mb(H261Context *h);
79
void ff_set_qscale(MpegEncContext * s, int qscale);
80

    
81
/***********************************************/
82
/* decoding */
83

    
84
static VLC h261_mba_vlc;
85
static VLC h261_mtype_vlc;
86
static VLC h261_mv_vlc;
87
static VLC h261_cbp_vlc;
88

    
89
void init_vlc_rl(RLTable *rl);
90

    
91
static void h261_decode_init_vlc(H261Context *h){
92
    static int done = 0;
93

    
94
    if(!done){
95
        done = 1;
96
        init_vlc(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
97
                 h261_mba_bits, 1, 1,
98
                 h261_mba_code, 1, 1);
99
        init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
100
                 h261_mtype_bits, 1, 1,
101
                 h261_mtype_code, 1, 1);
102
        init_vlc(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
103
                 &h261_mv_tab[0][1], 2, 1,
104
                 &h261_mv_tab[0][0], 2, 1);
105
        init_vlc(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
106
                 &h261_cbp_tab[0][1], 2, 1,
107
                 &h261_cbp_tab[0][0], 2, 1);
108
        init_rl(&h261_rl_tcoeff);
109
        init_vlc_rl(&h261_rl_tcoeff);
110
    }
111
}
112

    
113
static int h261_decode_init(AVCodecContext *avctx){
114
    H261Context *h= avctx->priv_data;
115
    MpegEncContext * const s = &h->s;
116

    
117
    // set defaults
118
    MPV_decode_defaults(s);
119
    s->avctx = avctx;
120

    
121
    s->width  = s->avctx->coded_width;
122
    s->height = s->avctx->coded_height;
123
    s->codec_id = s->avctx->codec->id;
124

    
125
    s->out_format = FMT_H261;
126
    s->low_delay= 1;
127
    avctx->pix_fmt= PIX_FMT_YUV420P;
128

    
129
    s->codec_id= avctx->codec->id;
130

    
131
    h261_decode_init_vlc(h);
132

    
133
    h->gob_start_code_skipped = 0;
134
    
135
    return 0;
136
}
137

    
138
/**
139
 * decodes the group of blocks header or slice header.
140
 * @return <0 if an error occured
141
 */
142
static int h261_decode_gob_header(H261Context *h){
143
    unsigned int val;
144
    MpegEncContext * const s = &h->s;
145
    
146
    if ( !h->gob_start_code_skipped ){
147
        /* Check for GOB Start Code */
148
        val = show_bits(&s->gb, 15);
149
        if(val)
150
            return -1;
151

    
152
        /* We have a GBSC */
153
        skip_bits(&s->gb, 16);
154
    }
155

    
156
    h->gob_start_code_skipped = 0;
157

    
158
    h->gob_number = get_bits(&s->gb, 4); /* GN */
159
    s->qscale = get_bits(&s->gb, 5); /* GQUANT */
160

    
161
    /* Check if gob_number is valid */
162
    if (s->mb_height==18){ //cif
163
        if ((h->gob_number<=0) || (h->gob_number>12))
164
            return -1;
165
    }
166
    else{ //qcif
167
        if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
168
            return -1;
169
    }
170

    
171
    /* GEI */
172
    while (get_bits1(&s->gb) != 0) {
173
        skip_bits(&s->gb, 8);
174
    }
175

    
176
    if(s->qscale==0)
177
        return -1;
178

    
179
    // For the first transmitted macroblock in a GOB, MBA is the absolute address. For
180
    // subsequent macroblocks, MBA is the difference between the absolute addresses of
181
    // the macroblock and the last transmitted macroblock.
182
    h->current_mba = 0;
183
    h->mba_diff = 0;
184

    
185
    return 0;
186
}
187

    
188
/**
189
 * decodes the group of blocks / video packet header.
190
 * @return <0 if no resync found
191
 */
192
static int ff_h261_resync(H261Context *h){
193
    MpegEncContext * const s = &h->s;
194
    int left, ret;
195

    
196
    if ( h->gob_start_code_skipped ){
197
        ret= h261_decode_gob_header(h);
198
        if(ret>=0)
199
            return 0;
200
    }
201
    else{
202
        if(show_bits(&s->gb, 15)==0){
203
            ret= h261_decode_gob_header(h);
204
            if(ret>=0)
205
                return 0;
206
        }
207
        //ok, its not where its supposed to be ...
208
        s->gb= s->last_resync_gb;
209
        align_get_bits(&s->gb);
210
        left= s->gb.size_in_bits - get_bits_count(&s->gb);
211

