summaryrefslogtreecommitdiff
path: root/libavcodec/ituh263dec.c
blob: 148bb33a36cd2d8f05f21af92d6c190da1c9ab9e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
/*
 * ITU H263 bitstream decoder
 * Copyright (c) 2000,2001 Fabrice Bellard
 * H263+ support.
 * Copyright (c) 2001 Juan J. Sierralta P
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * h263 decoder.
 */

//#define DEBUG
#include <limits.h>

#include "libavutil/mathematics.h"
#include "dsputil.h"
#include "avcodec.h"
#include "mpegvideo.h"
#include "h263.h"
#include "mathops.h"
#include "unary.h"
#include "flv.h"
#include "mpeg4video.h"

//#undef NDEBUG
//#include <assert.h>

// The defines below define the number of bits that are read at once for
// reading vlc values. Changing these may improve speed and data cache needs
// be aware though that decreasing them may need the number of stages that is
// passed to get_vlc* to be increased.
#define MV_VLC_BITS 9
#define H263_MBTYPE_B_VLC_BITS 6
#define CBPC_B_VLC_BITS 3

static const int h263_mb_type_b_map[15]= {
    MB_TYPE_DIRECT2 | MB_TYPE_L0L1,
    MB_TYPE_DIRECT2 | MB_TYPE_L0L1 | MB_TYPE_CBP,
    MB_TYPE_DIRECT2 | MB_TYPE_L0L1 | MB_TYPE_CBP | MB_TYPE_QUANT,
                      MB_TYPE_L0                                 | MB_TYPE_16x16,
                      MB_TYPE_L0   | MB_TYPE_CBP                 | MB_TYPE_16x16,
                      MB_TYPE_L0   | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
                      MB_TYPE_L1                                 | MB_TYPE_16x16,
                      MB_TYPE_L1   | MB_TYPE_CBP                 | MB_TYPE_16x16,
                      MB_TYPE_L1   | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
                      MB_TYPE_L0L1                               | MB_TYPE_16x16,
                      MB_TYPE_L0L1 | MB_TYPE_CBP                 | MB_TYPE_16x16,
                      MB_TYPE_L0L1 | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
    0, //stuffing
    MB_TYPE_INTRA4x4                | MB_TYPE_CBP,
    MB_TYPE_INTRA4x4                | MB_TYPE_CBP | MB_TYPE_QUANT,
};

void ff_h263_show_pict_info(MpegEncContext *s){
    if(s->avctx->debug&FF_DEBUG_PICT_INFO){
    av_log(s->avctx, AV_LOG_DEBUG, "qp:%d %c size:%d rnd:%d%s%s%s%s%s%s%s%s%s %d/%d\n",
         s->qscale, av_get_picture_type_char(s->pict_type),
         s->gb.size_in_bits, 1-s->no_rounding,
         s->obmc ? " AP" : "",
         s->umvplus ? " UMV" : "",
         s->h263_long_vectors ? " LONG" : "",
         s->h263_plus ? " +" : "",
         s->h263_aic ? " AIC" : "",
         s->alt_inter_vlc ? " AIV" : "",
         s->modified_quant ? " MQ" : "",
         s->loop_filter ? " LOOP" : "",
         s->h263_slice_structured ? " SS" : "",
         s->avctx->time_base.den, s->avctx->time_base.num
    );
    }
}

/***********************************************/
/* decoding */

VLC ff_h263_intra_MCBPC_vlc;
VLC ff_h263_inter_MCBPC_vlc;
VLC ff_h263_cbpy_vlc;
static VLC mv_vlc;
static VLC h263_mbtype_b_vlc;
static VLC cbpc_b_vlc;

/* init vlcs */

/* XXX: find a better solution to handle static init */
void h263_decode_init_vlc(MpegEncContext *s)
{
    static int done = 0;

    if (!done) {
        done = 1;

        INIT_VLC_STATIC(&ff_h263_intra_MCBPC_vlc, INTRA_MCBPC_VLC_BITS, 9,
                 ff_h263_intra_MCBPC_bits, 1, 1,
                 ff_h263_intra_MCBPC_code, 1, 1, 72);
        INIT_VLC_STATIC(&ff_h263_inter_MCBPC_vlc, INTER_MCBPC_VLC_BITS, 28,
                 ff_h263_inter_MCBPC_bits, 1, 1,
                 ff_h263_inter_MCBPC_code, 1, 1, 198);
        INIT_VLC_STATIC(&ff_h263_cbpy_vlc, CBPY_VLC_BITS, 16,
                 &ff_h263_cbpy_tab[0][1], 2, 1,
                 &ff_h263_cbpy_tab[0][0], 2, 1, 64);
        INIT_VLC_STATIC(&mv_vlc, MV_VLC_BITS, 33,
                 &mvtab[0][1], 2, 1,
                 &mvtab[0][0], 2, 1, 538);
        init_rl(&ff_h263_rl_inter, ff_h263_static_rl_table_store[0]);
        init_rl(&rl_intra_aic, ff_h263_static_rl_table_store[1]);
        INIT_VLC_RL(ff_h263_rl_inter, 554);
        INIT_VLC_RL(rl_intra_aic, 554);
        INIT_VLC_STATIC(&h263_mbtype_b_vlc, H263_MBTYPE_B_VLC_BITS, 15,
                 &h263_mbtype_b_tab[0][1], 2, 1,
                 &h263_mbtype_b_tab[0][0], 2, 1, 80);
        INIT_VLC_STATIC(&cbpc_b_vlc, CBPC_B_VLC_BITS, 4,
                 &cbpc_b_tab[0][1], 2, 1,
                 &cbpc_b_tab[0][0], 2, 1, 8);
    }
}

