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ffmpeg / libavcodec / h261.c @ 5bbad3eb

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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 previous_mba;
51
    int mba_diff;
52
    int mtype;
53
    int current_mv_x;
54
    int current_mv_y;
55
    int gob_number;
56
    int bits_left; //8 - nr of bits left of the following frame in the last byte in this frame
57
    int last_bits; //bits left of the following frame in the last byte in this frame
58
    int gob_start_code_skipped; // 1 if gob start code is already read before gob header is read
59
}H261Context;
60

    
61
void ff_h261_loop_filter(MpegEncContext *s){
62
    H261Context * h= (H261Context*)s;
63
    const int linesize  = s->linesize;
64
    const int uvlinesize= s->uvlinesize;
65
    uint8_t *dest_y = s->dest[0];
66
    uint8_t *dest_cb= s->dest[1];
67
    uint8_t *dest_cr= s->dest[2];
68

    
69
    if(!(IS_FIL (h->mtype)))
70
        return;
71

    
72
    s->dsp.h261_loop_filter(dest_y                   , linesize);
73
    s->dsp.h261_loop_filter(dest_y                + 8, linesize);
74
    s->dsp.h261_loop_filter(dest_y + 8 * linesize    , linesize);
75
    s->dsp.h261_loop_filter(dest_y + 8 * linesize + 8, linesize);
76
    s->dsp.h261_loop_filter(dest_cb, uvlinesize);
77
    s->dsp.h261_loop_filter(dest_cr, uvlinesize);
78
}
79

    
80
static int ff_h261_get_picture_format(int width, int height){
81
    // QCIF
82
    if (width == 176 && height == 144)
83
        return 0;
84
    // CIF
85
    else if (width == 352 && height == 288)
86
        return 1;
87
    // ERROR
88
    else
89
        return -1;
90
}
91

    
92
static void h261_encode_block(H261Context * h, DCTELEM * block,
93
                              int n);
94
static int h261_decode_block(H261Context *h, DCTELEM *block,
95
                             int n, int coded);
96

    
97
void ff_h261_encode_picture_header(MpegEncContext * s, int picture_number){
98
    H261Context * h = (H261Context *) s;
99
    int format, temp_ref;
100

    
101
    align_put_bits(&s->pb);
102

    
103
    /* Update the pointer to last GOB */
104
    s->ptr_lastgob = pbBufPtr(&s->pb);
105

    
106
    put_bits(&s->pb, 20, 0x10); /* PSC */
107

    
108
    temp_ref= s->picture_number * (int64_t)30000 * s->avctx->frame_rate_base / 
109
                         (1001 * (int64_t)s->avctx->frame_rate);
110
    put_bits(&s->pb, 5, temp_ref & 0x1f); /* TemporalReference */
111

    
112
    put_bits(&s->pb, 1, 0); /* split screen off */
113
    put_bits(&s->pb, 1, 0); /* camera  off */
114
    put_bits(&s->pb, 1, 0); /* freeze picture release off */
115
    
116
    format = ff_h261_get_picture_format(s->width, s->height);
117
    
118
    put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
119

    
120
    put_bits(&s->pb, 1, 0); /* still image mode */
121
    put_bits(&s->pb, 1, 0); /* reserved */
122

    
123
    put_bits(&s->pb, 1, 0); /* no PEI */    
124
    if(format == 0)
125
        h->gob_number = -1;
126
    else
127
        h->gob_number = 0;
128
    h->current_mba = 0;
129
}
130

    
131
/**
132
 * Encodes a group of blocks header.
133
 */
134
static void h261_encode_gob_header(MpegEncContext * s, int mb_line){
135
    H261Context * h = (H261Context *)s;
136
    if(ff_h261_get_picture_format(s->width, s->height) == 0){
137
        h->gob_number+=2; // QCIF
138
    }
139
    else{
140
        h->gob_number++; // CIF
141
    }
142
    put_bits(&s->pb, 16, 1); /* GBSC */
143
    put_bits(&s->pb, 4, h->gob_number); /* GN */
144
    put_bits(&s->pb, 5, s->qscale); /* GQUANT */
145
    put_bits(&s->pb, 1, 0); /* no GEI */
146
    h->current_mba = 0;
147
    h->previous_mba = 0;
148
    h->current_mv_x=0;
149
    h->current_mv_y=0;
150
}
151

