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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 gob_start_code_skipped; // 1 if gob start code is already read before gob header is read
57
}H261Context;
58

    
59
void ff_h261_loop_filter(MpegEncContext *s){
60
    H261Context * h= (H261Context*)s;
61
    const int linesize  = s->linesize;
62
    const int uvlinesize= s->uvlinesize;
63
    uint8_t *dest_y = s->dest[0];
64
    uint8_t *dest_cb= s->dest[1];
65
    uint8_t *dest_cr= s->dest[2];
66

    
67
    if(!(IS_FIL (h->mtype)))
68
        return;
69

    
70
    s->dsp.h261_loop_filter(dest_y                   , linesize);
71
    s->dsp.h261_loop_filter(dest_y                + 8, linesize);
72
    s->dsp.h261_loop_filter(dest_y + 8 * linesize    , linesize);
73
    s->dsp.h261_loop_filter(dest_y + 8 * linesize + 8, linesize);
74
    s->dsp.h261_loop_filter(dest_cb, uvlinesize);
75
    s->dsp.h261_loop_filter(dest_cr, uvlinesize);
76
}
77

    
78
static int ff_h261_get_picture_format(int width, int height){
79
    // QCIF
80
    if (width == 176 && height == 144)
81
        return 0;
82
    // CIF
83
    else if (width == 352 && height == 288)
84
        return 1;
85
    // ERROR
86
    else
87
        return -1;
88
}
89

    
90
static void h261_encode_block(H261Context * h, DCTELEM * block,
91
                              int n);
92
static int h261_decode_block(H261Context *h, DCTELEM *block,
93
                             int n, int coded);
94

    
95
void ff_h261_encode_picture_header(MpegEncContext * s, int picture_number){
96
    H261Context * h = (H261Context *) s;
97
    int format, temp_ref;
98

    
99
    align_put_bits(&s->pb);
100

    
101
    /* Update the pointer to last GOB */
102
    s->ptr_lastgob = pbBufPtr(&s->pb);
103

    
104
    put_bits(&s->pb, 20, 0x10); /* PSC */
105

    
106
    temp_ref= s->picture_number * (int64_t)30000 * s->avctx->frame_rate_base / 
107
                         (1001 * (int64_t)s->avctx->frame_rate);
108
    put_bits(&s->pb, 5, temp_ref & 0x1f); /* TemporalReference */
109

    
110
    put_bits(&s->pb, 1, 0); /* split screen off */
111
    put_bits(&s->pb, 1, 0); /* camera  off */
112
    put_bits(&s->pb, 1, 0); /* freeze picture release off */
113
    
114
    format = ff_h261_get_picture_format(s->width, s->height);
115
    
116
    put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
117

    
118
    put_bits(&s->pb, 1, 0); /* still image mode */
119
    put_bits(&s->pb, 1, 0); /* reserved */
120

    
121
    put_bits(&s->pb, 1, 0); /* no PEI */    
122
    if(format == 0)
123
        h->gob_number = -1;
124
    else
125
        h->gob_number = 0;
126
    h->current_mba = 0;
127
}
128

    
129
/**
130
 * Encodes a group of blocks header.
131
 */
132
static void h261_encode_gob_header(MpegEncContext * s, int mb_line){
133
    H261Context * h = (H261Context *)s;
134
    if(ff_h261_get_picture_format(s->width, s->height) == 0){
135
        h->gob_number+=2; // QCIF
136
    }
137
    else{
138
        h->gob_number++; // CIF
139
    }
140
    put_bits(&s->pb, 16, 1); /* GBSC */
141
    put_bits(&s->pb, 4, h->gob_number); /* GN */
142
    put_bits(&s->pb, 5, s->qscale); /* GQUANT */
143
    put_bits(&s->pb, 1, 0); /* no GEI */
144
    h->current_mba = 0;
145
    h->previous_mba = 0;
146
    h->current_mv_x=0;
147
    h->current_mv_y=0;
148
}
149