int ff_h263_decode_mba(MpegEncContext *s)
{
    int i, mb_pos;

    for(i=0; i<6; i++){
        if(s->mb_num-1 <= ff_mba_max[i]) break;
    }
    mb_pos= get_bits(&s->gb, ff_mba_length[i]);
    s->mb_x= mb_pos % s->mb_width;
    s->mb_y= mb_pos / s->mb_width;

    return mb_pos;
}

/**
 * Decode the group of blocks header or slice header.
 * @return <0 if an error occurred
 */
static int h263_decode_gob_header(MpegEncContext *s)
{
    unsigned int val, gob_number;
    int left;

    /* Check for GOB Start Code */
    val = show_bits(&s->gb, 16);
    if(val)
        return -1;

        /* We have a GBSC probably with GSTUFF */
    skip_bits(&s->gb, 16); /* Drop the zeros */
    left= get_bits_left(&s->gb);
    //MN: we must check the bits left or we might end in a infinite loop (or segfault)
    for(;left>13; left--){
        if(get_bits1(&s->gb)) break; /* Seek the '1' bit */
    }
    if(left<=13)
        return -1;

    if(s->h263_slice_structured){
        if(get_bits1(&s->gb)==0)
            return -1;

        ff_h263_decode_mba(s);

        if(s->mb_num > 1583)
            if(get_bits1(&s->gb)==0)
                return -1;

        s->qscale = get_bits(&s->gb, 5); /* SQUANT */
        if(get_bits1(&s->gb)==0)
            return -1;
        skip_bits(&s->gb, 2); /* GFID */
    }else{
        gob_number = get_bits(&s->gb, 5); /* GN */
        s->mb_x= 0;
        s->mb_y= s->gob_index* gob_number;
        skip_bits(&s->gb, 2); /* GFID */
        s->qscale = get_bits(&s->gb, 5); /* GQUANT */
    }

    if(s->mb_y >= s->mb_height)
        return -1;

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

    return 0;
}

/**
 * Find the next resync_marker.
 * @param p pointer to buffer to scan
 * @param end pointer to the end of the buffer
 * @return pointer to the next resync_marker, or end if none was found
 */
const uint8_t *ff_h263_find_resync_marker(const uint8_t *restrict p, const uint8_t * restrict end)
{
    assert(p < end);

    end-=2;
    p++;
    for(;p<end; p+=2){
        if(!*p){
            if     (!p[-1] && p[1]) return p - 1;
            else if(!p[ 1] && p[2]) return p;
        }
    }
    return end+2;
}

/**
 * Decode the group of blocks / video packet header.
 * @return bit position of the resync_marker, or <0 if none was found
 */
int ff_h263_resync(MpegEncContext *s){
    int left, pos, ret;

    if(s->codec_id==CODEC_ID_MPEG4){
        skip_bits1(&s->gb);
        align_get_bits(&s->gb);
    }

    if(show_bits(&s->gb, 16)==0){
        pos= get_bits_count(&s->gb);
        if(CONFIG_MPEG4_DECODER && s->codec_id==CODEC_ID_MPEG4)
            ret= mpeg4_decode_video_packet_header(s);
        else
            ret= h263_decode_gob_header(s);
        if(ret>=0)
            return pos;
    }
    //OK, it's not where it is supposed to be ...
    s->gb= s->last_resync_gb;
    align_get_bits(&s->gb);
    left= get_bits_left(&s->gb);

    for(;left>16+1+5+5; left-=8){
        if(show_bits(&s->gb, 16)==0){
            GetBitContext bak= s->gb;

            pos= get_bits_count(&s->gb);
            if(CONFIG_MPEG4_DECODER && s->codec_id==CODEC_ID_MPEG4)
                ret= mpeg4_decode_video_packet_header(s);
            else
                ret= h263_decode_gob_header(s);
            if(ret>=0)
                return pos;

            s->gb= bak;
        }
        skip_bits(&s->gb, 8);
    }

    return -1;
}

int h263_decode_motion(MpegEncContext * s, int pred, int f_code)
{
    int code, val, sign, shift;
    code = get_vlc2(&s->gb, mv_vlc.table, MV_VLC_BITS, 2);

    if (code == 0)
        return pred;
    if (code < 0)
        return 0xffff;

    sign = get_bits1(&s->gb);
    shift = f_code - 1;
    val = code;
    if (shift) {
        val = (val - 1) << shift;
        val |= get_bits(&s->gb, shift);
        val++;
    }
    if (sign)
        val = -val;
    val += pred;