    
152
void ff_h261_reorder_mb_index(MpegEncContext* s){
153
    int index= s->mb_x + s->mb_y*s->mb_width;
154

    
155
    if(index % 33 == 0)
156
        h261_encode_gob_header(s,0);
157

    
158
    /* for CIF the GOB's are fragmented in the middle of a scanline
159
       that's why we need to adjust the x and y index of the macroblocks */
160
    if(ff_h261_get_picture_format(s->width,s->height) == 1){ // CIF
161
        s->mb_x =     index % 11 ; index /= 11;
162
        s->mb_y =     index %  3 ; index /=  3;
163
        s->mb_x+= 11*(index %  2); index /=  2;
164
        s->mb_y+=  3*index;
165
        
166
        ff_init_block_index(s);
167
        ff_update_block_index(s);
168
    }
169
}
170

    
171
static void h261_encode_motion(H261Context * h, int val){
172
    MpegEncContext * const s = &h->s;
173
    int sign, code;
174
    if(val==0){
175
        code = 0;
176
        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
177
    } 
178
    else{
179
        if(val > 16)
180
            val -=32;
181
        if(val < -16)
182
            val+=32;
183
        sign = val < 0;
184
        code = sign ? -val : val; 
185
        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
186
        put_bits(&s->pb,1,sign);
187
    }
188
}
189

    
190
static inline int get_cbp(MpegEncContext * s,
191
                      DCTELEM block[6][64])
192
{
193
    int i, cbp;
194
    cbp= 0;
195
    for (i = 0; i < 6; i++) {
196
        if (s->block_last_index[i] >= 0)
197
            cbp |= 1 << (5 - i);
198
    }
199
    return cbp;
200
}
201
void ff_h261_encode_mb(MpegEncContext * s,
202
         DCTELEM block[6][64],
203
         int motion_x, int motion_y)
204
{
205
    H261Context * h = (H261Context *)s;
206
    int mvd, mv_diff_x, mv_diff_y, i, cbp;
207
    cbp = 63; // avoid warning
208
    mvd = 0;
209
 
210
    h->current_mba++;
211
    h->mtype = 0;
212
 
213
    if (!s->mb_intra){
214
        /* compute cbp */
215
        cbp= get_cbp(s, block);
216
   
217
        /* mvd indicates if this block is motion compensated */
218
        mvd = motion_x | motion_y;
219

    
220
        if((cbp | mvd | s->dquant ) == 0) {
221
            /* skip macroblock */
222
            s->skip_count++;
223
            h->current_mv_x=0;
224
            h->current_mv_y=0;
225
            return;
226
        }
227
    }
228

    
229
    /* MB is not skipped, encode MBA */
230
    put_bits(&s->pb, h261_mba_bits[(h->current_mba-h->previous_mba)-1], h261_mba_code[(h->current_mba-h->previous_mba)-1]);
231
 
232
    /* calculate MTYPE */
233
    if(!s->mb_intra){
234
        h->mtype++;
235
        
236
        if(mvd || s->loop_filter)
237
            h->mtype+=3;
238
        if(s->loop_filter)
239
            h->mtype+=3;
240
        if(cbp || s->dquant)
241
            h->mtype++;
242
        assert(h->mtype > 1);
243
    }
244

    
245
    if(s->dquant) 
246
        h->mtype++;
247

    
248
    put_bits(&s->pb, h261_mtype_bits[h->mtype], h261_mtype_code[h->mtype]);
249
 
250
    h->mtype = h261_mtype_map[h->mtype];
251
 
252
    if(IS_QUANT(h->mtype)){
253
        ff_set_qscale(s,s->qscale+s->dquant);
254
        put_bits(&s->pb, 5, s->qscale);
255
    }
256
 
257
    if(IS_16X16(h->mtype)){
258
        mv_diff_x = (motion_x >> 1) - h->current_mv_x;
259
        mv_diff_y = (motion_y >> 1) - h->current_mv_y;
260
        h->current_mv_x = (motion_x >> 1);
261
        h->current_mv_y = (motion_y >> 1);
262
        h261_encode_motion(h,mv_diff_x);
263
        h261_encode_motion(h,mv_diff_y);
264
    }
265
 
266
    h->previous_mba = h->current_mba;
267
 
268
    if(HAS_CBP(h->mtype)){
269
        put_bits(&s->pb,h261_cbp_tab[cbp-1][1],h261_cbp_tab[cbp-1][0]); 
270
    }
271
    for(i=0; i<6; i++) {
272
        /* encode each block */
273
        h261_encode_block(h, block[i], i);
274
    }
275

