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ffmpeg / libavcodec / h261.c @ 2029f312

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1
/*
2
 * H261 decoder
3
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
4
 * Copyright (c) 2004 Maarten Daniels
5
 *
6
 * This file is part of FFmpeg.
7
 *
8
 * FFmpeg is free software; you can redistribute it and/or
9
 * modify it under the terms of the GNU Lesser General Public
10
 * License as published by the Free Software Foundation; either
11
 * version 2.1 of the License, or (at your option) any later version.
12
 *
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 * FFmpeg is distributed in the hope that it will be useful,
14
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
22

    
23
/**
24
 * @file h261.c
25
 * h261codec.
26
 */
27

    
28
#include "dsputil.h"
29
#include "avcodec.h"
30
#include "mpegvideo.h"
31
#include "h261data.h"
32

    
33

    
34
#define H261_MBA_VLC_BITS 9
35
#define H261_MTYPE_VLC_BITS 6
36
#define H261_MV_VLC_BITS 7
37
#define H261_CBP_VLC_BITS 9
38
#define TCOEFF_VLC_BITS 9
39

    
40
#define MBA_STUFFING 33
41
#define MBA_STARTCODE 34
42
#define IS_FIL(a)    ((a)&MB_TYPE_H261_FIL)
43

    
44
/**
45
 * H261Context
46
 */
47
typedef struct H261Context{
48
    MpegEncContext s;
49

    
50
    int current_mba;
51
    int previous_mba;
52
    int mba_diff;
53
    int mtype;
54
    int current_mv_x;
55
    int current_mv_y;
56
    int gob_number;
57
    int gob_start_code_skipped; // 1 if gob start code is already read before gob header is read
58
}H261Context;
59

    
60
static uint8_t static_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
61

    
62
void ff_h261_loop_filter(MpegEncContext *s){
63
    H261Context * h= (H261Context*)s;
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    const int linesize  = s->linesize;
65
    const int uvlinesize= s->uvlinesize;
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    uint8_t *dest_y = s->dest[0];
67
    uint8_t *dest_cb= s->dest[1];
68
    uint8_t *dest_cr= s->dest[2];
69

    
70
    if(!(IS_FIL (h->mtype)))
71
        return;
72

    
73
    s->dsp.h261_loop_filter(dest_y                   , linesize);
74
    s->dsp.h261_loop_filter(dest_y                + 8, linesize);
75
    s->dsp.h261_loop_filter(dest_y + 8 * linesize    , linesize);
76
    s->dsp.h261_loop_filter(dest_y + 8 * linesize + 8, linesize);
77
    s->dsp.h261_loop_filter(dest_cb, uvlinesize);
78
    s->dsp.h261_loop_filter(dest_cr, uvlinesize);
79
}
80

    
81
int ff_h261_get_picture_format(int width, int height){
82
    // QCIF
83
    if (width == 176 && height == 144)
84
        return 0;
85
    // CIF
86
    else if (width == 352 && height == 288)
87
        return 1;
88
    // ERROR
89
    else
90
        return -1;
91
}
92

    
93
static void h261_encode_block(H261Context * h, DCTELEM * block,
94
                              int n);
95
static int h261_decode_block(H261Context *h, DCTELEM *block,
96
                             int n, int coded);
97

    
98
void ff_h261_encode_picture_header(MpegEncContext * s, int picture_number){
99
    H261Context * h = (H261Context *) s;
100
    int format, temp_ref;
101

    
102
    align_put_bits(&s->pb);
103

    
104
    /* Update the pointer to last GOB */
105
    s->ptr_lastgob = pbBufPtr(&s->pb);
106

    
107
    put_bits(&s->pb, 20, 0x10); /* PSC */
108

    
109
    temp_ref= s->picture_number * (int64_t)30000 * s->avctx->time_base.num /
110
                         (1001 * (int64_t)s->avctx->time_base.den); //FIXME maybe this should use a timestamp
111
    put_bits(&s->pb, 5, temp_ref & 0x1f); /* TemporalReference */
112