    /* modulo decoding */
    if (!s->h263_long_vectors) {
        val = sign_extend(val, 5 + f_code);
    } else {
        /* horrible h263 long vector mode */
        if (pred < -31 && val < -63)
            val += 64;
        if (pred > 32 && val > 63)
            val -= 64;

    }
    return val;
}


/* Decode RVLC of H.263+ UMV */
static int h263p_decode_umotion(MpegEncContext * s, int pred)
{
   int code = 0, sign;

   if (get_bits1(&s->gb)) /* Motion difference = 0 */
      return pred;

   code = 2 + get_bits1(&s->gb);

   while (get_bits1(&s->gb))
   {
      code <<= 1;
      code += get_bits1(&s->gb);
   }
   sign = code & 1;
   code >>= 1;

   code = (sign) ? (pred - code) : (pred + code);
   av_dlog(s->avctx,"H.263+ UMV Motion = %d\n", code);
   return code;

}

/**
 * read the next MVs for OBMC. yes this is a ugly hack, feel free to send a patch :)
 */
static void preview_obmc(MpegEncContext *s){
    GetBitContext gb= s->gb;

    int cbpc, i, pred_x, pred_y, mx, my;
    int16_t *mot_val;
    const int xy= s->mb_x + 1 + s->mb_y * s->mb_stride;
    const int stride= s->b8_stride*2;

    for(i=0; i<4; i++)
        s->block_index[i]+= 2;
    for(i=4; i<6; i++)
        s->block_index[i]+= 1;
    s->mb_x++;

    assert(s->pict_type == AV_PICTURE_TYPE_P);

    do{
        if (get_bits1(&s->gb)) {
            /* skip mb */
            mot_val = s->current_picture.f.motion_val[0][s->block_index[0]];
            mot_val[0       ]= mot_val[2       ]=
            mot_val[0+stride]= mot_val[2+stride]= 0;
            mot_val[1       ]= mot_val[3       ]=
            mot_val[1+stride]= mot_val[3+stride]= 0;

            s->current_picture.f.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
            goto end;
        }
        cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);
    }while(cbpc == 20);

    if(cbpc & 4){
        s->current_picture.f.mb_type[xy] = MB_TYPE_INTRA;
    }else{
        get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
        if (cbpc & 8) {
            if(s->modified_quant){
                if(get_bits1(&s->gb)) skip_bits(&s->gb, 1);
                else                  skip_bits(&s->gb, 5);
            }else
                skip_bits(&s->gb, 2);
        }

        if ((cbpc & 16) == 0) {
                s->current_picture.f.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
                /* 16x16 motion prediction */
                mot_val= h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
                if (s->umvplus)
                   mx = h263p_decode_umotion(s, pred_x);
                else
                   mx = h263_decode_motion(s, pred_x, 1);

                if (s->umvplus)
                   my = h263p_decode_umotion(s, pred_y);
                else
                   my = h263_decode_motion(s, pred_y, 1);

                mot_val[0       ]= mot_val[2       ]=
                mot_val[0+stride]= mot_val[2+stride]= mx;
                mot_val[1       ]= mot_val[3       ]=
                mot_val[1+stride]= mot_val[3+stride]= my;
        } else {
            s->current_picture.f.mb_type[xy] = MB_TYPE_8x8 | MB_TYPE_L0;
            for(i=0;i<4;i++) {
                mot_val = h263_pred_motion(s, i, 0, &pred_x, &pred_y);
                if (s->umvplus)
                  mx = h263p_decode_umotion(s, pred_x);
                else
                  mx = h263_decode_motion(s, pred_x, 1);

                if (s->umvplus)
                  my = h263p_decode_umotion(s, pred_y);
                else
                  my = h263_decode_motion(s, pred_y, 1);
                if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
                  skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
                mot_val[0] = mx;
                mot_val[1] = my;
            }
        }
    }
end:

    for(i=0; i<4; i++)
        s->block_index[i]-= 2;
    for(i=4; i<6; i++)
        s->block_index[i]-= 1;
    s->mb_x--;

    s->gb= gb;
}

static void h263_decode_dquant(MpegEncContext *s){
    static const int8_t quant_tab[4] = { -1, -2, 1, 2 };

    if(s->modified_quant){
        if(get_bits1(&s->gb))
            s->qscale= modified_quant_tab[get_bits1(&s->gb)][ s->qscale ];
        else
            s->qscale= get_bits(&s->gb, 5);
    }else
        s->qscale += quant_tab[get_bits(&s->gb, 2)];
    ff_set_qscale(s, s->qscale);
}

static int h263_decode_block(MpegEncContext * s, DCTELEM * block,
                             int n, int coded)
{
    int code, level, i, j, last, run;
    RLTable *rl = &ff_h263_rl_inter;
    const uint8_t *scan_table;
    GetBitContext gb= s->gb;