    
150
void ff_h261_reorder_mb_index(MpegEncContext* s){
151
    int index= s->mb_x + s->mb_y*s->mb_width;
152

    
153
    if(index % 33 == 0)
154
        h261_encode_gob_header(s,0);
155

    
156
    /* for CIF the GOB's are fragmented in the middle of a scanline
157
       that's why we need to adjust the x and y index of the macroblocks */
158
    if(ff_h261_get_picture_format(s->width,s->height) == 1){ // CIF
159
        s->mb_x =     index % 11 ; index /= 11;
160
        s->mb_y =     index %  3 ; index /=  3;
161
        s->mb_x+= 11*(index %  2); index /=  2;
162
        s->mb_y+=  3*index;
163
        
164
        ff_init_block_index(s);
165
        ff_update_block_index(s);
166
    }
167
}
168

    
169
static void h261_encode_motion(H261Context * h, int val){
170
    MpegEncContext * const s = &h->s;
171
    int sign, code;
172
    if(val==0){
173
        code = 0;
174
        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
175
    } 
176
    else{
177
        if(val > 15)
178
            val -=32;
179
        if(val < -16)
180
            val+=32;
181
        sign = val < 0;
182
        code = sign ? -val : val; 
183
        put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
184
        put_bits(&s->pb,1,sign);
185
    }
186
}
187

    
188
static inline int get_cbp(MpegEncContext * s,
189
                      DCTELEM block[6][64])
190
{
191
    int i, cbp;
192
    cbp= 0;
193
    for (i = 0; i < 6; i++) {
194
        if (s->block_last_index[i] >= 0)
195
            cbp |= 1 << (5 - i);
196
    }
197
    return cbp;
198
}
199
void ff_h261_encode_mb(MpegEncContext * s,
200
         DCTELEM block[6][64],
201
         int motion_x, int motion_y)
202
{
203
    H261Context * h = (H261Context *)s;
204
    int mvd, mv_diff_x, mv_diff_y, i, cbp;
205
    cbp = 63; // avoid warning
206
    mvd = 0;
207
 
208
    h->current_mba++;
209
    h->mtype = 0;
210
 
211
    if (!s->mb_intra){
212
        /* compute cbp */
213
        cbp= get_cbp(s, block);
214
   
215
        /* mvd indicates if this block is motion compensated */
216
        mvd = motion_x | motion_y;
217

    
218
        if((cbp | mvd | s->dquant ) == 0) {
219
            /* skip macroblock */
220
            s->skip_count++;
221
            h->current_mv_x=0;
222
            h->current_mv_y=0;
223
            return;
224
        }
225
    }
226

    
227
    /* MB is not skipped, encode MBA */
228
    put_bits(&s->pb, h261_mba_bits[(h->current_mba-h->previous_mba)-1], h261_mba_code[(h->current_mba-h->previous_mba)-1]);
229
 
230
    /* calculate MTYPE */
231
    if(!s->mb_intra){
232
        h->mtype++;
233
        
234
        if(mvd || s->loop_filter)
235
            h->mtype+=3;
236
        if(s->loop_filter)
237
            h->mtype+=3;
238
        if(cbp || s->dquant)
239
            h->mtype++;
240
        assert(h->mtype > 1);
241
    }
242

    
243
    if(s->dquant) 
244
        h->mtype++;
245

    
246
    put_bits(&s->pb, h261_mtype_bits[h->mtype], h261_mtype_code[h->mtype]);
247
 
248
    h->mtype = h261_mtype_map[h->mtype];
249
 
250
    if(IS_QUANT(h->mtype)){
251
        ff_set_qscale(s,s->qscale+s->dquant);
252
        put_bits(&s->pb, 5, s->qscale);
253
    }
254
 
255
    if(IS_16X16(h->mtype)){
256
        mv_diff_x = (motion_x >> 1) - h->current_mv_x;
257
        mv_diff_y = (motion_y >> 1) - h->current_mv_y;
258
        h->current_mv_x = (motion_x >> 1);
259
        h->current_mv_y = (motion_y >> 1);
260
        h261_encode_motion(h,mv_diff_x);
261
        h261_encode_motion(h,mv_diff_y);
262
    }
263
 