    
212
        for(;left>15+1+4+5; left-=8){
213
            if(show_bits(&s->gb, 15)==0){
214
                GetBitContext bak= s->gb;
215

    
216
                ret= h261_decode_gob_header(h);
217
                if(ret>=0)
218
                    return 0;
219

    
220
                s->gb= bak;
221
            }
222
            skip_bits(&s->gb, 8);
223
        }
224
    }
225

    
226
    return -1;
227
}
228

    
229
/**
230
 * decodes skipped macroblocks
231
 * @return 0
232
 */
233
static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
234
{
235
    MpegEncContext * const s = &h->s;
236
    int i;
237
    
238
    s->mb_intra = 0;
239

    
240
    for(i=mba1; i<mba2; i++){
241
        int j, xy;
242

    
243
        s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
244
        s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
245
        xy = s->mb_x + s->mb_y * s->mb_stride;
246
        ff_init_block_index(s);
247
        ff_update_block_index(s);
248
        s->dsp.clear_blocks(s->block[0]);
249

    
250
        for(j=0;j<6;j++)
251
            s->block_last_index[j] = -1;
252

    
253
        s->mv_dir = MV_DIR_FORWARD;
254
        s->mv_type = MV_TYPE_16X16;
255
        s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
256
        s->mv[0][0][0] = 0;
257
        s->mv[0][0][1] = 0;
258
        s->mb_skiped = 1;
259

    
260
        MPV_decode_mb(s, s->block);
261
    }
262

    
263
    return 0;
264
}
265

    
266
static int decode_mv_component(GetBitContext *gb, int v){
267
    int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
268

    
269
    /* check if mv_diff is valid */
270
    if ( mv_diff < 0 )
271
        return v;
272

    
273
    mv_diff = mvmap[mv_diff];
274

    
275
    if(mv_diff && !get_bits1(gb))
276
        mv_diff= -mv_diff;
277
    
278
    v += mv_diff;
279
    if     (v <=-16) v+= 32;
280
    else if(v >= 16) v-= 32;
281

    
282
    return v;
283
}
284

    
285
static int h261_decode_mb(H261Context *h){
286
    MpegEncContext * const s = &h->s;
287
    int i, cbp, xy, old_mtype;
288

    
289
    cbp = 63;
290
    // Read mba
291
    do{
292
        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
293

    
294
        /* Check for slice end */
295
        /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
296
        if (h->mba_diff == MBA_STARTCODE){ // start code
297
            h->gob_start_code_skipped = 1;
298
            return SLICE_END;
299
        }
300
    }
301
    while( h->mba_diff == MBA_STUFFING ); // stuffing
302

    
303
    if ( h->mba_diff < 0 ){
304
        if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
305
            return SLICE_END;
306

    
307
        av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
308
        return SLICE_ERROR;
309
    }
310

    
311
    h->mba_diff += 1;
312
    h->current_mba += h->mba_diff;
313

    
314
    if ( h->current_mba > MBA_STUFFING )
315
        return SLICE_ERROR;
316
    
317
    s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
318
    s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
319
    xy = s->mb_x + s->mb_y * s->mb_stride;
320
    ff_init_block_index(s);
321
    ff_update_block_index(s);
322
    s->dsp.clear_blocks(s->block[0]);
323

    
324
    // Read mtype
325
    old_mtype = h->mtype;
326
    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
327
    h->mtype = h261_mtype_map[h->mtype];
328

    
329
    // Read mquant
330
    if ( IS_QUANT ( h->mtype ) ){
331
        ff_set_qscale(s, get_bits(&s->gb, 5));
332
    }
333

    
334
    s->mb_intra = IS_INTRA4x4(h->mtype);
335

    
336
    // Read mv
337
    if ( IS_16X16 ( h->mtype ) ){
338
        // Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the
339
        // vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the
340
        // following three situations:
341
        // 1) evaluating MVD for macroblocks 1, 12 and 23;
342
        // 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
343
        // 3) MTYPE of the previous macroblock was not MC.
344
        if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) ||
345
             ( h->mba_diff != 1) || ( !IS_16X16 ( old_mtype ) ))
346
        {
347
            h->current_mv_x = 0;
348
            h->current_mv_y = 0;
349
        }
350

    
351
        h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
352
        h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
353
    }
354

    
355
    // Read cbp
356
    if ( HAS_CBP( h->mtype ) ){
357
        cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
358
    }
359

    
360
    if(s->mb_intra){
361
        s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
362
        goto intra;
363
    }
364