    
113
    put_bits(&s->pb, 1, 0); /* split screen off */
114
    put_bits(&s->pb, 1, 0); /* camera  off */
115
    put_bits(&s->pb, 1, 0); /* freeze picture release off */
116

    
117
    format = ff_h261_get_picture_format(s->width, s->height);
118

    
119
    put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
120

    
121
    put_bits(&s->pb, 1, 0); /* still image mode */
122
    put_bits(&s->pb, 1, 0); /* reserved */
123

    
124
    put_bits(&s->pb, 1, 0); /* no PEI */
125
    if(format == 0)
126
        h->gob_number = -1;
127
    else
128
        h->gob_number = 0;
129
    h->current_mba = 0;
130
}
131

    
132
/**
133
 * Encodes a group of blocks header.
134
 */
135
static void h261_encode_gob_header(MpegEncContext * s, int mb_line){
136
    H261Context * h = (H261Context *)s;
137
    if(ff_h261_get_picture_format(s->width, s->height) == 0){
138
        h->gob_number+=2; // QCIF
139
    }
140
    else{
141
        h->gob_number++; // CIF
142
    }
143
    put_bits(&s->pb, 16, 1); /* GBSC */
144
    put_bits(&s->pb, 4, h->gob_number); /* GN */
145
    put_bits(&s->pb, 5, s->qscale); /* GQUANT */
146
    put_bits(&s->pb, 1, 0); /* no GEI */
147
    h->current_mba = 0;
148
    h->previous_mba = 0;
149
    h->current_mv_x=0;
150
    h->current_mv_y=0;
151
}
152

    
153
void ff_h261_reorder_mb_index(MpegEncContext* s){
154
    int index= s->mb_x + s->mb_y*s->mb_width;
155

    
156
    if(index % 33 == 0)
157
        h261_encode_gob_header(s,0);
158

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

    
167
        ff_init_block_index(s);
168
        ff_update_block_index(s);
169
    }
170
}
171

    
172
static void h261_encode_motion(H261Context * h, int val){
173
    MpegEncContext * const s = &h->s;
174
    int sign, code;
175
    if(val==0){
176
        code = 0;
177
        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
178
    }
179
    else{
180
        if(val > 15)
181
            val -=32;
182
        if(val < -16)
183
            val+=32;
184
        sign = val < 0;
185
        code = sign ? -val : val;
186
        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
187
        put_bits(&s->pb,1,sign);
188
    }
189
}
190

    
191
static inline int get_cbp(MpegEncContext * s,
192
                      DCTELEM block[6][64])
193
{
194
    int i, cbp;
195
    cbp= 0;
196
    for (i = 0; i < 6; i++) {
197
        if (s->block_last_index[i] >= 0)
198
            cbp |= 1 << (5 - i);
199
    }
200
    return cbp;
201
}
202
void ff_h261_encode_mb(MpegEncContext * s,
203
         DCTELEM block[6][64],
204
         int motion_x, int motion_y)
205
{
206
    H261Context * h = (H261Context *)s;
207
    int mvd, mv_diff_x, mv_diff_y, i, cbp;
208
    cbp = 63; // avoid warning
209
    mvd = 0;
210

    
211
    h->current_mba++;
212
    h->mtype = 0;
213

    
214
    if (!s->mb_intra){
215
        /* compute cbp */
216
        cbp= get_cbp(s, block);
217

    
218
        /* mvd indicates if this block is motion compensated */
219
        mvd = motion_x | motion_y;
220

    
221
        if((cbp | mvd | s->dquant ) == 0) {
222
            /* skip macroblock */
223
            s->skip_count++;
224
            h->current_mv_x=0;
225
            h->current_mv_y=0;
226
            return;
227
        }
228
    }
229

    
230
    /* MB is not skipped, encode MBA */
231
    put_bits(&s->pb, h261_mba_bits[(h->current_mba-h->previous_mba)-1], h261_mba_code[(h->current_mba-h->previous_mba)-1]);
232