    scan_table = s->intra_scantable.permutated;
    if (s->h263_aic && s->mb_intra) {
        rl = &rl_intra_aic;
        i = 0;
        if (s->ac_pred) {
            if (s->h263_aic_dir)
                scan_table = s->intra_v_scantable.permutated; /* left */
            else
                scan_table = s->intra_h_scantable.permutated; /* top */
        }
    } else if (s->mb_intra) {
        /* DC coef */
        if(s->codec_id == CODEC_ID_RV10){
#if CONFIG_RV10_DECODER
          if (s->rv10_version == 3 && s->pict_type == AV_PICTURE_TYPE_I) {
            int component, diff;
            component = (n <= 3 ? 0 : n - 4 + 1);
            level = s->last_dc[component];
            if (s->rv10_first_dc_coded[component]) {
                diff = rv_decode_dc(s, n);
                if (diff == 0xffff)
                    return -1;
                level += diff;
                level = level & 0xff; /* handle wrap round */
                s->last_dc[component] = level;
            } else {
                s->rv10_first_dc_coded[component] = 1;
            }
          } else {
                level = get_bits(&s->gb, 8);
                if (level == 255)
                    level = 128;
          }
#endif
        }else{
            level = get_bits(&s->gb, 8);
            if((level&0x7F) == 0){
                av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
                if(s->err_recognition & AV_EF_BITSTREAM)
                    return -1;
            }
            if (level == 255)
                level = 128;
        }
        block[0] = level;
        i = 1;
    } else {
        i = 0;
    }
    if (!coded) {
        if (s->mb_intra && s->h263_aic)
            goto not_coded;
        s->block_last_index[n] = i - 1;
        return 0;
    }
retry:
    for(;;) {
        code = get_vlc2(&s->gb, rl->vlc.table, TEX_VLC_BITS, 2);
        if (code < 0){
            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
            return -1;
        }
        if (code == rl->n) {
            /* escape */
            if (CONFIG_FLV_DECODER && s->h263_flv > 1) {
                ff_flv2_decode_ac_esc(&s->gb, &level, &run, &last);
            } else {
                last = get_bits1(&s->gb);
                run = get_bits(&s->gb, 6);
                level = (int8_t)get_bits(&s->gb, 8);
                if(level == -128){
                    if (s->codec_id == CODEC_ID_RV10) {
                        /* XXX: should patch encoder too */
                        level = get_sbits(&s->gb, 12);
                    }else{
                        level = get_bits(&s->gb, 5);
                        level |= get_sbits(&s->gb, 6)<<5;
                    }
                }
            }
        } else {
            run = rl->table_run[code];
            level = rl->table_level[code];
            last = code >= rl->last;
            if (get_bits1(&s->gb))
                level = -level;
        }
        i += run;
        if (i >= 64){
            if(s->alt_inter_vlc && rl == &ff_h263_rl_inter && !s->mb_intra){
                //Looks like a hack but no, it's the way it is supposed to work ...
                rl = &rl_intra_aic;
                i = 0;
                s->gb= gb;
                s->dsp.clear_block(block);
                goto retry;
            }
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d i:%d\n", s->mb_x, s->mb_y, s->mb_intra);
            return -1;
        }
        j = scan_table[i];
        block[j] = level;
        if (last)
            break;
        i++;
    }
not_coded:
    if (s->mb_intra && s->h263_aic) {
        h263_pred_acdc(s, block, n);
        i = 63;
    }
    s->block_last_index[n] = i;
    return 0;
}

static int h263_skip_b_part(MpegEncContext *s, int cbp)
{
    LOCAL_ALIGNED_16(DCTELEM, dblock, [64]);
    int i, mbi;

    /* we have to set s->mb_intra to zero to decode B-part of PB-frame correctly
     * but real value should be restored in order to be used later (in OBMC condition)
     */
    mbi = s->mb_intra;
    s->mb_intra = 0;
    for (i = 0; i < 6; i++) {
        if (h263_decode_block(s, dblock, i, cbp&32) < 0)
            return -1;
        cbp+=cbp;
    }
    s->mb_intra = mbi;
    return 0;
}

static int h263_get_modb(GetBitContext *gb, int pb_frame, int *cbpb)
{
    int c, mv = 1;

    if (pb_frame < 3) { // h.263 Annex G and i263 PB-frame
        c = get_bits1(gb);
        if (pb_frame == 2 && c)
            mv = !get_bits1(gb);
    } else { // h.263 Annex M improved PB-frame
        mv = get_unary(gb, 0, 4) + 1;
        c = mv & 1;
        mv = !!(mv & 2);
    }
    if(c)
        *cbpb = get_bits(gb, 6);
    return mv;
}

int ff_h263_decode_mb(MpegEncContext *s,
                      DCTELEM block[6][64])
{
    int cbpc, cbpy, i, cbp, pred_x, pred_y, mx, my, dquant;
    int16_t *mot_val;
    const int xy= s->mb_x + s->mb_y * s->mb_stride;
    int cbpb = 0, pb_mv_count = 0;