    
276
    if ( ( h->current_mba == 11 ) || ( h->current_mba == 22 ) || ( h->current_mba == 33 ) || ( !IS_16X16 ( h->mtype ) )){
277
        h->current_mv_x=0;
278
        h->current_mv_y=0;
279
    }
280
}
281

    
282
void ff_h261_encode_init(MpegEncContext *s){
283
    static int done = 0;
284
    
285
    if (!done) {
286
        done = 1;
287
        init_rl(&h261_rl_tcoeff);
288
    }
289

    
290
    s->min_qcoeff= -127;
291
    s->max_qcoeff=  127;
292
    s->y_dc_scale_table=
293
    s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
294
}
295

    
296

    
297
/**
298
 * encodes a 8x8 block.
299
 * @param block the 8x8 block
300
 * @param n block index (0-3 are luma, 4-5 are chroma)
301
 */
302
static void h261_encode_block(H261Context * h, DCTELEM * block, int n){
303
    MpegEncContext * const s = &h->s;
304
    int level, run, last, i, j, last_index, last_non_zero, sign, slevel, code;
305
    RLTable *rl;
306

    
307
    rl = &h261_rl_tcoeff;
308
    if (s->mb_intra) {
309
        /* DC coef */
310
        level = block[0];
311
        /* 255 cannot be represented, so we clamp */
312
        if (level > 254) {
313
            level = 254;
314
            block[0] = 254;
315
        }
316
        /* 0 cannot be represented also */
317
        else if (level < 1) {
318
            level = 1;
319
            block[0] = 1;
320
        }
321
        if (level == 128)
322
            put_bits(&s->pb, 8, 0xff);
323
        else
324
            put_bits(&s->pb, 8, level);
325
        i = 1;
326
    } else if((block[0]==1 || block[0] == -1) && (s->block_last_index[n] > -1)){
327
        //special case
328
        put_bits(&s->pb,2,block[0]>0 ? 2 : 3 );
329
        i = 1;
330
    } else {
331
        i = 0;
332
    }
333
   
334
    /* AC coefs */
335
    last_index = s->block_last_index[n];
336
    last_non_zero = i - 1;
337
    for (; i <= last_index; i++) {
338
        j = s->intra_scantable.permutated[i];
339
        level = block[j];
340
        if (level) {
341
            run = i - last_non_zero - 1;
342
            last = (i == last_index);
343
            sign = 0;
344
            slevel = level;
345
            if (level < 0) {
346
                sign = 1;
347
                level = -level;
348
            }
349
            code = get_rl_index(rl, 0 /*no last in H.261, EOB is used*/, run, level);
350
            if(run==0 && level < 16)
351
            code+=1;
352
            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
353
            if (code == rl->n) {
354
                put_bits(&s->pb, 6, run);
355
                assert(slevel != 0);
356
                assert(level <= 127);
357
                put_bits(&s->pb, 8, slevel & 0xff);
358
            } else {
359
                put_bits(&s->pb, 1, sign);
360
            }
361
            last_non_zero = i;
362
        }
363
    }
364
    if(last_index > -1){
365
        put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]);// END OF BLOCK
366
    }
367
}
368

    
369
/***********************************************/
370
/* decoding */
371

    
372
static VLC h261_mba_vlc;
373
static VLC h261_mtype_vlc;
374
static VLC h261_mv_vlc;
375
static VLC h261_cbp_vlc;
376

    
377
void init_vlc_rl(RLTable *rl);
378

    
379
static void h261_decode_init_vlc(H261Context *h){
380
    static int done = 0;
381

    
382
    if(!done){
383
        done = 1;
384
        init_vlc(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
385
                 h261_mba_bits, 1, 1,
386
                 h261_mba_code, 1, 1);
387
        init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
388
                 h261_mtype_bits, 1, 1,
389
                 h261_mtype_code, 1, 1);
390
        init_vlc(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
391
                 &h261_mv_tab[0][1], 2, 1,
392
                 &h261_mv_tab[0][0], 2, 1);
393
        init_vlc(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
394
                 &h261_cbp_tab[0][1], 2, 1,
395
                 &h261_cbp_tab[0][0], 2, 1);
396
        init_rl(&h261_rl_tcoeff);
397
        init_vlc_rl(&h261_rl_tcoeff);
398
    }
399
}
400