    
233
    /* calculate MTYPE */
234
    if(!s->mb_intra){
235
        h->mtype++;
236

    
237
        if(mvd || s->loop_filter)
238
            h->mtype+=3;
239
        if(s->loop_filter)
240
            h->mtype+=3;
241
        if(cbp || s->dquant)
242
            h->mtype++;
243
        assert(h->mtype > 1);
244
    }
245

    
246
    if(s->dquant)
247
        h->mtype++;
248

    
249
    put_bits(&s->pb, h261_mtype_bits[h->mtype], h261_mtype_code[h->mtype]);
250

    
251
    h->mtype = h261_mtype_map[h->mtype];
252

    
253
    if(IS_QUANT(h->mtype)){
254
        ff_set_qscale(s,s->qscale+s->dquant);
255
        put_bits(&s->pb, 5, s->qscale);
256
    }
257

    
258
    if(IS_16X16(h->mtype)){
259
        mv_diff_x = (motion_x >> 1) - h->current_mv_x;
260
        mv_diff_y = (motion_y >> 1) - h->current_mv_y;
261
        h->current_mv_x = (motion_x >> 1);
262
        h->current_mv_y = (motion_y >> 1);
263
        h261_encode_motion(h,mv_diff_x);
264
        h261_encode_motion(h,mv_diff_y);
265
    }
266

    
267
    h->previous_mba = h->current_mba;
268

    
269
    if(HAS_CBP(h->mtype)){
270
        assert(cbp>0);
271
        put_bits(&s->pb,h261_cbp_tab[cbp-1][1],h261_cbp_tab[cbp-1][0]);
272
    }
273
    for(i=0; i<6; i++) {
274
        /* encode each block */
275
        h261_encode_block(h, block[i], i);
276
    }
277

    
278
    if ( ( h->current_mba == 11 ) || ( h->current_mba == 22 ) || ( h->current_mba == 33 ) || ( !IS_16X16 ( h->mtype ) )){
279
        h->current_mv_x=0;
280
        h->current_mv_y=0;
281
    }
282
}
283

    
284
void ff_h261_encode_init(MpegEncContext *s){
285
    static int done = 0;
286

    
287
    if (!done) {
288
        done = 1;
289
        init_rl(&h261_rl_tcoeff, static_rl_table_store);
290
    }
291

    
292
    s->min_qcoeff= -127;
293
    s->max_qcoeff=  127;
294
    s->y_dc_scale_table=
295
    s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
296
}
297

    
298

    
299
/**
300
 * encodes a 8x8 block.
301
 * @param block the 8x8 block
302
 * @param n block index (0-3 are luma, 4-5 are chroma)
303
 */
304
static void h261_encode_block(H261Context * h, DCTELEM * block, int n){
305
    MpegEncContext * const s = &h->s;
306
    int level, run, last, i, j, last_index, last_non_zero, sign, slevel, code;
307
    RLTable *rl;
308

    
309
    rl = &h261_rl_tcoeff;
310
    if (s->mb_intra) {
311
        /* DC coef */
312
        level = block[0];
313
        /* 255 cannot be represented, so we clamp */
314
        if (level > 254) {
315
            level = 254;
316
            block[0] = 254;
317
        }
318
        /* 0 cannot be represented also */
319
        else if (level < 1) {
320
            level = 1;
321
            block[0] = 1;
322
        }
323
        if (level == 128)
324
            put_bits(&s->pb, 8, 0xff);
325
        else
326
            put_bits(&s->pb, 8, level);
327
        i = 1;
328
    } else if((block[0]==1 || block[0] == -1) && (s->block_last_index[n] > -1)){
329
        //special case
330
        put_bits(&s->pb,2,block[0]>0 ? 2 : 3 );
331
        i = 1;
332
    } else {
333
        i = 0;
334
    }
335