    assert(!s->h263_pred);

    if (s->pict_type == AV_PICTURE_TYPE_P) {
        do{
            if (get_bits1(&s->gb)) {
                /* skip mb */
                s->mb_intra = 0;
                for(i=0;i<6;i++)
                    s->block_last_index[i] = -1;
                s->mv_dir = MV_DIR_FORWARD;
                s->mv_type = MV_TYPE_16X16;
                s->current_picture.f.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
                s->mv[0][0][0] = 0;
                s->mv[0][0][1] = 0;
                s->mb_skipped = !(s->obmc | s->loop_filter);
                goto end;
            }
            cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);
            if (cbpc < 0){
                av_log(s->avctx, AV_LOG_ERROR, "cbpc damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }
        }while(cbpc == 20);

        s->dsp.clear_blocks(s->block[0]);

        dquant = cbpc & 8;
        s->mb_intra = ((cbpc & 4) != 0);
        if (s->mb_intra) goto intra;

        if(s->pb_frame && get_bits1(&s->gb))
            pb_mv_count = h263_get_modb(&s->gb, s->pb_frame, &cbpb);
        cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);

        if(s->alt_inter_vlc==0 || (cbpc & 3)!=3)
            cbpy ^= 0xF;

        cbp = (cbpc & 3) | (cbpy << 2);
        if (dquant) {
            h263_decode_dquant(s);
        }

        s->mv_dir = MV_DIR_FORWARD;
        if ((cbpc & 16) == 0) {
            s->current_picture.f.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
            /* 16x16 motion prediction */
            s->mv_type = MV_TYPE_16X16;
            h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
            if (s->umvplus)
               mx = h263p_decode_umotion(s, pred_x);
            else
               mx = h263_decode_motion(s, pred_x, 1);

            if (mx >= 0xffff)
                return -1;

            if (s->umvplus)
               my = h263p_decode_umotion(s, pred_y);
            else
               my = h263_decode_motion(s, pred_y, 1);

            if (my >= 0xffff)
                return -1;
            s->mv[0][0][0] = mx;
            s->mv[0][0][1] = my;

            if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
               skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
        } else {
            s->current_picture.f.mb_type[xy] = MB_TYPE_8x8 | MB_TYPE_L0;
            s->mv_type = MV_TYPE_8X8;
            for(i=0;i<4;i++) {
                mot_val = h263_pred_motion(s, i, 0, &pred_x, &pred_y);
                if (s->umvplus)
                  mx = h263p_decode_umotion(s, pred_x);
                else
                  mx = h263_decode_motion(s, pred_x, 1);
                if (mx >= 0xffff)
                    return -1;

                if (s->umvplus)
                  my = h263p_decode_umotion(s, pred_y);
                else
                  my = h263_decode_motion(s, pred_y, 1);
                if (my >= 0xffff)
                    return -1;
                s->mv[0][i][0] = mx;
                s->mv[0][i][1] = my;
                if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
                  skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
                mot_val[0] = mx;
                mot_val[1] = my;
            }
        }
    } else if(s->pict_type==AV_PICTURE_TYPE_B) {
        int mb_type;
        const int stride= s->b8_stride;
        int16_t *mot_val0 = s->current_picture.f.motion_val[0][2 * (s->mb_x + s->mb_y * stride)];
        int16_t *mot_val1 = s->current_picture.f.motion_val[1][2 * (s->mb_x + s->mb_y * stride)];
//        const int mv_xy= s->mb_x + 1 + s->mb_y * s->mb_stride;

        //FIXME ugly
        mot_val0[0       ]= mot_val0[2       ]= mot_val0[0+2*stride]= mot_val0[2+2*stride]=
        mot_val0[1       ]= mot_val0[3       ]= mot_val0[1+2*stride]= mot_val0[3+2*stride]=
        mot_val1[0       ]= mot_val1[2       ]= mot_val1[0+2*stride]= mot_val1[2+2*stride]=
        mot_val1[1       ]= mot_val1[3       ]= mot_val1[1+2*stride]= mot_val1[3+2*stride]= 0;

        do{
            mb_type= get_vlc2(&s->gb, h263_mbtype_b_vlc.table, H263_MBTYPE_B_VLC_BITS, 2);
            if (mb_type < 0){
                av_log(s->avctx, AV_LOG_ERROR, "b mb_type damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }

            mb_type= h263_mb_type_b_map[ mb_type ];
        }while(!mb_type);

        s->mb_intra = IS_INTRA(mb_type);
        if(HAS_CBP(mb_type)){
            s->dsp.clear_blocks(s->block[0]);
            cbpc = get_vlc2(&s->gb, cbpc_b_vlc.table, CBPC_B_VLC_BITS, 1);
            if(s->mb_intra){
                dquant = IS_QUANT(mb_type);
                goto intra;
            }

            cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);

            if (cbpy < 0){
                av_log(s->avctx, AV_LOG_ERROR, "b cbpy damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }

            if(s->alt_inter_vlc==0 || (cbpc & 3)!=3)
                cbpy ^= 0xF;

            cbp = (cbpc & 3) | (cbpy << 2);
        }else
            cbp=0;

        assert(!s->mb_intra);

        if(IS_QUANT(mb_type)){
            h263_decode_dquant(s);
        }

        if(IS_DIRECT(mb_type)){
            s->mv_dir = MV_DIR_FORWARD | MV_DIR_BACKWARD | MV_DIRECT;
            mb_type |= ff_mpeg4_set_direct_mv(s, 0, 0);
        }else{
            s->mv_dir = 0;
            s->mv_type= MV_TYPE_16X16;
//FIXME UMV

            if(USES_LIST(mb_type, 0)){
                int16_t *mot_val= h263_pred_motion(s, 0, 0, &mx, &my);
                s->mv_dir = MV_DIR_FORWARD;

                mx = h263_decode_motion(s, mx, 1);
                my = h263_decode_motion(s, my, 1);

                s->mv[0][0][0] = mx;
                s->mv[0][0][1] = my;
                mot_val[0       ]= mot_val[2       ]= mot_val[0+2*stride]= mot_val[2+2*stride]= mx;
                mot_val[1       ]= mot_val[3       ]= mot_val[1+2*stride]= mot_val[3+2*stride]= my;
            }

            if(USES_LIST(mb_type, 1)){
                int16_t *mot_val= h263_pred_motion(s, 0, 1, &mx, &my);
                s->mv_dir |= MV_DIR_BACKWARD;

                mx = h263_decode_motion(s, mx, 1);
                my = h263_decode_motion(s, my, 1);

                s->mv[1][0][0] = mx;
                s->mv[1][0][1] = my;
                mot_val[0       ]= mot_val[2       ]= mot_val[0+2*stride]= mot_val[2+2*stride]= mx;
                mot_val[1       ]= mot_val[3       ]= mot_val[1+2*stride]= mot_val[3+2*stride]= my;
            }
        }

        s->current_picture.f.mb_type[xy] = mb_type;
    } else { /* I-Frame */
        do{
            cbpc = get_vlc2(&s->gb, ff_h263_intra_MCBPC_vlc.table, INTRA_MCBPC_VLC_BITS, 2);
            if (cbpc < 0){
                av_log(s->avctx, AV_LOG_ERROR, "I cbpc damaged at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }
        }while(cbpc == 8);

        s->dsp.clear_blocks(s->block[0]);

        dquant = cbpc & 4;
        s->mb_intra = 1;
intra:
        s->current_picture.f.mb_type[xy] = MB_TYPE_INTRA;
        if (s->h263_aic) {
            s->ac_pred = get_bits1(&s->gb);
            if(s->ac_pred){
                s->current_picture.f.mb_type[xy] = MB_TYPE_INTRA | MB_TYPE_ACPRED;

                s->h263_aic_dir = get_bits1(&s->gb);
            }
        }else
            s->ac_pred = 0;

        if(s->pb_frame && get_bits1(&s->gb))
            pb_mv_count = h263_get_modb(&s->gb, s->pb_frame, &cbpb);
        cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
        if(cbpy<0){
            av_log(s->avctx, AV_LOG_ERROR, "I cbpy damaged at %d %d\n", s->mb_x, s->mb_y);
            return -1;
        }
        cbp = (cbpc & 3) | (cbpy << 2);
        if (dquant) {
            h263_decode_dquant(s);
        }

        pb_mv_count += !!s->pb_frame;
    }

    while(pb_mv_count--){
        h263_decode_motion(s, 0, 1);
        h263_decode_motion(s, 0, 1);
    }

    /* decode each block */
    for (i = 0; i < 6; i++) {
        if (h263_decode_block(s, block[i], i, cbp&32) < 0)
            return -1;
        cbp+=cbp;
    }

    if(s->pb_frame && h263_skip_b_part(s, cbpb) < 0)
        return -1;
    if(s->obmc && !s->mb_intra){
        if(s->pict_type == AV_PICTURE_TYPE_P && s->mb_x+1<s->mb_width && s->mb_num_left != 1)
            preview_obmc(s);
    }
end:

        /* per-MB end of slice check */
    {
        int v= show_bits(&s->gb, 16);

        if(get_bits_count(&s->gb) + 16 > s->gb.size_in_bits){
            v>>= get_bits_count(&s->gb) + 16 - s->gb.size_in_bits;
        }

        if(v==0)
            return SLICE_END;
    }

    return SLICE_OK;
}

/* most is hardcoded. should extend to handle all h263 streams */
int h263_decode_picture_header(MpegEncContext *s)
{
    int format, width, height, i;
    uint32_t startcode;

    align_get_bits(&s->gb);

    startcode= get_bits(&s->gb, 22-8);

    for(i= get_bits_left(&s->gb); i>24; i-=8) {
        startcode = ((startcode << 8) | get_bits(&s->gb, 8)) & 0x003FFFFF;

        if(startcode == 0x20)
            break;
    }

    if (startcode != 0x20) {
        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
        return -1;
    }
    /* temporal reference */
    i = get_bits(&s->gb, 8); /* picture timestamp */
    if( (s->picture_number&~0xFF)+i < s->picture_number)
        i+= 256;
    s->current_picture_ptr->f.pts =
    s->picture_number= (s->picture_number&~0xFF) + i;

