h261dec, ituh263dec: Avoid unnecessary -1 inside inner loop.
[ffmpeg.git] / libavcodec / ituh263dec.c
1 /*
2  * ITU H263 bitstream decoder
3  * Copyright (c) 2000,2001 Fabrice Bellard
4  * H263+ support.
5  * Copyright (c) 2001 Juan J. Sierralta P
6  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
7  *
8  * This file is part of FFmpeg.
9  *
10  * FFmpeg is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU Lesser General Public
12  * License as published by the Free Software Foundation; either
13  * version 2.1 of the License, or (at your option) any later version.
14  *
15  * FFmpeg is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18  * Lesser General Public License for more details.
19  *
20  * You should have received a copy of the GNU Lesser General Public
21  * License along with FFmpeg; if not, write to the Free Software
22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23  */
24
25 /**
26  * @file
27  * h263 decoder.
28  */
29
30 #define UNCHECKED_BITSTREAM_READER 1
31 #include <limits.h>
32
33 #include "libavutil/attributes.h"
34 #include "libavutil/internal.h"
35 #include "libavutil/mathematics.h"
36 #include "avcodec.h"
37 #include "mpegvideo.h"
38 #include "h263.h"
39 #include "mathops.h"
40 #include "mpegutils.h"
41 #include "unary.h"
42 #include "flv.h"
43 #include "mpeg4video.h"
44
45 // The defines below define the number of bits that are read at once for
46 // reading vlc values. Changing these may improve speed and data cache needs
47 // be aware though that decreasing them may need the number of stages that is
48 // passed to get_vlc* to be increased.
49 #define MV_VLC_BITS 9
50 #define H263_MBTYPE_B_VLC_BITS 6
51 #define CBPC_B_VLC_BITS 3
52
53 static const int h263_mb_type_b_map[15]= {
54     MB_TYPE_DIRECT2 | MB_TYPE_L0L1,
55     MB_TYPE_DIRECT2 | MB_TYPE_L0L1 | MB_TYPE_CBP,
56     MB_TYPE_DIRECT2 | MB_TYPE_L0L1 | MB_TYPE_CBP | MB_TYPE_QUANT,
57                       MB_TYPE_L0                                 | MB_TYPE_16x16,
58                       MB_TYPE_L0   | MB_TYPE_CBP                 | MB_TYPE_16x16,
59                       MB_TYPE_L0   | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
60                       MB_TYPE_L1                                 | MB_TYPE_16x16,
61                       MB_TYPE_L1   | MB_TYPE_CBP                 | MB_TYPE_16x16,
62                       MB_TYPE_L1   | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
63                       MB_TYPE_L0L1                               | MB_TYPE_16x16,
64                       MB_TYPE_L0L1 | MB_TYPE_CBP                 | MB_TYPE_16x16,
65                       MB_TYPE_L0L1 | MB_TYPE_CBP | MB_TYPE_QUANT | MB_TYPE_16x16,
66     0, //stuffing
67     MB_TYPE_INTRA4x4                | MB_TYPE_CBP,
68     MB_TYPE_INTRA4x4                | MB_TYPE_CBP | MB_TYPE_QUANT,
69 };
70
71 void ff_h263_show_pict_info(MpegEncContext *s){
72     if(s->avctx->debug&FF_DEBUG_PICT_INFO){
73     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",
74          s->qscale, av_get_picture_type_char(s->pict_type),
75          s->gb.size_in_bits, 1-s->no_rounding,
76          s->obmc ? " AP" : "",
77          s->umvplus ? " UMV" : "",
78          s->h263_long_vectors ? " LONG" : "",
79          s->h263_plus ? " +" : "",
80          s->h263_aic ? " AIC" : "",
81          s->alt_inter_vlc ? " AIV" : "",
82          s->modified_quant ? " MQ" : "",
83          s->loop_filter ? " LOOP" : "",
84          s->h263_slice_structured ? " SS" : "",
85          s->avctx->time_base.den, s->avctx->time_base.num
86     );
87     }
88 }
89
90 /***********************************************/
91 /* decoding */
92