    
365
    //set motion vectors
366
    s->mv_dir = MV_DIR_FORWARD;
367
    s->mv_type = MV_TYPE_16X16;
368
    s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
369
    if(IS_16X16 ( h->mtype )){
370
        s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation
371
        s->mv[0][0][1] = h->current_mv_y * 2;
372
    }
373
    else{
374
        h->current_mv_x = s->mv[0][0][0] = 0;
375
        h->current_mv_x = s->mv[0][0][1] = 0;
376
    }
377

    
378
intra:
379
    /* decode each block */
380
    if(s->mb_intra || HAS_CBP(h->mtype)){
381
        for (i = 0; i < 6; i++) {
382
            if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
383
                return SLICE_ERROR;
384
            }
385
            cbp+=cbp;
386
        }
387
    }
388

    
389
    MPV_decode_mb(s, s->block);
390

    
391
    if(IS_FIL (h->mtype)){
392
        ff_h261_loop_filter(h);
393
    }
394

    
395
    return SLICE_OK;
396
}
397

    
398
/**
399
 * decodes a macroblock
400
 * @return <0 if an error occured
401
 */
402
static int h261_decode_block(H261Context * h, DCTELEM * block,
403
                             int n, int coded)
404
{
405
    MpegEncContext * const s = &h->s;
406
    int code, level, i, j, run;
407
    RLTable *rl = &h261_rl_tcoeff;
408
    const uint8_t *scan_table;
409
    
410
    // For the variable length encoding there are two code tables, one being used for
411
    // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
412
    // for all other LEVELs except the first one in INTRA blocks which is fixed length
413
    // coded with 8 bits.
414
    // NOTE: the two code tables only differ in one VLC so we handle that manually.
415
    scan_table = s->intra_scantable.permutated;
416
    if (s->mb_intra){
417
        /* DC coef */
418
        level = get_bits(&s->gb, 8);
419
        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
420
        if((level&0x7F) == 0){
421
            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
422
            return -1;
423
        }
424
        // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
425
        if (level == 255)
426
            level = 128;
427
        block[0] = level;
428
        i = 1;
429
    }else if(coded){
430
        // Run  Level   Code
431
        // EOB                  Not possible for first level when cbp is available (that's why the table is different)
432
        // 0    1               1s
433
        // *    *               0*
434
        int check = show_bits(&s->gb, 2);
435
        i = 0;
436
        if ( check & 0x2 ){
437
            skip_bits(&s->gb, 2);
438
            block[0] = ( check & 0x1 ) ? -1 : 1;
439
            i = 1;
440
        }
441
    }else{
442
        i = 0;
443
    }
444
    if(!coded){
445
        s->block_last_index[n] = i - 1;
446
        return 0;
447
    }
448
    for(;;){
449
        code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
450
        if (code < 0){
451
            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
452
            return -1;
453
        }
454
        if (code == rl->n) {
455
            /* escape */
456
            // 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.
457
            run = get_bits(&s->gb, 6);
458
            level = (int8_t)get_bits(&s->gb, 8);
459
        }else if(code == 0){
460
            break;
461
        }else{
462
            run = rl->table_run[code];
463
            level = rl->table_level[code];
464
            if (get_bits1(&s->gb))
465
                level = -level;
466
        }
467
        i += run;
468
        if (i >= 64){
469
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
470
            return -1;
471
        }
472
        j = scan_table[i];
473
        block[j] = level;
474
        i++;
475
    }
476
    s->block_last_index[n] = i-1;
477
    return 0;
478
}
479

    
480
/**
481
 * decodes the H261 picture header.
482
 * @return <0 if no startcode found
483
 */
484
int h261_decode_picture_header(H261Context *h){
485
    MpegEncContext * const s = &h->s;
486
    int format, i;
487
    uint32_t startcode= 0;
488

    
489
    for(i= s->gb.size_in_bits - get_bits_count(&s->gb); i>24; i-=1){
490
        startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
491

    
492
        if(startcode == 0x10)
493
            break;
494
    }
495

    
496
    if (startcode != 0x10){
497
        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
498
        return -1;
499
    }
500

    
501
    /* temporal reference */
502
    s->picture_number = get_bits(&s->gb, 5); /* picture timestamp */
503

    
504
    /* PTYPE starts here */
505
    skip_bits1(&s->gb); /* split screen off */
506
    skip_bits1(&s->gb); /* camera  off */
507
    skip_bits1(&s->gb); /* freeze picture release off */
508

    
509
    format = get_bits1(&s->gb);
510

    
511
    //only 2 formats possible
512
    if (format == 0){//QCIF
513
        s->width = 176;
514
        s->height = 144;
515
        s->mb_width = 11;
516
        s->mb_height = 9;
517
    }else{//CIF
518
        s->width = 352;
519
        s->height = 288;
520
        s->mb_width = 22;
521
        s->mb_height = 18;
522
    }
523