    /* PTYPE starts here */
    if (get_bits1(&s->gb) != 1) {
        /* marker */
        av_log(s->avctx, AV_LOG_ERROR, "Bad marker\n");
        return -1;
    }
    if (get_bits1(&s->gb) != 0) {
        av_log(s->avctx, AV_LOG_ERROR, "Bad H263 id\n");
        return -1;      /* h263 id */
    }
    skip_bits1(&s->gb);         /* split screen off */
    skip_bits1(&s->gb);         /* camera  off */
    skip_bits1(&s->gb);         /* freeze picture release off */

    format = get_bits(&s->gb, 3);
    /*
        0    forbidden
        1    sub-QCIF
        10   QCIF
        7       extended PTYPE (PLUSPTYPE)
    */

    if (format != 7 && format != 6) {
        s->h263_plus = 0;
        /* H.263v1 */
        width = h263_format[format][0];
        height = h263_format[format][1];
        if (!width)
            return -1;

        s->pict_type = AV_PICTURE_TYPE_I + get_bits1(&s->gb);

        s->h263_long_vectors = get_bits1(&s->gb);

        if (get_bits1(&s->gb) != 0) {
            av_log(s->avctx, AV_LOG_ERROR, "H263 SAC not supported\n");
            return -1; /* SAC: off */
        }
        s->obmc= get_bits1(&s->gb); /* Advanced prediction mode */
        s->unrestricted_mv = s->h263_long_vectors || s->obmc;

        s->pb_frame = get_bits1(&s->gb);
        s->chroma_qscale= s->qscale = get_bits(&s->gb, 5);
        skip_bits1(&s->gb); /* Continuous Presence Multipoint mode: off */

        s->width = width;
        s->height = height;
        s->avctx->sample_aspect_ratio= (AVRational){12,11};
        s->avctx->time_base= (AVRational){1001, 30000};
    } else {
        int ufep;

        /* H.263v2 */
        s->h263_plus = 1;
        ufep = get_bits(&s->gb, 3); /* Update Full Extended PTYPE */

        /* ufep other than 0 and 1 are reserved */
        if (ufep == 1) {
            /* OPPTYPE */
            format = get_bits(&s->gb, 3);
            av_dlog(s->avctx, "ufep=1, format: %d\n", format);
            s->custom_pcf= get_bits1(&s->gb);
            s->umvplus = get_bits1(&s->gb); /* Unrestricted Motion Vector */
            if (get_bits1(&s->gb) != 0) {
                av_log(s->avctx, AV_LOG_ERROR, "Syntax-based Arithmetic Coding (SAC) not supported\n");
            }
            s->obmc= get_bits1(&s->gb); /* Advanced prediction mode */
            s->h263_aic = get_bits1(&s->gb); /* Advanced Intra Coding (AIC) */
            s->loop_filter= get_bits1(&s->gb);
            s->unrestricted_mv = s->umvplus || s->obmc || s->loop_filter;

            s->h263_slice_structured= get_bits1(&s->gb);
            if (get_bits1(&s->gb) != 0) {
                av_log(s->avctx, AV_LOG_ERROR, "Reference Picture Selection not supported\n");
            }
            if (get_bits1(&s->gb) != 0) {
                av_log(s->avctx, AV_LOG_ERROR, "Independent Segment Decoding not supported\n");
            }
            s->alt_inter_vlc= get_bits1(&s->gb);
            s->modified_quant= get_bits1(&s->gb);
            if(s->modified_quant)
                s->chroma_qscale_table= ff_h263_chroma_qscale_table;

            skip_bits(&s->gb, 1); /* Prevent start code emulation */

            skip_bits(&s->gb, 3); /* Reserved */
        } else if (ufep != 0) {
            av_log(s->avctx, AV_LOG_ERROR, "Bad UFEP type (%d)\n", ufep);
            return -1;
        }

        /* MPPTYPE */
        s->pict_type = get_bits(&s->gb, 3);
        switch(s->pict_type){
        case 0: s->pict_type= AV_PICTURE_TYPE_I;break;
        case 1: s->pict_type= AV_PICTURE_TYPE_P;break;
        case 2: s->pict_type= AV_PICTURE_TYPE_P;s->pb_frame = 3;break;
        case 3: s->pict_type= AV_PICTURE_TYPE_B;break;
        case 7: s->pict_type= AV_PICTURE_TYPE_I;break; //ZYGO
        default:
            return -1;
        }
        skip_bits(&s->gb, 2);
        s->no_rounding = get_bits1(&s->gb);
        skip_bits(&s->gb, 4);