    
401
static int h261_decode_init(AVCodecContext *avctx){
402
    H261Context *h= avctx->priv_data;
403
    MpegEncContext * const s = &h->s;
404

    
405
    // set defaults
406
    MPV_decode_defaults(s);
407
    s->avctx = avctx;
408

    
409
    s->width  = s->avctx->coded_width;
410
    s->height = s->avctx->coded_height;
411
    s->codec_id = s->avctx->codec->id;
412

    
413
    s->out_format = FMT_H261;
414
    s->low_delay= 1;
415
    avctx->pix_fmt= PIX_FMT_YUV420P;
416

    
417
    s->codec_id= avctx->codec->id;
418

    
419
    h261_decode_init_vlc(h);
420

    
421
    h->gob_start_code_skipped = 0;
422
    
423
    return 0;
424
}
425

    
426
/**
427
 * decodes the group of blocks header or slice header.
428
 * @return <0 if an error occured
429
 */
430
static int h261_decode_gob_header(H261Context *h){
431
    unsigned int val;
432
    MpegEncContext * const s = &h->s;
433
    
434
    if ( !h->gob_start_code_skipped ){
435
        /* Check for GOB Start Code */
436
        val = show_bits(&s->gb, 15);
437
        if(val)
438
            return -1;
439

    
440
        /* We have a GBSC */
441
        skip_bits(&s->gb, 16);
442
    }
443

    
444
    h->gob_start_code_skipped = 0;
445

    
446
    h->gob_number = get_bits(&s->gb, 4); /* GN */
447
    s->qscale = get_bits(&s->gb, 5); /* GQUANT */
448

    
449
    /* Check if gob_number is valid */
450
    if (s->mb_height==18){ //cif
451
        if ((h->gob_number<=0) || (h->gob_number>12))
452
            return -1;
453
    }
454
    else{ //qcif
455
        if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
456
            return -1;
457
    }
458

    
459
    /* GEI */
460
    while (get_bits1(&s->gb) != 0) {
461
        skip_bits(&s->gb, 8);
462
    }
463

    
464
    if(s->qscale==0)
465
        return -1;
466

    
467
    // For the first transmitted macroblock in a GOB, MBA is the absolute address. For
468
    // subsequent macroblocks, MBA is the difference between the absolute addresses of
469
    // the macroblock and the last transmitted macroblock.
470
    h->current_mba = 0;
471
    h->mba_diff = 0;
472

    
473
    return 0;
474
}
475

    
476
/**
477
 * decodes the group of blocks / video packet header.
478
 * @return <0 if no resync found
479
 */
480
static int ff_h261_resync(H261Context *h){
481
    MpegEncContext * const s = &h->s;
482
    int left, ret;
483

    
484
    if ( h->gob_start_code_skipped ){
485
        ret= h261_decode_gob_header(h);
486
        if(ret>=0)
487
            return 0;
488
    }
489
    else{
490
        if(show_bits(&s->gb, 15)==0){
491
            ret= h261_decode_gob_header(h);
492
            if(ret>=0)
493
                return 0;
494
        }
495
        //ok, its not where its supposed to be ...
496
        s->gb= s->last_resync_gb;
497
        align_get_bits(&s->gb);
498
        left= s->gb.size_in_bits - get_bits_count(&s->gb);
499

    
500
        for(;left>15+1+4+5; left-=8){
501
            if(show_bits(&s->gb, 15)==0){
502
                GetBitContext bak= s->gb;
503

    
504
                ret= h261_decode_gob_header(h);
505
                if(ret>=0)
506
                    return 0;
507

    
508
                s->gb= bak;
509
            }
510
            skip_bits(&s->gb, 8);
511
        }
512
    }
513

    
514
    return -1;
515
}
516

    
517
/**
518
 * decodes skipped macroblocks
519
 * @return 0
520
 */
521
static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
522
{
523
    MpegEncContext * const s = &h->s;
524
    int i;
525
    
526
    s->mb_intra = 0;
527

    
528
    for(i=mba1; i<mba2; i++){
529
        int j, xy;
530

    
531
        s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
532
        s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
533
        xy = s->mb_x + s->mb_y * s->mb_stride;
534
        ff_init_block_index(s);
535
        ff_update_block_index(s);
536
        s->dsp.clear_blocks(s->block[0]);
537