264
    h->previous_mba = h->current_mba;
265
 
266
    if(HAS_CBP(h->mtype)){
267
        put_bits(&s->pb,h261_cbp_tab[cbp-1][1],h261_cbp_tab[cbp-1][0]); 
268
    }
269
    for(i=0; i<6; i++) {
270
        /* encode each block */
271
        h261_encode_block(h, block[i], i);
272
    }
273

    
274
    if ( ( h->current_mba == 11 ) || ( h->current_mba == 22 ) || ( h->current_mba == 33 ) || ( !IS_16X16 ( h->mtype ) )){
275
        h->current_mv_x=0;
276
        h->current_mv_y=0;
277
    }
278
}
279

    
280
void ff_h261_encode_init(MpegEncContext *s){
281
    static int done = 0;
282
    
283
    if (!done) {
284
        done = 1;
285
        init_rl(&h261_rl_tcoeff, 1);
286
    }
287

    
288
    s->min_qcoeff= -127;
289
    s->max_qcoeff=  127;
290
    s->y_dc_scale_table=
291
    s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
292
}
293

    
294

    
295
/**
296
 * encodes a 8x8 block.
297
 * @param block the 8x8 block
298
 * @param n block index (0-3 are luma, 4-5 are chroma)
299
 */
300
static void h261_encode_block(H261Context * h, DCTELEM * block, int n){
301
    MpegEncContext * const s = &h->s;
302
    int level, run, last, i, j, last_index, last_non_zero, sign, slevel, code;
303
    RLTable *rl;
304

    
305
    rl = &h261_rl_tcoeff;
306
    if (s->mb_intra) {
307
        /* DC coef */
308
        level = block[0];
309
        /* 255 cannot be represented, so we clamp */
310
        if (level > 254) {
311
            level = 254;
312
            block[0] = 254;
313
        }
314
        /* 0 cannot be represented also */
315
        else if (level < 1) {
316
            level = 1;
317
            block[0] = 1;
318
        }
319
        if (level == 128)
320
            put_bits(&s->pb, 8, 0xff);
321
        else
322
            put_bits(&s->pb, 8, level);
323
        i = 1;
324
    } else if((block[0]==1 || block[0] == -1) && (s->block_last_index[n] > -1)){
325
        //special case
326
        put_bits(&s->pb,2,block[0]>0 ? 2 : 3 );
327
        i = 1;
328
    } else {
329
        i = 0;
330
    }
331
   
332
    /* AC coefs */
333
    last_index = s->block_last_index[n];
334
    last_non_zero = i - 1;
335
    for (; i <= last_index; i++) {
336
        j = s->intra_scantable.permutated[i];
337
        level = block[j];
338
        if (level) {
339
            run = i - last_non_zero - 1;
340
            last = (i == last_index);
341
            sign = 0;
342
            slevel = level;
343
            if (level < 0) {
344
                sign = 1;
345
                level = -level;
346
            }
347
            code = get_rl_index(rl, 0 /*no last in H.261, EOB is used*/, run, level);
348
            if(run==0 && level < 16)
349
            code+=1;
350
            put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
351
            if (code == rl->n) {
352
                put_bits(&s->pb, 6, run);
353
                assert(slevel != 0);
354
                assert(level <= 127);
355
                put_bits(&s->pb, 8, slevel & 0xff);
356
            } else {
357
                put_bits(&s->pb, 1, sign);
358
            }
359
            last_non_zero = i;
360
        }
361
    }
362
    if(last_index > -1){
363
        put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]);// END OF BLOCK
364
    }
365
}
366

    
367
/***********************************************/
368
/* decoding */
369

    
370
static VLC h261_mba_vlc;
371
static VLC h261_mtype_vlc;
372
static VLC h261_mv_vlc;
373
static VLC h261_cbp_vlc;
374