        /* Get the picture dimensions */
        if (ufep) {
            if (format == 6) {
                /* Custom Picture Format (CPFMT) */
                s->aspect_ratio_info = get_bits(&s->gb, 4);
                av_dlog(s->avctx, "aspect: %d\n", s->aspect_ratio_info);
                /* aspect ratios:
                0 - forbidden
                1 - 1:1
                2 - 12:11 (CIF 4:3)
                3 - 10:11 (525-type 4:3)
                4 - 16:11 (CIF 16:9)
                5 - 40:33 (525-type 16:9)
                6-14 - reserved
                */
                width = (get_bits(&s->gb, 9) + 1) * 4;
                skip_bits1(&s->gb);
                height = get_bits(&s->gb, 9) * 4;
                av_dlog(s->avctx, "\nH.263+ Custom picture: %dx%d\n",width,height);
                if (s->aspect_ratio_info == FF_ASPECT_EXTENDED) {
                    /* aspected dimensions */
                    s->avctx->sample_aspect_ratio.num= get_bits(&s->gb, 8);
                    s->avctx->sample_aspect_ratio.den= get_bits(&s->gb, 8);
                }else{
                    s->avctx->sample_aspect_ratio= ff_h263_pixel_aspect[s->aspect_ratio_info];
                }
            } else {
                width = h263_format[format][0];
                height = h263_format[format][1];
                s->avctx->sample_aspect_ratio= (AVRational){12,11};
            }
            if ((width == 0) || (height == 0))
                return -1;
            s->width = width;
            s->height = height;

            if(s->custom_pcf){
                int gcd;
                s->avctx->time_base.den= 1800000;
                s->avctx->time_base.num= 1000 + get_bits1(&s->gb);
                s->avctx->time_base.num*= get_bits(&s->gb, 7);
                if(s->avctx->time_base.num == 0){
                    av_log(s, AV_LOG_ERROR, "zero framerate\n");
                    return -1;
                }
                gcd= av_gcd(s->avctx->time_base.den, s->avctx->time_base.num);
                s->avctx->time_base.den /= gcd;
                s->avctx->time_base.num /= gcd;
            }else{
                s->avctx->time_base= (AVRational){1001, 30000};
            }
        }

        if(s->custom_pcf){
            skip_bits(&s->gb, 2); //extended Temporal reference
        }

        if (ufep) {
            if (s->umvplus) {
                if(get_bits1(&s->gb)==0) /* Unlimited Unrestricted Motion Vectors Indicator (UUI) */
                    skip_bits1(&s->gb);
            }
            if(s->h263_slice_structured){
                if (get_bits1(&s->gb) != 0) {
                    av_log(s->avctx, AV_LOG_ERROR, "rectangular slices not supported\n");
                }
                if (get_bits1(&s->gb) != 0) {
                    av_log(s->avctx, AV_LOG_ERROR, "unordered slices not supported\n");
                }
            }
        }

        s->qscale = get_bits(&s->gb, 5);
    }

    s->mb_width = (s->width  + 15) / 16;
    s->mb_height = (s->height  + 15) / 16;
    s->mb_num = s->mb_width * s->mb_height;

    if (s->pb_frame) {
        skip_bits(&s->gb, 3); /* Temporal reference for B-pictures */
        if (s->custom_pcf)
            skip_bits(&s->gb, 2); //extended Temporal reference
        skip_bits(&s->gb, 2); /* Quantization information for B-pictures */
    }

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

    if(s->h263_slice_structured){
        if (get_bits1(&s->gb) != 1) {
            av_log(s->avctx, AV_LOG_ERROR, "SEPB1 marker missing\n");
            return -1;
        }

        ff_h263_decode_mba(s);

        if (get_bits1(&s->gb) != 1) {
            av_log(s->avctx, AV_LOG_ERROR, "SEPB2 marker missing\n");
            return -1;
        }
    }
    s->f_code = 1;

    if(s->h263_aic){
         s->y_dc_scale_table=
         s->c_dc_scale_table= ff_aic_dc_scale_table;
    }else{
        s->y_dc_scale_table=
        s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
    }

        ff_h263_show_pict_info(s);
    if (s->pict_type == AV_PICTURE_TYPE_I && s->codec_tag == AV_RL32("ZYGO")){
        int i,j;
        for(i=0; i<85; i++) av_log(s->avctx, AV_LOG_DEBUG, "%d", get_bits1(&s->gb));
        av_log(s->avctx, AV_LOG_DEBUG, "\n");
        for(i=0; i<13; i++){
            for(j=0; j<3; j++){
                int v= get_bits(&s->gb, 8);
                v |= get_sbits(&s->gb, 8)<<8;
                av_log(s->avctx, AV_LOG_DEBUG, " %5d", v);
            }
            av_log(s->avctx, AV_LOG_DEBUG, "\n");
        }
        for(i=0; i<50; i++) av_log(s->avctx, AV_LOG_DEBUG, "%d", get_bits1(&s->gb));
    }

    return 0;
}