93 VLC ff_h263_intra_MCBPC_vlc;
94 VLC ff_h263_inter_MCBPC_vlc;
95 VLC ff_h263_cbpy_vlc;
96 static VLC mv_vlc;
97 static VLC h263_mbtype_b_vlc;
98 static VLC cbpc_b_vlc;
99
100 /* init vlcs */
101
102 /* XXX: find a better solution to handle static init */
103 av_cold void ff_h263_decode_init_vlc(void)
104 {
105     static volatile int done = 0;
106
107     if (!done) {
108         INIT_VLC_STATIC(&ff_h263_intra_MCBPC_vlc, INTRA_MCBPC_VLC_BITS, 9,
109                  ff_h263_intra_MCBPC_bits, 1, 1,
110                  ff_h263_intra_MCBPC_code, 1, 1, 72);
111         INIT_VLC_STATIC(&ff_h263_inter_MCBPC_vlc, INTER_MCBPC_VLC_BITS, 28,
112                  ff_h263_inter_MCBPC_bits, 1, 1,
113                  ff_h263_inter_MCBPC_code, 1, 1, 198);
114         INIT_VLC_STATIC(&ff_h263_cbpy_vlc, CBPY_VLC_BITS, 16,
115                  &ff_h263_cbpy_tab[0][1], 2, 1,
116                  &ff_h263_cbpy_tab[0][0], 2, 1, 64);
117         INIT_VLC_STATIC(&mv_vlc, MV_VLC_BITS, 33,
118                  &ff_mvtab[0][1], 2, 1,
119                  &ff_mvtab[0][0], 2, 1, 538);
120         ff_init_rl(&ff_h263_rl_inter, ff_h263_static_rl_table_store[0]);
121         ff_init_rl(&ff_rl_intra_aic, ff_h263_static_rl_table_store[1]);
122         INIT_VLC_RL(ff_h263_rl_inter, 554);
123         INIT_VLC_RL(ff_rl_intra_aic, 554);
124         INIT_VLC_STATIC(&h263_mbtype_b_vlc, H263_MBTYPE_B_VLC_BITS, 15,
125                  &ff_h263_mbtype_b_tab[0][1], 2, 1,
126                  &ff_h263_mbtype_b_tab[0][0], 2, 1, 80);
127         INIT_VLC_STATIC(&cbpc_b_vlc, CBPC_B_VLC_BITS, 4,
128                  &ff_cbpc_b_tab[0][1], 2, 1,
129                  &ff_cbpc_b_tab[0][0], 2, 1, 8);
130         done = 1;
131     }
132 }
133
134 int ff_h263_decode_mba(MpegEncContext *s)
135 {
136     int i, mb_pos;
137
138     for(i=0; i<6; i++){
139         if(s->mb_num-1 <= ff_mba_max[i]) break;
140     }
141     mb_pos= get_bits(&s->gb, ff_mba_length[i]);
142     s->mb_x= mb_pos % s->mb_width;
143     s->mb_y= mb_pos / s->mb_width;
144
145     return mb_pos;
146 }
147
148 /**
149  * Decode the group of blocks header or slice header.
150  * @return <0 if an error occurred
151  */
152 static int h263_decode_gob_header(MpegEncContext *s)
153 {
154     unsigned int val, gob_number;
155     int left;
156
157     /* Check for GOB Start Code */
158     val = show_bits(&s->gb, 16);
159     if(val)
160         return -1;
161
162         /* We have a GBSC probably with GSTUFF */
163     skip_bits(&s->gb, 16); /* Drop the zeros */
164     left= get_bits_left(&s->gb);
165     //MN: we must check the bits left or we might end in a infinite loop (or segfault)
166     for(;left>13; left--){
167         if(get_bits1(&s->gb)) break; /* Seek the '1' bit */
168     }
169     if(left<=13)
170         return -1;
171
172     if(s->h263_slice_structured){
173         if(get_bits1(&s->gb)==0)
174             return -1;
175
176         ff_h263_decode_mba(s);
177
178         if(s->mb_num > 1583)
179             if(get_bits1(&s->gb)==0)
180                 return -1;
181
182         s->qscale = get_bits(&s->gb, 5); /* SQUANT */
183         if(get_bits1(&s->gb)==0)
184             return -1;
185         skip_bits(&s->gb, 2); /* GFID */
186     }else{
187         gob_number = get_bits(&s->gb, 5); /* GN */
188         s->mb_x= 0;
189         s->mb_y= s->gob_index* gob_number;
190         skip_bits(&s->gb, 2); /* GFID */
191         s->qscale = get_bits(&s->gb, 5); /* GQUANT */
192     }
193
194     if(s->mb_y >= s->mb_height)
195         return -1;
196
197     if(s->qscale==0)
198         return -1;
199
200     return 0;
201 }
202
203 /**
204  * Decode the group of blocks / video packet header.