    
524
    s->mb_num = s->mb_width * s->mb_height;
525

    
526
    skip_bits1(&s->gb); /* still image mode off */
527
    skip_bits1(&s->gb); /* Reserved */
528

    
529
    /* PEI */
530
    while (get_bits1(&s->gb) != 0){
531
        skip_bits(&s->gb, 8);
532
    }
533

    
534
    // h261 has no I-FRAMES, but if we pass I_TYPE for the first frame, the codec crashes if it does 
535
    // not contain all I-blocks (e.g. when a packet is lost)
536
    s->pict_type = P_TYPE;
537

    
538
    h->gob_number = 0;
539
    return 0;
540
}
541

    
542
static int h261_decode_gob(H261Context *h){
543
    MpegEncContext * const s = &h->s;
544
    
545
    ff_set_qscale(s, s->qscale);
546

    
547
    /* decode mb's */
548
    while(h->current_mba <= MBA_STUFFING)
549
    {
550
        int ret;
551
        /* DCT & quantize */
552
        ret= h261_decode_mb(h);
553
        if(ret<0){
554
            if(ret==SLICE_END){
555
                h261_decode_mb_skipped(h, h->current_mba, 33);                
556
                return 0;
557
            }
558
            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
559
            return -1;
560
        }
561
        
562
        h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
563
    }
564
    
565
    return -1;
566
}
567

    
568
static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
569
    int vop_found, i, j, bits_left, last_bits;
570
    uint32_t state;
571

    
572
    H261Context *h = avctx->priv_data;
573

    
574
    if(h){
575
        bits_left = h->bits_left;
576
        last_bits = h->last_bits;
577
    }
578
    else{
579
        bits_left = 0;
580
        last_bits = 0;
581
    }
582

    
583
    vop_found= pc->frame_start_found;
584
    state= pc->state;
585
    if(bits_left!=0 && !vop_found)
586
        state = state << (8-bits_left) | last_bits;
587
    i=0;
588
    if(!vop_found){
589
        for(i=0; i<buf_size; i++){
590
            state= (state<<8) | buf[i];
591
            for(j=0; j<8; j++){
592
                if(( (  (state<<j)  |  (buf[i]>>(8-j))  )>>(32-20) == 0x10 )&&(((state >> (17-j)) & 0x4000) == 0x0)){
593
                    i++;
594
                    vop_found=1;
595
                    break;
596
                }
597
            }
598
            if(vop_found)
599
                    break;    
600
        }
601
    }
602
    if(vop_found){
603
        for(; i<buf_size; i++){
604
            if(avctx->flags & CODEC_FLAG_TRUNCATED)//XXX ffplay workaround, someone a better solution?
605
                state= (state<<8) | buf[i];
606
            for(j=0; j<8; j++){
607
                if(( (  (state<<j)  |  (buf[i]>>(8-j))  )>>(32-20) == 0x10 )&&(((state >> (17-j)) & 0x4000) == 0x0)){
608
                    pc->frame_start_found=0;
609
                    pc->state=-1;
610
                    return i-3;
611
                }
612
            }
613
        }
614
    }
615

    
616
    pc->frame_start_found= vop_found;
617
    pc->state= state;
618
    return END_NOT_FOUND;
619
}
620

    
621
static int h261_parse(AVCodecParserContext *s,
622
                      AVCodecContext *avctx,
623
                      uint8_t **poutbuf, int *poutbuf_size, 
624
                      const uint8_t *buf, int buf_size)
625
{
626
    ParseContext *pc = s->priv_data;
627
    int next;
628
    
629
    next= h261_find_frame_end(pc,avctx, buf, buf_size);
630
    if (ff_combine_frame(pc, next, (uint8_t **)&buf, &buf_size) < 0) {
631
        *poutbuf = NULL;
632
        *poutbuf_size = 0;
633
        return buf_size;
634
    }
635
    *poutbuf = (uint8_t *)buf;
636
    *poutbuf_size = buf_size;
637
    return next;
638
}
639

    
640
/**
641
 * returns the number of bytes consumed for building the current frame
642
 */
643
static int get_consumed_bytes(MpegEncContext *s, int buf_size){
644
    if(s->flags&CODEC_FLAG_TRUNCATED){
645
        int pos= (get_bits_count(&s->gb)+7)>>3;
646
        pos -= s->parse_context.last_index;
647
        if(pos<0) pos=0;// padding is not really read so this might be -1
648
        return pos;
649
    }else{
650
        int pos= get_bits_count(&s->gb)>>3;
651
        if(pos==0) pos=1; //avoid infinite loops (i doubt thats needed but ...)
652
        if(pos+10>buf_size) pos=buf_size; // oops ;)
653