    
336
    /* AC coefs */
337
    last_index = s->block_last_index[n];
338
    last_non_zero = i - 1;
339
    for (; i <= last_index; i++) {
340
        j = s->intra_scantable.permutated[i];
341
        level = block[j];
342
        if (level) {
343
            run = i - last_non_zero - 1;
344
            last = (i == last_index);
345
            sign = 0;
346
            slevel = level;
347
            if (level < 0) {
348
                sign = 1;
349
                level = -level;
350
            }
351
            code = get_rl_index(rl, 0 /*no last in H.261, EOB is used*/, run, level);
352
            if(run==0 && level < 16)
353
            code+=1;
354
            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
355
            if (code == rl->n) {
356
                put_bits(&s->pb, 6, run);
357
                assert(slevel != 0);
358
                assert(level <= 127);
359
                put_bits(&s->pb, 8, slevel & 0xff);
360
            } else {
361
                put_bits(&s->pb, 1, sign);
362
            }
363
            last_non_zero = i;
364
        }
365
    }
366
    if(last_index > -1){
367
        put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]);// END OF BLOCK
368
    }
369
}
370

    
371
/***********************************************/
372
/* decoding */
373

    
374
static VLC h261_mba_vlc;
375
static VLC h261_mtype_vlc;
376
static VLC h261_mv_vlc;
377
static VLC h261_cbp_vlc;
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, 1);
387
        init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
388
                 h261_mtype_bits, 1, 1,
389
                 h261_mtype_code, 1, 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, 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, 1);
396
        init_rl(&h261_rl_tcoeff, static_rl_table_store);
397
        init_vlc_rl(&h261_rl_tcoeff, 1);
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

    
537
        for(j=0;j<6;j++)
538
            s->block_last_index[j] = -1;
539

    
540
        s->mv_dir = MV_DIR_FORWARD;
541
        s->mv_type = MV_TYPE_16X16;
542
        s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
543
        s->mv[0][0][0] = 0;
544
        s->mv[0][0][1] = 0;
545
        s->mb_skipped = 1;
546
        h->mtype &= ~MB_TYPE_H261_FIL;
547

    
548
        MPV_decode_mb(s, s->block);
549
    }
550

    
551
    return 0;
552
}
553

    
554
static int decode_mv_component(GetBitContext *gb, int v){
555
    int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
556

    
557
    /* check if mv_diff is valid */
558
    if ( mv_diff < 0 )
559
        return v;
560

    
561
    mv_diff = mvmap[mv_diff];
562

    
563
    if(mv_diff && !get_bits1(gb))
564
        mv_diff= -mv_diff;
565

    
566
    v += mv_diff;
567
    if     (v <=-16) v+= 32;
568
    else if(v >= 16) v-= 32;
569

    
570
    return v;
571
}
572

    
573
static int h261_decode_mb(H261Context *h){
574
    MpegEncContext * const s = &h->s;
575
    int i, cbp, xy;
576

    
577
    cbp = 63;
578
    // Read mba
579
    do{
580
        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
581

    
582
        /* Check for slice end */
583
        /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
584
        if (h->mba_diff == MBA_STARTCODE){ // start code
585
            h->gob_start_code_skipped = 1;
586
            return SLICE_END;
587
        }
588
    }
589
    while( h->mba_diff == MBA_STUFFING ); // stuffing
590

    
591
    if ( h->mba_diff < 0 ){
592
        if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
593
            return SLICE_END;
594

    
595
        av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
596
        return SLICE_ERROR;
597
    }
598

    
599
    h->mba_diff += 1;
600
    h->current_mba += h->mba_diff;
601

    
602
    if ( h->current_mba > MBA_STUFFING )
603
        return SLICE_ERROR;
604

    
605
    s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
606
    s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
607
    xy = s->mb_x + s->mb_y * s->mb_stride;
608
    ff_init_block_index(s);
609
    ff_update_block_index(s);
610

    
611
    // Read mtype
612
    h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
613
    h->mtype = h261_mtype_map[h->mtype];
614