    
538
        for(j=0;j<6;j++)
539
            s->block_last_index[j] = -1;
540

    
541
        s->mv_dir = MV_DIR_FORWARD;
542
        s->mv_type = MV_TYPE_16X16;
543
        s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
544
        s->mv[0][0][0] = 0;
545
        s->mv[0][0][1] = 0;
546
        s->mb_skiped = 1;
547
        h->mtype &= ~MB_TYPE_H261_FIL;
548

    
549
        MPV_decode_mb(s, s->block);
550
    }
551

    
552
    return 0;
553
}
554

    
555
static int decode_mv_component(GetBitContext *gb, int v){
556
    int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
557

    
558
    /* check if mv_diff is valid */
559
    if ( mv_diff < 0 )
560
        return v;
561

    
562
    mv_diff = mvmap[mv_diff];
563

    
564
    if(mv_diff && !get_bits1(gb))
565
        mv_diff= -mv_diff;
566
    
567
    v += mv_diff;
568
    if     (v <=-16) v+= 32;
569
    else if(v >= 16) v-= 32;
570

    
571
    return v;
572
}
573

    
574
static int h261_decode_mb(H261Context *h){
575
    MpegEncContext * const s = &h->s;
576
    int i, cbp, xy;
577

    
578
    cbp = 63;
579
    // Read mba
580
    do{
581
        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
582

    
583
        /* Check for slice end */
584
        /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
585
        if (h->mba_diff == MBA_STARTCODE){ // start code
586
            h->gob_start_code_skipped = 1;
587
            return SLICE_END;
588
        }
589
    }
590
    while( h->mba_diff == MBA_STUFFING ); // stuffing
591

    
592
    if ( h->mba_diff < 0 ){
593
        if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
594
            return SLICE_END;
595

    
596
        av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
597
        return SLICE_ERROR;
598
    }
599

    
600
    h->mba_diff += 1;
601
    h->current_mba += h->mba_diff;
602

    
603
    if ( h->current_mba > MBA_STUFFING )
604
        return SLICE_ERROR;
605
    
606
    s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
607
    s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
608
    xy = s->mb_x + s->mb_y * s->mb_stride;
609
    ff_init_block_index(s);
610
    ff_update_block_index(s);
611
    s->dsp.clear_blocks(s->block[0]);
612

    
613
    // Read mtype
614
    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
615
    h->mtype = h261_mtype_map[h->mtype];
616

    
617
    // Read mquant
618
    if ( IS_QUANT ( h->mtype ) ){
619
        ff_set_qscale(s, get_bits(&s->gb, 5));
620
    }
621

    
622
    s->mb_intra = IS_INTRA4x4(h->mtype);
623

    
624
    // Read mv
625
    if ( IS_16X16 ( h->mtype ) ){
626
        // Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the
627
        // vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the
628
        // following three situations:
629
        // 1) evaluating MVD for macroblocks 1, 12 and 23;
630
        // 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
631
        // 3) MTYPE of the previous macroblock was not MC.
632
        if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) ||
633
             ( h->mba_diff != 1))
634
        {
635
            h->current_mv_x = 0;
636
            h->current_mv_y = 0;
637
        }
638

    
639
        h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
640
        h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
641
    }else{
642
        h->current_mv_x = 0;
643
        h->current_mv_y = 0;
644
    }
645

    
646
    // Read cbp
647
    if ( HAS_CBP( h->mtype ) ){
648
        cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
649
    }
650

    
651
    if(s->mb_intra){
652
        s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
653
        goto intra;
654
    }
655

    
656
    //set motion vectors
657
    s->mv_dir = MV_DIR_FORWARD;
658
    s->mv_type = MV_TYPE_16X16;
659
    s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
660
    s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation
661
    s->mv[0][0][1] = h->current_mv_y * 2;
662

    
663
intra:
664
    /* decode each block */
665
    if(s->mb_intra || HAS_CBP(h->mtype)){
666
        for (i = 0; i < 6; i++) {
667
            if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
668
                return SLICE_ERROR;
669
            }
670
            cbp+=cbp;
671
        }
672
    }
673

    
674
    MPV_decode_mb(s, s->block);
675

    
676
    return SLICE_OK;
677
}
678

    
679
/**
680
 * decodes a macroblock
681
 * @return <0 if an error occured
682
 */
683
static int h261_decode_block(H261Context * h, DCTELEM * block,
684
                             int n, int coded)
685
{
686
    MpegEncContext * const s = &h->s;
687
    int code, level, i, j, run;
688
    RLTable *rl = &h261_rl_tcoeff;
689
    const uint8_t *scan_table;
690
    