    
375
void init_vlc_rl(RLTable *rl, int use_static);
376

    
377
static void h261_decode_init_vlc(H261Context *h){
378
    static int done = 0;
379

    
380
    if(!done){
381
        done = 1;
382
        init_vlc(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
383
                 h261_mba_bits, 1, 1,
384
                 h261_mba_code, 1, 1, 1);
385
        init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
386
                 h261_mtype_bits, 1, 1,
387
                 h261_mtype_code, 1, 1, 1);
388
        init_vlc(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
389
                 &h261_mv_tab[0][1], 2, 1,
390
                 &h261_mv_tab[0][0], 2, 1, 1);
391
        init_vlc(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
392
                 &h261_cbp_tab[0][1], 2, 1,
393
                 &h261_cbp_tab[0][0], 2, 1, 1);
394
        init_rl(&h261_rl_tcoeff, 1);
395
        init_vlc_rl(&h261_rl_tcoeff, 1);
396
    }
397
}
398

    
399
static int h261_decode_init(AVCodecContext *avctx){
400
    H261Context *h= avctx->priv_data;
401
    MpegEncContext * const s = &h->s;
402

    
403
    // set defaults
404
    MPV_decode_defaults(s);
405
    s->avctx = avctx;
406

    
407
    s->width  = s->avctx->coded_width;
408
    s->height = s->avctx->coded_height;
409
    s->codec_id = s->avctx->codec->id;
410

    
411
    s->out_format = FMT_H261;
412
    s->low_delay= 1;
413
    avctx->pix_fmt= PIX_FMT_YUV420P;
414

    
415
    s->codec_id= avctx->codec->id;
416

    
417
    h261_decode_init_vlc(h);
418

    
419
    h->gob_start_code_skipped = 0;
420
    
421
    return 0;
422
}
423

    
424
/**
425
 * decodes the group of blocks header or slice header.
426
 * @return <0 if an error occured
427
 */
428
static int h261_decode_gob_header(H261Context *h){
429
    unsigned int val;
430
    MpegEncContext * const s = &h->s;
431
    
432
    if ( !h->gob_start_code_skipped ){
433
        /* Check for GOB Start Code */
434
        val = show_bits(&s->gb, 15);
435
        if(val)
436
            return -1;
437

    
438
        /* We have a GBSC */
439
        skip_bits(&s->gb, 16);
440
    }
441

    
442
    h->gob_start_code_skipped = 0;
443

    
444
    h->gob_number = get_bits(&s->gb, 4); /* GN */
445
    s->qscale = get_bits(&s->gb, 5); /* GQUANT */
446

    
447
    /* Check if gob_number is valid */
448
    if (s->mb_height==18){ //cif
449
        if ((h->gob_number<=0) || (h->gob_number>12))
450
            return -1;
451
    }
452
    else{ //qcif
453
        if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
454
            return -1;
455
    }
456

    
457
    /* GEI */
458
    while (get_bits1(&s->gb) != 0) {
459
        skip_bits(&s->gb, 8);
460
    }
461

    
462
    if(s->qscale==0)
463
        return -1;
464

    
465
    // For the first transmitted macroblock in a GOB, MBA is the absolute address. For
466
    // subsequent macroblocks, MBA is the difference between the absolute addresses of
467
    // the macroblock and the last transmitted macroblock.
468
    h->current_mba = 0;
469
    h->mba_diff = 0;
470

    
471
    return 0;
472
}
473

    
474
/**
475
 * decodes the group of blocks / video packet header.
476
 * @return <0 if no resync found
477
 */
478
static int ff_h261_resync(H261Context *h){
479
    MpegEncContext * const s = &h->s;
480
    int left, ret;
481