    
615
    // Read mquant
616
    if ( IS_QUANT ( h->mtype ) ){
617
        ff_set_qscale(s, get_bits(&s->gb, 5));
618
    }
619

    
620
    s->mb_intra = IS_INTRA4x4(h->mtype);
621

    
622
    // Read mv
623
    if ( IS_16X16 ( h->mtype ) ){
624
        // Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the
625
        // vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the
626
        // following three situations:
627
        // 1) evaluating MVD for macroblocks 1, 12 and 23;
628
        // 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
629
        // 3) MTYPE of the previous macroblock was not MC.
630
        if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) ||
631
             ( h->mba_diff != 1))
632
        {
633
            h->current_mv_x = 0;
634
            h->current_mv_y = 0;
635
        }
636

    
637
        h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
638
        h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
639
    }else{
640
        h->current_mv_x = 0;
641
        h->current_mv_y = 0;
642
    }
643

    
644
    // Read cbp
645
    if ( HAS_CBP( h->mtype ) ){
646
        cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
647
    }
648

    
649
    if(s->mb_intra){
650
        s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
651
        goto intra;
652
    }
653

    
654
    //set motion vectors
655
    s->mv_dir = MV_DIR_FORWARD;
656
    s->mv_type = MV_TYPE_16X16;
657
    s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
658
    s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation
659
    s->mv[0][0][1] = h->current_mv_y * 2;
660

    
661
intra:
662
    /* decode each block */
663
    if(s->mb_intra || HAS_CBP(h->mtype)){
664
        s->dsp.clear_blocks(s->block[0]);
665
        for (i = 0; i < 6; i++) {
666
            if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
667
                return SLICE_ERROR;
668
            }
669
            cbp+=cbp;
670
        }
671
    }else{
672
        for (i = 0; i < 6; i++)
673
            s->block_last_index[i]= -1;
674
    }
675

    
676
    MPV_decode_mb(s, s->block);
677

    
678
    return SLICE_OK;
679
}
680

    
681
/**
682
 * decodes a macroblock
683
 * @return <0 if an error occured
684
 */
685
static int h261_decode_block(H261Context * h, DCTELEM * block,
686
                             int n, int coded)
687
{
688
    MpegEncContext * const s = &h->s;
689
    int code, level, i, j, run;
690
    RLTable *rl = &h261_rl_tcoeff;
691
    const uint8_t *scan_table;
692

    
693
    // For the variable length encoding there are two code tables, one being used for
694
    // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
695
    // for all other LEVELs except the first one in INTRA blocks which is fixed length
696
    // coded with 8 bits.
697
    // NOTE: the two code tables only differ in one VLC so we handle that manually.
698
    scan_table = s->intra_scantable.permutated;
699
    if (s->mb_intra){
700
        /* DC coef */
701
        level = get_bits(&s->gb, 8);
702
        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
703
        if((level&0x7F) == 0){
704
            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
705
            return -1;
706
        }
707
        // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
708
        if (level == 255)
709
            level = 128;
710
        block[0] = level;
711
        i = 1;
712
    }else if(coded){
713
        // Run  Level   Code
714
        // EOB                  Not possible for first level when cbp is available (that's why the table is different)
715
        // 0    1               1s
716
        // *    *               0*
717
        int check = show_bits(&s->gb, 2);
718
        i = 0;
719
        if ( check & 0x2 ){
720
            skip_bits(&s->gb, 2);
721
            block[0] = ( check & 0x1 ) ? -1 : 1;
722
            i = 1;
723
        }
724
    }else{
725
        i = 0;
726
    }
727
    if(!coded){
728
        s->block_last_index[n] = i - 1;
729
        return 0;
730
    }
731
    for(;;){
732
        code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
733
        if (code < 0){
734
            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
735
            return -1;
736
        }
737
        if (code == rl->n) {
738
            /* escape */
739
            // 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.
740
            run = get_bits(&s->gb, 6);
741
            level = get_sbits(&s->gb, 8);
742
        }else if(code == 0){
743
            break;
744
        }else{
745
            run = rl->table_run[code];
746
            level = rl->table_level[code];
747
            if (get_bits1(&s->gb))
748
                level = -level;
749
        }
750
        i += run;
751
        if (i >= 64){
752
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
753
            return -1;
754
        }
755
        j = scan_table[i];
756
        block[j] = level;
757
        i++;
758
    }
759
    s->block_last_index[n] = i-1;
760
    return 0;
761
}
762