691
    // For the variable length encoding there are two code tables, one being used for
692
    // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
693
    // for all other LEVELs except the first one in INTRA blocks which is fixed length
694
    // coded with 8 bits.
695
    // NOTE: the two code tables only differ in one VLC so we handle that manually.
696
    scan_table = s->intra_scantable.permutated;
697
    if (s->mb_intra){
698
        /* DC coef */
699
        level = get_bits(&s->gb, 8);
700
        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
701
        if((level&0x7F) == 0){
702
            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
703
            return -1;
704
        }
705
        // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
706
        if (level == 255)
707
            level = 128;
708
        block[0] = level;
709
        i = 1;
710
    }else if(coded){
711
        // Run  Level   Code
712
        // EOB                  Not possible for first level when cbp is available (that's why the table is different)
713
        // 0    1               1s
714
        // *    *               0*
715
        int check = show_bits(&s->gb, 2);
716
        i = 0;
717
        if ( check & 0x2 ){
718
            skip_bits(&s->gb, 2);
719
            block[0] = ( check & 0x1 ) ? -1 : 1;
720
            i = 1;
721
        }
722
    }else{
723
        i = 0;
724
    }
725
    if(!coded){
726
        s->block_last_index[n] = i - 1;
727
        return 0;
728
    }
729
    for(;;){
730
        code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
731
        if (code < 0){
732
            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
733
            return -1;
734
        }
735
        if (code == rl->n) {
736
            /* escape */
737
            // 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.
738
            run = get_bits(&s->gb, 6);
739
            level = get_sbits(&s->gb, 8);
740
        }else if(code == 0){
741
            break;
742
        }else{
743
            run = rl->table_run[code];
744
            level = rl->table_level[code];
745
            if (get_bits1(&s->gb))
746
                level = -level;
747
        }
748
        i += run;
749
        if (i >= 64){
750
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
751
            return -1;
752
        }
753
        j = scan_table[i];
754
        block[j] = level;
755
        i++;
756
    }
757
    s->block_last_index[n] = i-1;
758
    return 0;
759
}
760

    
761
/**
762
 * decodes the H261 picture header.
763
 * @return <0 if no startcode found
764
 */
765
int h261_decode_picture_header(H261Context *h){
766
    MpegEncContext * const s = &h->s;
767
    int format, i;
768
    uint32_t startcode= 0;
769

    
770
    for(i= s->gb.size_in_bits - get_bits_count(&s->gb); i>24; i-=1){
771
        startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
772

    
773
        if(startcode == 0x10)
774
            break;
775
    }
776

    
777
    if (startcode != 0x10){
778
        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
779
        return -1;
780
    }
781

    
782
    /* temporal reference */
783
    s->picture_number = get_bits(&s->gb, 5); /* picture timestamp */
784

    
785
    /* PTYPE starts here */
786
    skip_bits1(&s->gb); /* split screen off */
787
    skip_bits1(&s->gb); /* camera  off */
788
    skip_bits1(&s->gb); /* freeze picture release off */
789

    
790
    format = get_bits1(&s->gb);
791

    
792
    //only 2 formats possible
793
    if (format == 0){//QCIF
794
        s->width = 176;
795
        s->height = 144;
796
        s->mb_width = 11;
797
        s->mb_height = 9;
798
    }else{//CIF
799
        s->width = 352;
800
        s->height = 288;
801
        s->mb_width = 22;
802
        s->mb_height = 18;
803
    }
804

    
805
    s->mb_num = s->mb_width * s->mb_height;
806

    
807
    skip_bits1(&s->gb); /* still image mode off */
808
    skip_bits1(&s->gb); /* Reserved */
809

    
810
    /* PEI */
811
    while (get_bits1(&s->gb) != 0){
812
        skip_bits(&s->gb, 8);
813
    }
814

    
815
    // h261 has no I-FRAMES, but if we pass I_TYPE for the first frame, the codec crashes if it does 
816
    // not contain all I-blocks (e.g. when a packet is lost)
817
    s->pict_type = P_TYPE;
818