    
482
    if ( h->gob_start_code_skipped ){
483
        ret= h261_decode_gob_header(h);
484
        if(ret>=0)
485
            return 0;
486
    }
487
    else{
488
        if(show_bits(&s->gb, 15)==0){
489
            ret= h261_decode_gob_header(h);
490
            if(ret>=0)
491
                return 0;
492
        }
493
        //ok, its not where its supposed to be ...
494
        s->gb= s->last_resync_gb;
495
        align_get_bits(&s->gb);
496
        left= s->gb.size_in_bits - get_bits_count(&s->gb);
497

    
498
        for(;left>15+1+4+5; left-=8){
499
            if(show_bits(&s->gb, 15)==0){
500
                GetBitContext bak= s->gb;
501

    
502
                ret= h261_decode_gob_header(h);
503
                if(ret>=0)
504
                    return 0;
505

    
506
                s->gb= bak;
507
            }
508
            skip_bits(&s->gb, 8);
509
        }
510
    }
511

    
512
    return -1;
513
}
514

    
515
/**
516
 * decodes skipped macroblocks
517
 * @return 0
518
 */
519
static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
520
{
521
    MpegEncContext * const s = &h->s;
522
    int i;
523
    
524
    s->mb_intra = 0;
525

    
526
    for(i=mba1; i<mba2; i++){
527
        int j, xy;
528

    
529
        s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
530
        s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
531
        xy = s->mb_x + s->mb_y * s->mb_stride;
532
        ff_init_block_index(s);
533
        ff_update_block_index(s);
534
        s->dsp.clear_blocks(s->block[0]);
535

    
536
        for(j=0;j<6;j++)
537
            s->block_last_index[j] = -1;
538

    
539
        s->mv_dir = MV_DIR_FORWARD;
540
        s->mv_type = MV_TYPE_16X16;
541
        s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
542
        s->mv[0][0][0] = 0;
543
        s->mv[0][0][1] = 0;
544
        s->mb_skiped = 1;
545
        h->mtype &= ~MB_TYPE_H261_FIL;
546

    
547
        MPV_decode_mb(s, s->block);
548
    }
549

    
550
    return 0;
551
}
552

    
553
static int decode_mv_component(GetBitContext *gb, int v){
554
    int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
555

    
556
    /* check if mv_diff is valid */
557
    if ( mv_diff < 0 )
558
        return v;
559

    
560
    mv_diff = mvmap[mv_diff];
561

    
562
    if(mv_diff && !get_bits1(gb))
563
        mv_diff= -mv_diff;
564
    
565
    v += mv_diff;
566
    if     (v <=-16) v+= 32;
567
    else if(v >= 16) v-= 32;
568

    
569
    return v;
570
}
571

    
572
static int h261_decode_mb(H261Context *h){
573
    MpegEncContext * const s = &h->s;
574
    int i, cbp, xy;
575

    
576
    cbp = 63;
577
    // Read mba
578
    do{
579
        h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
580

    
581
        /* Check for slice end */
582
        /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
583
        if (h->mba_diff == MBA_STARTCODE){ // start code
584
            h->gob_start_code_skipped = 1;
585
            return SLICE_END;
586
        }
587
    }
588
    while( h->mba_diff == MBA_STUFFING ); // stuffing
589

    
590
    if ( h->mba_diff < 0 ){
591
        if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
592
            return SLICE_END;
593

    
594
        av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
595
        return SLICE_ERROR;
596
    }
597

    
598
    h->mba_diff += 1;
599
    h->current_mba += h->mba_diff;
600

    
601
    if ( h->current_mba > MBA_STUFFING )
602
        return SLICE_ERROR;
603
    
604
    s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
605
    s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
606
    xy = s->mb_x + s->mb_y * s->mb_stride;
607
    ff_init_block_index(s);
608
    ff_update_block_index(s);
609
    s->dsp.clear_blocks(s->block[0]);
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
        for (i = 0; i < 6; i++) {
665
            if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
666
                return SLICE_ERROR;
667
            }
668
            cbp+=cbp;
669
        }
670
    }
671