205  * @return bit position of the resync_marker, or <0 if none was found
206  */
207 int ff_h263_resync(MpegEncContext *s){
208     int left, pos, ret;
209
210     if(s->codec_id==AV_CODEC_ID_MPEG4){
211         skip_bits1(&s->gb);
212         align_get_bits(&s->gb);
213     }
214
215     if(show_bits(&s->gb, 16)==0){
216         pos= get_bits_count(&s->gb);
217         if(CONFIG_MPEG4_DECODER && s->codec_id==AV_CODEC_ID_MPEG4)
218             ret= ff_mpeg4_decode_video_packet_header(s->avctx->priv_data);
219         else
220             ret= h263_decode_gob_header(s);
221         if(ret>=0)
222             return pos;
223     }
224     //OK, it's not where it is supposed to be ...
225     s->gb= s->last_resync_gb;
226     align_get_bits(&s->gb);
227     left= get_bits_left(&s->gb);
228
229     for(;left>16+1+5+5; left-=8){
230         if(show_bits(&s->gb, 16)==0){
231             GetBitContext bak= s->gb;
232
233             pos= get_bits_count(&s->gb);
234             if(CONFIG_MPEG4_DECODER && s->codec_id==AV_CODEC_ID_MPEG4)
235                 ret= ff_mpeg4_decode_video_packet_header(s->avctx->priv_data);
236             else
237                 ret= h263_decode_gob_header(s);
238             if(ret>=0)
239                 return pos;
240
241             s->gb= bak;
242         }
243         skip_bits(&s->gb, 8);
244     }
245
246     return -1;
247 }
248
249 int ff_h263_decode_motion(MpegEncContext * s, int pred, int f_code)
250 {
251     int code, val, sign, shift;
252     code = get_vlc2(&s->gb, mv_vlc.table, MV_VLC_BITS, 2);
253
254     if (code == 0)
255         return pred;
256     if (code < 0)
257         return 0xffff;
258
259     sign = get_bits1(&s->gb);
260     shift = f_code - 1;
261     val = code;
262     if (shift) {
263         val = (val - 1) << shift;
264         val |= get_bits(&s->gb, shift);
265         val++;
266     }
267     if (sign)
268         val = -val;
269     val += pred;
270
271     /* modulo decoding */
272     if (!s->h263_long_vectors) {
273         val = sign_extend(val, 5 + f_code);
274     } else {
275         /* horrible h263 long vector mode */
276         if (pred < -31 && val < -63)
277             val += 64;
278         if (pred > 32 && val > 63)
279             val -= 64;
280
281     }
282     return val;
283 }
284
285
286 /* Decode RVLC of H.263+ UMV */
287 static int h263p_decode_umotion(MpegEncContext * s, int pred)
288 {
289    int code = 0, sign;
290
291    if (get_bits1(&s->gb)) /* Motion difference = 0 */
292       return pred;
293
294    code = 2 + get_bits1(&s->gb);
295
296    while (get_bits1(&s->gb))
297    {
298       code <<= 1;
299       code += get_bits1(&s->gb);
300    }
301    sign = code & 1;
302    code >>= 1;
303
304    code = (sign) ? (pred - code) : (pred + code);
305    av_dlog(s->avctx,"H.263+ UMV Motion = %d\n", code);
306    return code;
307
308 }
309
310 /**
311  * read the next MVs for OBMC. yes this is a ugly hack, feel free to send a patch :)
312  */
313 static void preview_obmc(MpegEncContext *s){
314     GetBitContext gb= s->gb;
315
316     int cbpc, i, pred_x, pred_y, mx, my;
317     int16_t *mot_val;
318     const int xy= s->mb_x + 1 + s->mb_y * s->mb_stride;
319     const int stride= s->b8_stride*2;
320
321     for(i=0; i<4; i++)
322         s->block_index[i]+= 2;
323     for(i=4; i<6; i++)
324         s->block_index[i]+= 1;
325     s->mb_x++;
326
327     av_assert2(s->pict_type == AV_PICTURE_TYPE_P);
328
329     do{
330         if (get_bits1(&s->gb)) {
331             /* skip mb */
332             mot_val = s->current_picture.motion_val[0][s->block_index[0]];
333             mot_val[0       ]= mot_val[2       ]=
334             mot_val[0+stride]= mot_val[2+stride]= 0;
335             mot_val[1       ]= mot_val[3       ]=
336             mot_val[1+stride]= mot_val[3+stride]= 0;
337
338             s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
339             goto end;
340         }
341         cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);