    
819
    h->gob_number = 0;
820
    return 0;
821
}
822

    
823
static int h261_decode_gob(H261Context *h){
824
    MpegEncContext * const s = &h->s;
825
    
826
    ff_set_qscale(s, s->qscale);
827

    
828
    /* decode mb's */
829
    while(h->current_mba <= MBA_STUFFING)
830
    {
831
        int ret;
832
        /* DCT & quantize */
833
        ret= h261_decode_mb(h);
834
        if(ret<0){
835
            if(ret==SLICE_END){
836
                h261_decode_mb_skipped(h, h->current_mba, 33);                
837
                return 0;
838
            }
839
            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
840
            return -1;
841
        }
842
        
843
        h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
844
    }
845
    
846
    return -1;
847
}
848

    
849
static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
850
    int vop_found, i, j, bits_left, last_bits;
851
    uint32_t state;
852

    
853
    H261Context *h = avctx->priv_data;
854

    
855
    if(h){
856
        bits_left = h->bits_left;
857
        last_bits = h->last_bits;
858
    }
859
    else{
860
        bits_left = 0;
861
        last_bits = 0;
862
    }
863

    
864
    vop_found= pc->frame_start_found;
865
    state= pc->state;
866
    if(bits_left!=0 && !vop_found)
867
        state = state << (8-bits_left) | last_bits;
868
    i=0;
869
    if(!vop_found){
870
        for(i=0; i<buf_size; i++){
871
            state= (state<<8) | buf[i];
872
            for(j=0; j<8; j++){
873
                if(( (  (state<<j)  |  (buf[i]>>(8-j))  )>>(32-20) == 0x10 )&&(((state >> (17-j)) & 0x4000) == 0x0)){
874
                    i++;
875
                    vop_found=1;
876
                    break;
877
                }
878
            }
879
            if(vop_found)
880
                    break;    
881
        }
882
    }
883
    if(vop_found){
884
        for(; i<buf_size; i++){
885
            if(avctx->flags & CODEC_FLAG_TRUNCATED)//XXX ffplay workaround, someone a better solution?
886
                state= (state<<8) | buf[i];
887
            for(j=0; j<8; j++){
888
                if(( (  (state<<j)  |  (buf[i]>>(8-j))  )>>(32-20) == 0x10 )&&(((state >> (17-j)) & 0x4000) == 0x0)){
889
                    pc->frame_start_found=0;
890
                    pc->state=-1;
891
                    return i-3;
892
                }
893
            }
894
        }
895
    }
896

    
897
    pc->frame_start_found= vop_found;
898
    pc->state= state;
899
    return END_NOT_FOUND;
900
}
901

    
902
static int h261_parse(AVCodecParserContext *s,
903
                      AVCodecContext *avctx,
904
                      uint8_t **poutbuf, int *poutbuf_size, 
905
                      const uint8_t *buf, int buf_size)
906
{
907
    ParseContext *pc = s->priv_data;
908
    int next;
909
    
910
    next= h261_find_frame_end(pc,avctx, buf, buf_size);
911
    if (ff_combine_frame(pc, next, (uint8_t **)&buf, &buf_size) < 0) {
912
        *poutbuf = NULL;
913
        *poutbuf_size = 0;
914
        return buf_size;
915
    }
916
    *poutbuf = (uint8_t *)buf;
917
    *poutbuf_size = buf_size;
918
    return next;
919
}
920

    
921
/**
922
 * returns the number of bytes consumed for building the current frame
923
 */
924
static int get_consumed_bytes(MpegEncContext *s, int buf_size){
925
    if(s->flags&CODEC_FLAG_TRUNCATED){
926
        int pos= (get_bits_count(&s->gb)+7)>>3;
927
        pos -= s->parse_context.last_index;
928
        if(pos<0) pos=0;// padding is not really read so this might be -1
929
        return pos;
930
    }else{
931
        int pos= get_bits_count(&s->gb)>>3;
932
        if(pos==0) pos=1; //avoid infinite loops (i doubt thats needed but ...)
933
        if(pos+10>buf_size) pos=buf_size; // oops ;)
934

    
935
        return pos;
936
    }
937
}
938

    
939
static int h261_decode_frame(AVCodecContext *avctx,
940
                             void *data, int *data_size,
941
                             uint8_t *buf, int buf_size)
942
{
943
    H261Context *h= avctx->priv_data;
944
    MpegEncContext *s = &h->s;
945
    int ret;
946
    AVFrame *pict = data;
947