    
672
    MPV_decode_mb(s, s->block);
673

    
674
    return SLICE_OK;
675
}
676

    
677
/**
678
 * decodes a macroblock
679
 * @return <0 if an error occured
680
 */
681
static int h261_decode_block(H261Context * h, DCTELEM * block,
682
                             int n, int coded)
683
{
684
    MpegEncContext * const s = &h->s;
685
    int code, level, i, j, run;
686
    RLTable *rl = &h261_rl_tcoeff;
687
    const uint8_t *scan_table;
688
    
689
    // For the variable length encoding there are two code tables, one being used for
690
    // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
691
    // for all other LEVELs except the first one in INTRA blocks which is fixed length
692
    // coded with 8 bits.
693
    // NOTE: the two code tables only differ in one VLC so we handle that manually.
694
    scan_table = s->intra_scantable.permutated;
695
    if (s->mb_intra){
696
        /* DC coef */
697
        level = get_bits(&s->gb, 8);
698
        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
699
        if((level&0x7F) == 0){
700
            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
701
            return -1;
702
        }
703
        // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
704
        if (level == 255)
705
            level = 128;
706
        block[0] = level;
707
        i = 1;
708
    }else if(coded){
709
        // Run  Level   Code
710
        // EOB                  Not possible for first level when cbp is available (that's why the table is different)
711
        // 0    1               1s
712
        // *    *               0*
713
        int check = show_bits(&s->gb, 2);
714
        i = 0;
715
        if ( check & 0x2 ){
716
            skip_bits(&s->gb, 2);
717
            block[0] = ( check & 0x1 ) ? -1 : 1;
718
            i = 1;
719
        }
720
    }else{
721
        i = 0;
722
    }
723
    if(!coded){
724
        s->block_last_index[n] = i - 1;
725
        return 0;
726
    }
727
    for(;;){
728
        code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
729
        if (code < 0){
730
            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
731
            return -1;
732
        }
733
        if (code == rl->n) {
734
            /* escape */
735
            // 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.
736
            run = get_bits(&s->gb, 6);
737
            level = get_sbits(&s->gb, 8);
738
        }else if(code == 0){
739
            break;
740
        }else{
741
            run = rl->table_run[code];
742
            level = rl->table_level[code];
743
            if (get_bits1(&s->gb))
744
                level = -level;
745
        }
746
        i += run;
747
        if (i >= 64){
748
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
749
            return -1;
750
        }
751
        j = scan_table[i];
752
        block[j] = level;
753
        i++;
754
    }
755
    s->block_last_index[n] = i-1;
756
    return 0;
757
}
758

    
759
/**
760
 * decodes the H261 picture header.
761
 * @return <0 if no startcode found
762
 */
763
int h261_decode_picture_header(H261Context *h){
764
    MpegEncContext * const s = &h->s;
765
    int format, i;
766
    uint32_t startcode= 0;
767

    
768
    for(i= s->gb.size_in_bits - get_bits_count(&s->gb); i>24; i-=1){
769
        startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
770

    
771
        if(startcode == 0x10)
772
            break;
773
    }
774

    
775
    if (startcode != 0x10){
776
        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
777
        return -1;
778
    }
779

    
780
    /* temporal reference */
781
    s->picture_number = get_bits(&s->gb, 5); /* picture timestamp */
782

    
783
    /* PTYPE starts here */
784
    skip_bits1(&s->gb); /* split screen off */
785
    skip_bits1(&s->gb); /* camera  off */
786
    skip_bits1(&s->gb); /* freeze picture release off */
787

    
788
    format = get_bits1(&s->gb);
789

    
790
    //only 2 formats possible
791
    if (format == 0){//QCIF
792
        s->width = 176;
793
        s->height = 144;
794
        s->mb_width = 11;
795
        s->mb_height = 9;
796
    }else{//CIF
797
        s->width = 352;
798
        s->height = 288;
799
        s->mb_width = 22;
800
        s->mb_height = 18;
801
    }
802