    
763
/**
764
 * decodes the H261 picture header.
765
 * @return <0 if no startcode found
766
 */
767
static int h261_decode_picture_header(H261Context *h){
768
    MpegEncContext * const s = &h->s;
769
    int format, i;
770
    uint32_t startcode= 0;
771

    
772
    for(i= s->gb.size_in_bits - get_bits_count(&s->gb); i>24; i-=1){
773
        startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
774

    
775
        if(startcode == 0x10)
776
            break;
777
    }
778

    
779
    if (startcode != 0x10){
780
        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
781
        return -1;
782
    }
783

    
784
    /* temporal reference */
785
    i= get_bits(&s->gb, 5); /* picture timestamp */
786
    if(i < (s->picture_number&31))
787
        i += 32;
788
    s->picture_number = (s->picture_number&~31) + i;
789

    
790
    s->avctx->time_base= (AVRational){1001, 30000};
791
    s->current_picture.pts= s->picture_number;
792

    
793

    
794
    /* PTYPE starts here */
795
    skip_bits1(&s->gb); /* split screen off */
796
    skip_bits1(&s->gb); /* camera  off */
797
    skip_bits1(&s->gb); /* freeze picture release off */
798

    
799
    format = get_bits1(&s->gb);
800

    
801
    //only 2 formats possible
802
    if (format == 0){//QCIF
803
        s->width = 176;
804
        s->height = 144;
805
        s->mb_width = 11;
806
        s->mb_height = 9;
807
    }else{//CIF
808
        s->width = 352;
809
        s->height = 288;
810
        s->mb_width = 22;
811
        s->mb_height = 18;
812
    }
813

    
814
    s->mb_num = s->mb_width * s->mb_height;
815

    
816
    skip_bits1(&s->gb); /* still image mode off */
817
    skip_bits1(&s->gb); /* Reserved */
818

    
819
    /* PEI */
820
    while (get_bits1(&s->gb) != 0){
821
        skip_bits(&s->gb, 8);
822
    }
823

    
824
    // h261 has no I-FRAMES, but if we pass I_TYPE for the first frame, the codec crashes if it does
825
    // not contain all I-blocks (e.g. when a packet is lost)
826
    s->pict_type = P_TYPE;
827

    
828
    h->gob_number = 0;
829
    return 0;
830
}
831

    
832
static int h261_decode_gob(H261Context *h){
833
    MpegEncContext * const s = &h->s;
834

    
835
    ff_set_qscale(s, s->qscale);
836

    
837
    /* decode mb's */
838
    while(h->current_mba <= MBA_STUFFING)
839
    {
840
        int ret;
841
        /* DCT & quantize */
842
        ret= h261_decode_mb(h);
843
        if(ret<0){
844
            if(ret==SLICE_END){
845
                h261_decode_mb_skipped(h, h->current_mba, 33);
846
                return 0;
847
            }
848
            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
849
            return -1;
850
        }
851

    
852
        h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
853
    }
854

    
855
    return -1;
856
}
857

    
858
/**
859
 * returns the number of bytes consumed for building the current frame
860
 */
861
static int get_consumed_bytes(MpegEncContext *s, int buf_size){
862
    int pos= get_bits_count(&s->gb)>>3;
863
    if(pos==0) pos=1; //avoid infinite loops (i doubt thats needed but ...)
864
    if(pos+10>buf_size) pos=buf_size; // oops ;)
865