    
948
#ifdef DEBUG
949
    printf("*****frame %d size=%d\n", avctx->frame_number, buf_size);
950
    printf("bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
951
#endif
952
    s->flags= avctx->flags;
953
    s->flags2= avctx->flags2;
954

    
955
    /* no supplementary picture */
956
    if (buf_size == 0) {
957
        return 0;
958
    }
959

    
960
    if(s->flags&CODEC_FLAG_TRUNCATED){
961
        int next;
962

    
963
        next= h261_find_frame_end(&s->parse_context,avctx, buf, buf_size);
964

    
965
        if( ff_combine_frame(&s->parse_context, next, &buf, &buf_size) < 0 )
966
            return buf_size;
967
    }
968

    
969

    
970
retry:
971

    
972
    init_get_bits(&s->gb, buf, buf_size*8);
973

    
974
    if(!s->context_initialized){
975
        if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
976
            return -1;
977
    }
978

    
979
    //we need to set current_picture_ptr before reading the header, otherwise we cant store anyting im there
980
    if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
981
        int i= ff_find_unused_picture(s, 0);
982
        s->current_picture_ptr= &s->picture[i];
983
    }
984

    
985
    ret = h261_decode_picture_header(h);
986

    
987
    /* skip if the header was thrashed */
988
    if (ret < 0){
989
        av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
990
        return -1;
991
    }
992

    
993
    if (s->width != avctx->coded_width || s->height != avctx->coded_height){
994
        ParseContext pc= s->parse_context; //FIXME move these demuxng hack to avformat
995
        s->parse_context.buffer=0;
996
        MPV_common_end(s);
997
        s->parse_context= pc;
998
    }
999
    if (!s->context_initialized) {
1000
        avcodec_set_dimensions(avctx, s->width, s->height);
1001

    
1002
        goto retry;
1003
    }
1004

    
1005
    // for hurry_up==5
1006
    s->current_picture.pict_type= s->pict_type;
1007
    s->current_picture.key_frame= s->pict_type == I_TYPE;
1008

    
1009
    /* skip everything if we are in a hurry>=5 */
1010
    if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
1011

    
1012
    if(MPV_frame_start(s, avctx) < 0)
1013
        return -1;
1014

    
1015
    ff_er_frame_start(s);
1016

    
1017
    /* decode each macroblock */
1018
    s->mb_x=0;
1019
    s->mb_y=0;
1020

    
1021
    while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
1022
        if(ff_h261_resync(h)<0)
1023
            break;
1024
        h261_decode_gob(h);
1025
    }
1026
    MPV_frame_end(s);
1027

    
1028
assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
1029
assert(s->current_picture.pict_type == s->pict_type);
1030
    *pict= *(AVFrame*)&s->current_picture;
1031
    ff_print_debug_info(s, pict);
1032

    
1033
    /* Return the Picture timestamp as the frame number */
1034
    /* we substract 1 because it is added on utils.c    */
1035
    avctx->frame_number = s->picture_number - 1;
1036

    
1037
    *data_size = sizeof(AVFrame);
1038

    
1039
    return get_consumed_bytes(s, buf_size);
1040
}
1041

    
1042
static int h261_decode_end(AVCodecContext *avctx)
1043
{
1044
    H261Context *h= avctx->priv_data;
1045
    MpegEncContext *s = &h->s;
1046

    
1047
    MPV_common_end(s);
1048
    return 0;
1049
}
1050

    
1051
AVCodec h261_encoder = {
1052
    "h261",
1053
    CODEC_TYPE_VIDEO,
1054
    CODEC_ID_H261,
1055
    sizeof(H261Context),
1056
    MPV_encode_init,
1057
    MPV_encode_picture,
1058
    MPV_encode_end,
1059
};
1060

    
1061
AVCodec h261_decoder = {
1062
    "h261",
1063
    CODEC_TYPE_VIDEO,
1064
    CODEC_ID_H261,
1065
    sizeof(H261Context),
1066
    h261_decode_init,
1067
    NULL,
1068
    h261_decode_end,
1069
    h261_decode_frame,
1070
    CODEC_CAP_TRUNCATED,
1071
};
1072

    
1073
AVCodecParser h261_parser = {
1074
    { CODEC_ID_H261 },
1075
    sizeof(ParseContext),
1076
    NULL,
1077
    h261_parse,
1078
    ff_parse_close,
1079
};