    
803
    s->mb_num = s->mb_width * s->mb_height;
804

    
805
    skip_bits1(&s->gb); /* still image mode off */
806
    skip_bits1(&s->gb); /* Reserved */
807

    
808
    /* PEI */
809
    while (get_bits1(&s->gb) != 0){
810
        skip_bits(&s->gb, 8);
811
    }
812

    
813
    // h261 has no I-FRAMES, but if we pass I_TYPE for the first frame, the codec crashes if it does 
814
    // not contain all I-blocks (e.g. when a packet is lost)
815
    s->pict_type = P_TYPE;
816

    
817
    h->gob_number = 0;
818
    return 0;
819
}
820

    
821
static int h261_decode_gob(H261Context *h){
822
    MpegEncContext * const s = &h->s;
823
    
824
    ff_set_qscale(s, s->qscale);
825

    
826
    /* decode mb's */
827
    while(h->current_mba <= MBA_STUFFING)
828
    {
829
        int ret;
830
        /* DCT & quantize */
831
        ret= h261_decode_mb(h);
832
        if(ret<0){
833
            if(ret==SLICE_END){
834
                h261_decode_mb_skipped(h, h->current_mba, 33);                
835
                return 0;
836
            }
837
            av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
838
            return -1;
839
        }
840
        
841
        h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
842
    }
843
    
844
    return -1;
845
}
846

    
847
static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
848
    int vop_found, i, j;
849
    uint32_t state;
850

    
851
    vop_found= pc->frame_start_found;
852
    state= pc->state;
853
   
854
    for(i=0; i<buf_size && !vop_found; i++){
855
        state= (state<<8) | buf[i];
856
        for(j=0; j<8; j++){
857
            if(((state>>j)&0xFFFFF) == 0x00010){
858
                i++;
859
                vop_found=1;
860
                break;
861
            }
862
        }
863
    }
864
    if(vop_found){
865
        for(; i<buf_size; i++){
866
            state= (state<<8) | buf[i];
867
            for(j=0; j<8; j++){
868
                if(((state>>j)&0xFFFFF) == 0x00010){
869
                    pc->frame_start_found=0;
870
                    pc->state= state>>(2*8);
871
                    return i-1;
872
                }
873
            }
874
        }
875
    }
876

    
877
    pc->frame_start_found= vop_found;
878
    pc->state= state;
879
    return END_NOT_FOUND;
880
}
881

    
882
static int h261_parse(AVCodecParserContext *s,
883
                      AVCodecContext *avctx,
884
                      uint8_t **poutbuf, int *poutbuf_size, 
885
                      const uint8_t *buf, int buf_size)
886
{
887
    ParseContext *pc = s->priv_data;
888
    int next;
889
    
890
    next= h261_find_frame_end(pc,avctx, buf, buf_size);
891
    if (ff_combine_frame(pc, next, (uint8_t **)&buf, &buf_size) < 0) {
892
        *poutbuf = NULL;
893
        *poutbuf_size = 0;
894
        return buf_size;
895
    }
896
    *poutbuf = (uint8_t *)buf;
897
    *poutbuf_size = buf_size;
898
    return next;
899
}
900

    
901
/**
902
 * returns the number of bytes consumed for building the current frame
903
 */
904
static int get_consumed_bytes(MpegEncContext *s, int buf_size){
905
    int pos= get_bits_count(&s->gb)>>3;
906
    if(pos==0) pos=1; //avoid infinite loops (i doubt thats needed but ...)
907
    if(pos+10>buf_size) pos=buf_size; // oops ;)
908

    
909
    return pos;
910
}
911

    
912
static int h261_decode_frame(AVCodecContext *avctx,
913
                             void *data, int *data_size,
914
                             uint8_t *buf, int buf_size)
915
{
916
    H261Context *h= avctx->priv_data;
917
    MpegEncContext *s = &h->s;
918
    int ret;
919
    AVFrame *pict = data;
920