    
866
    return pos;
867
}
868

    
869
static int h261_decode_frame(AVCodecContext *avctx,
870
                             void *data, int *data_size,
871
                             uint8_t *buf, int buf_size)
872
{
873
    H261Context *h= avctx->priv_data;
874
    MpegEncContext *s = &h->s;
875
    int ret;
876
    AVFrame *pict = data;
877

    
878
#ifdef DEBUG
879
    av_log(avctx, AV_LOG_DEBUG, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
880
    av_log(avctx, AV_LOG_DEBUG, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
881
#endif
882
    s->flags= avctx->flags;
883
    s->flags2= avctx->flags2;
884

    
885
    h->gob_start_code_skipped=0;
886

    
887
retry:
888

    
889
    init_get_bits(&s->gb, buf, buf_size*8);
890

    
891
    if(!s->context_initialized){
892
        if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
893
            return -1;
894
    }
895

    
896
    //we need to set current_picture_ptr before reading the header, otherwise we cant store anyting im there
897
    if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
898
        int i= ff_find_unused_picture(s, 0);
899
        s->current_picture_ptr= &s->picture[i];
900
    }
901

    
902
    ret = h261_decode_picture_header(h);
903

    
904
    /* skip if the header was thrashed */
905
    if (ret < 0){
906
        av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
907
        return -1;
908
    }
909

    
910
    if (s->width != avctx->coded_width || s->height != avctx->coded_height){
911
        ParseContext pc= s->parse_context; //FIXME move these demuxng hack to avformat
912
        s->parse_context.buffer=0;
913
        MPV_common_end(s);
914
        s->parse_context= pc;
915
    }
916
    if (!s->context_initialized) {
917
        avcodec_set_dimensions(avctx, s->width, s->height);
918

    
919
        goto retry;
920
    }
921

    
922
    // for hurry_up==5
923
    s->current_picture.pict_type= s->pict_type;
924
    s->current_picture.key_frame= s->pict_type == I_TYPE;
925

    
926
    /* skip everything if we are in a hurry>=5 */
927
    if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
928
    if(  (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==B_TYPE)
929
       ||(avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=I_TYPE)
930
       || avctx->skip_frame >= AVDISCARD_ALL)
931
        return get_consumed_bytes(s, buf_size);
932

    
933
    if(MPV_frame_start(s, avctx) < 0)
934
        return -1;
935

    
936
    ff_er_frame_start(s);
937

    
938
    /* decode each macroblock */
939
    s->mb_x=0;
940
    s->mb_y=0;
941

    
942
    while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
943
        if(ff_h261_resync(h)<0)
944
            break;
945
        h261_decode_gob(h);
946
    }
947
    MPV_frame_end(s);
948

    
949
assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
950
assert(s->current_picture.pict_type == s->pict_type);
951
    *pict= *(AVFrame*)s->current_picture_ptr;
952
    ff_print_debug_info(s, pict);
953

    
954
    *data_size = sizeof(AVFrame);
955

    
956
    return get_consumed_bytes(s, buf_size);
957
}
958

    
959
static int h261_decode_end(AVCodecContext *avctx)
960
{
961
    H261Context *h= avctx->priv_data;
962
    MpegEncContext *s = &h->s;
963

    
964
    MPV_common_end(s);
965
    return 0;
966
}
967

    
968
#ifdef CONFIG_ENCODERS
969
AVCodec h261_encoder = {
970
    "h261",
971
    CODEC_TYPE_VIDEO,
972
    CODEC_ID_H261,
973
    sizeof(H261Context),
974
    MPV_encode_init,
975
    MPV_encode_picture,
976
    MPV_encode_end,
977
    .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, -1},
978
};
979
#endif
980

    
981
AVCodec h261_decoder = {
982
    "h261",
983
    CODEC_TYPE_VIDEO,
984
    CODEC_ID_H261,
985
    sizeof(H261Context),
986
    h261_decode_init,
987
    NULL,
988
    h261_decode_end,
989
    h261_decode_frame,
990
    CODEC_CAP_DR1,
991
};