    
654
        return pos;
655
    }
656
}
657

    
658
static int h261_decode_frame(AVCodecContext *avctx,
659
                             void *data, int *data_size,
660
                             uint8_t *buf, int buf_size)
661
{
662
    H261Context *h= avctx->priv_data;
663
    MpegEncContext *s = &h->s;
664
    int ret;
665
    AVFrame *pict = data;
666

    
667
#ifdef DEBUG
668
    printf("*****frame %d size=%d\n", avctx->frame_number, buf_size);
669
    printf("bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
670
#endif
671
    s->flags= avctx->flags;
672
    s->flags2= avctx->flags2;
673

    
674
    /* no supplementary picture */
675
    if (buf_size == 0) {
676
        return 0;
677
    }
678

    
679
    if(s->flags&CODEC_FLAG_TRUNCATED){
680
        int next;
681

    
682
        next= h261_find_frame_end(&s->parse_context,avctx, buf, buf_size);
683

    
684
        if( ff_combine_frame(&s->parse_context, next, &buf, &buf_size) < 0 )
685
            return buf_size;
686
    }
687

    
688

    
689
retry:
690

    
691
    init_get_bits(&s->gb, buf, buf_size*8);
692

    
693
    if(!s->context_initialized){
694
        if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
695
            return -1;
696
    }
697

    
698
    //we need to set current_picture_ptr before reading the header, otherwise we cant store anyting im there
699
    if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
700
        int i= ff_find_unused_picture(s, 0);
701
        s->current_picture_ptr= &s->picture[i];
702
    }
703

    
704
    ret = h261_decode_picture_header(h);
705

    
706
    /* skip if the header was thrashed */
707
    if (ret < 0){
708
        av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
709
        return -1;
710
    }
711

    
712
    if (s->width != avctx->coded_width || s->height != avctx->coded_height){
713
        ParseContext pc= s->parse_context; //FIXME move these demuxng hack to avformat
714
        s->parse_context.buffer=0;
715
        MPV_common_end(s);
716
        s->parse_context= pc;
717
    }
718
    if (!s->context_initialized) {
719
        avcodec_set_dimensions(avctx, s->width, s->height);
720

    
721
        goto retry;
722
    }
723

    
724
    // for hurry_up==5
725
    s->current_picture.pict_type= s->pict_type;
726
    s->current_picture.key_frame= s->pict_type == I_TYPE;
727

    
728
    /* skip everything if we are in a hurry>=5 */
729
    if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
730

    
731
    if(MPV_frame_start(s, avctx) < 0)
732
        return -1;
733

    
734
    ff_er_frame_start(s);
735

    
736
    /* decode each macroblock */
737
    s->mb_x=0;
738
    s->mb_y=0;
739

    
740
    while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
741
        if(ff_h261_resync(h)<0)
742
            break;
743
        h261_decode_gob(h);
744
    }
745
    MPV_frame_end(s);
746

    
747
assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
748
assert(s->current_picture.pict_type == s->pict_type);
749
    *pict= *(AVFrame*)&s->current_picture;
750
    ff_print_debug_info(s, pict);
751

    
752
    /* Return the Picture timestamp as the frame number */
753
    /* we substract 1 because it is added on utils.c    */
754
    avctx->frame_number = s->picture_number - 1;
755

    
756
    *data_size = sizeof(AVFrame);
757

    
758
    return get_consumed_bytes(s, buf_size);
759
}
760

    
761
static int h261_decode_end(AVCodecContext *avctx)
762
{
763
    H261Context *h= avctx->priv_data;
764
    MpegEncContext *s = &h->s;
765

    
766
    MPV_common_end(s);
767
    return 0;
768
}
769

    
770
AVCodec h261_decoder = {
771
    "h261",
772
    CODEC_TYPE_VIDEO,
773
    CODEC_ID_H261,
774
    sizeof(H261Context),
775
    h261_decode_init,
776
    NULL,
777
    h261_decode_end,
778
    h261_decode_frame,
779
    CODEC_CAP_TRUNCATED,
780
};
781

    
782
AVCodecParser h261_parser = {
783
    { CODEC_ID_H261 },
784
    sizeof(ParseContext),
785
    NULL,
786
    h261_parse,
787
    ff_parse_close,
788
};