342     }while(cbpc == 20);
343
344     if(cbpc & 4){
345         s->current_picture.mb_type[xy] = MB_TYPE_INTRA;
346     }else{
347         get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
348         if (cbpc & 8) {
349             if(s->modified_quant){
350                 if(get_bits1(&s->gb)) skip_bits(&s->gb, 1);
351                 else                  skip_bits(&s->gb, 5);
352             }else
353                 skip_bits(&s->gb, 2);
354         }
355
356         if ((cbpc & 16) == 0) {
357                 s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
358                 /* 16x16 motion prediction */
359                 mot_val= ff_h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
360                 if (s->umvplus)
361                    mx = h263p_decode_umotion(s, pred_x);
362                 else
363                    mx = ff_h263_decode_motion(s, pred_x, 1);
364
365                 if (s->umvplus)
366                    my = h263p_decode_umotion(s, pred_y);
367                 else
368                    my = ff_h263_decode_motion(s, pred_y, 1);
369
370                 mot_val[0       ]= mot_val[2       ]=
371                 mot_val[0+stride]= mot_val[2+stride]= mx;
372                 mot_val[1       ]= mot_val[3       ]=
373                 mot_val[1+stride]= mot_val[3+stride]= my;
374         } else {
375             s->current_picture.mb_type[xy] = MB_TYPE_8x8 | MB_TYPE_L0;
376             for(i=0;i<4;i++) {
377                 mot_val = ff_h263_pred_motion(s, i, 0, &pred_x, &pred_y);
378                 if (s->umvplus)
379                   mx = h263p_decode_umotion(s, pred_x);
380                 else
381                   mx = ff_h263_decode_motion(s, pred_x, 1);
382
383                 if (s->umvplus)
384                   my = h263p_decode_umotion(s, pred_y);
385                 else
386                   my = ff_h263_decode_motion(s, pred_y, 1);
387                 if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
388                   skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
389                 mot_val[0] = mx;
390                 mot_val[1] = my;
391             }
392         }
393     }
394 end:
395
396     for(i=0; i<4; i++)
397         s->block_index[i]-= 2;
398     for(i=4; i<6; i++)
399         s->block_index[i]-= 1;
400     s->mb_x--;
401
402     s->gb= gb;
403 }
404
405 static void h263_decode_dquant(MpegEncContext *s){
406     static const int8_t quant_tab[4] = { -1, -2, 1, 2 };
407
408     if(s->modified_quant){
409         if(get_bits1(&s->gb))
410             s->qscale= ff_modified_quant_tab[get_bits1(&s->gb)][ s->qscale ];
411         else
412             s->qscale= get_bits(&s->gb, 5);
413     }else
414         s->qscale += quant_tab[get_bits(&s->gb, 2)];
415     ff_set_qscale(s, s->qscale);
416 }
417
418 static int h263_decode_block(MpegEncContext * s, int16_t * block,
419                              int n, int coded)
420 {
421     int level, i, j, run;
422     RLTable *rl = &ff_h263_rl_inter;
423     const uint8_t *scan_table;
424     GetBitContext gb= s->gb;
425
426     scan_table = s->intra_scantable.permutated;
427     if (s->h263_aic && s->mb_intra) {
428         rl = &ff_rl_intra_aic;
429         i = 0;
430         if (s->ac_pred) {
431             if (s->h263_aic_dir)
432                 scan_table = s->intra_v_scantable.permutated; /* left */
433             else
434                 scan_table = s->intra_h_scantable.permutated; /* top */
435         }
436     } else if (s->mb_intra) {
437         /* DC coef */
438         if(s->codec_id == AV_CODEC_ID_RV10){
439 #if CONFIG_RV10_DECODER
440           if (s->rv10_version == 3 && s->pict_type == AV_PICTURE_TYPE_I) {
441             int component, diff;
442             component = (n <= 3 ? 0 : n - 4 + 1);
443             level = s->last_dc[component];
444             if (s->rv10_first_dc_coded[component]) {
445                 diff = ff_rv_decode_dc(s, n);