    
921
#ifdef DEBUG
922
    printf("*****frame %d size=%d\n", avctx->frame_number, buf_size);
923
    printf("bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
924
#endif
925
    s->flags= avctx->flags;
926
    s->flags2= avctx->flags2;
927

    
928
    /* no supplementary picture */
929
    if (buf_size == 0) {
930
        return 0;
931
    }
932
    
933
    h->gob_start_code_skipped=0;
934

    
935
retry:
936

    
937
    init_get_bits(&s->gb, buf, buf_size*8);
938

    
939
    if(!s->context_initialized){
940
        if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
941
            return -1;
942
    }
943

    
944
    //we need to set current_picture_ptr before reading the header, otherwise we cant store anyting im there
945
    if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
946
        int i= ff_find_unused_picture(s, 0);
947
        s->current_picture_ptr= &s->picture[i];
948
    }
949

    
950
    ret = h261_decode_picture_header(h);
951

    
952
    /* skip if the header was thrashed */
953
    if (ret < 0){
954
        av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
955
        return -1;
956
    }
957

    
958
    if (s->width != avctx->coded_width || s->height != avctx->coded_height){
959
        ParseContext pc= s->parse_context; //FIXME move these demuxng hack to avformat
960
        s->parse_context.buffer=0;
961
        MPV_common_end(s);
962
        s->parse_context= pc;
963
    }
964
    if (!s->context_initialized) {
965
        avcodec_set_dimensions(avctx, s->width, s->height);
966

    
967
        goto retry;
968
    }
969

    
970
    // for hurry_up==5
971
    s->current_picture.pict_type= s->pict_type;
972
    s->current_picture.key_frame= s->pict_type == I_TYPE;
973

    
974
    /* skip everything if we are in a hurry>=5 */
975
    if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
976

    
977
    if(MPV_frame_start(s, avctx) < 0)
978
        return -1;
979

    
980
    ff_er_frame_start(s);
981

    
982
    /* decode each macroblock */
983
    s->mb_x=0;
984
    s->mb_y=0;
985

    
986
    while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
987
        if(ff_h261_resync(h)<0)
988
            break;
989
        h261_decode_gob(h);
990
    }
991
    MPV_frame_end(s);
992

    
993
assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
994
assert(s->current_picture.pict_type == s->pict_type);
995
    *pict= *(AVFrame*)s->current_picture_ptr;
996
    ff_print_debug_info(s, pict);
997

    
998
    /* Return the Picture timestamp as the frame number */
999
    /* we substract 1 because it is added on utils.c    */
1000
    avctx->frame_number = s->picture_number - 1;
1001

    
1002
    *data_size = sizeof(AVFrame);
1003

    
1004
    return get_consumed_bytes(s, buf_size);
1005
}
1006

    
1007
static int h261_decode_end(AVCodecContext *avctx)
1008
{
1009
    H261Context *h= avctx->priv_data;
1010
    MpegEncContext *s = &h->s;
1011

    
1012
    MPV_common_end(s);
1013
    return 0;
1014
}
1015

    
1016
#ifdef CONFIG_ENCODERS
1017
AVCodec h261_encoder = {
1018
    "h261",
1019
    CODEC_TYPE_VIDEO,
1020
    CODEC_ID_H261,
1021
    sizeof(H261Context),
1022
    MPV_encode_init,
1023
    MPV_encode_picture,
1024
    MPV_encode_end,
1025
};
1026
#endif
1027

    
1028
AVCodec h261_decoder = {
1029
    "h261",
1030
    CODEC_TYPE_VIDEO,
1031
    CODEC_ID_H261,
1032
    sizeof(H261Context),
1033
    h261_decode_init,
1034
    NULL,
1035
    h261_decode_end,
1036
    h261_decode_frame,
1037
    CODEC_CAP_DR1,
1038
};
1039

    
1040
AVCodecParser h261_parser = {
1041
    { CODEC_ID_H261 },
1042
    sizeof(ParseContext),
1043
    NULL,
1044
    h261_parse,
1045
    ff_parse_close,
1046
};