446                 if (diff == 0xffff)
447                     return -1;
448                 level += diff;
449                 level = level & 0xff; /* handle wrap round */
450                 s->last_dc[component] = level;
451             } else {
452                 s->rv10_first_dc_coded[component] = 1;
453             }
454           } else {
455                 level = get_bits(&s->gb, 8);
456                 if (level == 255)
457                     level = 128;
458           }
459 #endif
460         }else{
461             level = get_bits(&s->gb, 8);
462             if((level&0x7F) == 0){
463                 av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
464                 if(s->err_recognition & (AV_EF_BITSTREAM|AV_EF_COMPLIANT))
465                     return -1;
466             }
467             if (level == 255)
468                 level = 128;
469         }
470         block[0] = level;
471         i = 1;
472     } else {
473         i = 0;
474     }
475     if (!coded) {
476         if (s->mb_intra && s->h263_aic)
477             goto not_coded;
478         s->block_last_index[n] = i - 1;
479         return 0;
480     }
481 retry:
482     {
483     OPEN_READER(re, &s->gb);
484     i--; // offset by -1 to allow direct indexing of scan_table
485     for(;;) {
486         UPDATE_CACHE(re, &s->gb);
487         GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0);
488         if (run == 66 && level){
489             av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
490             return -1;
491         }
492         if (run == 66) {
493             /* escape */
494             if (CONFIG_FLV_DECODER && s->h263_flv > 1) {
495                 int is11 = SHOW_UBITS(re, &s->gb, 1);
496                 SKIP_CACHE(re, &s->gb, 1);
497                 run = SHOW_UBITS(re, &s->gb, 7) + 1;
498                 if (is11) {
499                     SKIP_COUNTER(re, &s->gb, 1 + 7);
500                     UPDATE_CACHE(re, &s->gb);
501                     level = SHOW_SBITS(re, &s->gb, 11);
502                     SKIP_COUNTER(re, &s->gb, 11);
503                 } else {
504                     SKIP_CACHE(re, &s->gb, 7);
505                     level = SHOW_SBITS(re, &s->gb, 7);
506                     SKIP_COUNTER(re, &s->gb, 1 + 7 + 7);
507                 }
508             } else {
509                 run = SHOW_UBITS(re, &s->gb, 7) + 1;
510                 SKIP_CACHE(re, &s->gb, 7);
511                 level = (int8_t)SHOW_UBITS(re, &s->gb, 8);
512                 SKIP_COUNTER(re, &s->gb, 7 + 8);
513                 if(level == -128){
514                     UPDATE_CACHE(re, &s->gb);
515                     if (s->codec_id == AV_CODEC_ID_RV10) {
516                         /* XXX: should patch encoder too */
517                         level = SHOW_SBITS(re, &s->gb, 12);
518                         SKIP_COUNTER(re, &s->gb, 12);
519                     }else{
520                         level = SHOW_UBITS(re, &s->gb, 5);
521                         SKIP_CACHE(re, &s->gb, 5);
522                         level |= SHOW_SBITS(re, &s->gb, 6)<<5;
523                         SKIP_COUNTER(re, &s->gb, 5 + 6);
524                     }
525                 }
526             }
527         } else {
528             if (SHOW_UBITS(re, &s->gb, 1))
529                 level = -level;
530             SKIP_COUNTER(re, &s->gb, 1);
531         }
532         i += run;
533         if (i >= 64){
534             // redo update without last flag, revert -1 offset
535             i = i - run + ((run-1)&63) + 1;
536             if (i < 64) {
537                 // only last marker, no overrun
538                 block[scan_table[i]] = level;
539                 break;
540             }
541             if(s->alt_inter_vlc && rl == &ff_h263_rl_inter && !s->mb_intra){
542                 CLOSE_READER(re, &s->gb);
543                 //Looks like a hack but no, it's the way it is supposed to work ...
544                 rl = &ff_rl_intra_aic;
545                 i = 0;
546                 s->gb= gb;
547                 s->bdsp.clear_block(block);
548                 goto retry;
549             }
550             av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d i:%d\n", s->mb_x, s->mb_y, s->mb_intra);
551             return -1;
552         }
553         j = scan_table[i];
554         block[j] = level;
555     }
556     CLOSE_READER(re, &s->gb);
557     }
558 not_coded:
559     if (s->mb_intra && s->h263_aic) {
560         ff_h263_pred_acdc(s, block, n);
561         i = 63;
562     }
563     s->block_last_index[n] = i;
564     return 0;
565 }
566
567 static int h263_skip_b_part(MpegEncContext *s, int cbp)
568 {
569     LOCAL_ALIGNED_16(int16_t, dblock, [64]);
570     int i, mbi;
571     int bli[6];
572
573     /* we have to set s->mb_intra to zero to decode B-part of PB-frame correctly
574      * but real value should be restored in order to be used later (in OBMC condition)
575      */
576     mbi = s->mb_intra;
577     memcpy(bli, s->block_last_index, sizeof(bli));
578     s->mb_intra = 0;
579     for (i = 0; i < 6; i++) {
580         if (h263_decode_block(s, dblock, i, cbp&32) < 0)
581             return -1;
582         cbp+=cbp;
583     }
584     s->mb_intra = mbi;
585     memcpy(s->block_last_index, bli, sizeof(bli));
586     return 0;
587 }
588
589 static int h263_get_modb(GetBitContext *gb, int pb_frame, int *cbpb)
590 {
591     int c, mv = 1;
592
593     if (pb_frame < 3) { // h.263 Annex G and i263 PB-frame
594         c = get_bits1(gb);
595         if (pb_frame == 2 && c)
596             mv = !get_bits1(gb);
597     } else { // h.263 Annex M improved PB-frame
598         mv = get_unary(gb, 0, 4) + 1;
599         c = mv & 1;
600         mv = !!(mv & 2);
601     }
602     if(c)
603         *cbpb = get_bits(gb, 6);
604     return mv;
605 }
606
607 int ff_h263_decode_mb(MpegEncContext *s,
608                       int16_t block[6][64])
609 {
610     int cbpc, cbpy, i, cbp, pred_x, pred_y, mx, my, dquant;
611     int16_t *mot_val;
612     const int xy= s->mb_x + s->mb_y * s->mb_stride;
613     int cbpb = 0, pb_mv_count = 0;
614
615     av_assert2(!s->h263_pred);
616
617     if (s->pict_type == AV_PICTURE_TYPE_P) {
618         do{
619             if (get_bits1(&s->gb)) {
620                 /* skip mb */
621                 s->mb_intra = 0;
622                 for(i=0;i<6;i++)
623                     s->block_last_index[i] = -1;
624                 s->mv_dir = MV_DIR_FORWARD;
625                 s->mv_type = MV_TYPE_16X16;
626                 s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
627                 s->mv[0][0][0] = 0;
628                 s->mv[0][0][1] = 0;
629                 s->mb_skipped = !(s->obmc | s->loop_filter);
630                 goto end;
631             }
632             cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);
633             if (cbpc < 0){
634                 av_log(s->avctx, AV_LOG_ERROR, "cbpc damaged at %d %d\n", s->mb_x, s->mb_y);
635                 return -1;
636             }
637         }while(cbpc == 20);
638
639         s->bdsp.clear_blocks(s->block[0]);
640
641         dquant = cbpc & 8;
642         s->mb_intra = ((cbpc & 4) != 0);
643         if (s->mb_intra) goto intra;
644
645         if(s->pb_frame && get_bits1(&s->gb))
646             pb_mv_count = h263_get_modb(&s->gb, s->pb_frame, &cbpb);
647         cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
648
649         if(s->alt_inter_vlc==0 || (cbpc & 3)!=3)
650             cbpy ^= 0xF;
651
652         cbp = (cbpc & 3) | (cbpy << 2);
653         if (dquant) {
654             h263_decode_dquant(s);
655         }
656
657         s->mv_dir = MV_DIR_FORWARD;
658         if ((cbpc & 16) == 0) {
659             s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
660             /* 16x16 motion prediction */
661             s->mv_type = MV_TYPE_16X16;
662             ff_h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
663             if (s->umvplus)
664                mx = h263p_decode_umotion(s, pred_x);
665             else
666                mx = ff_h263_decode_motion(s, pred_x, 1);
667
668             if (mx >= 0xffff)
669                 return -1;
670
671             if (s->umvplus)
672                my = h263p_decode_umotion(s, pred_y);
673             else
674                my = ff_h263_decode_motion(s, pred_y, 1);
675
676             if (my >= 0xffff)
677                 return -1;
678             s->mv[0][0][0] = mx;
679             s->mv[0][0][1] = my;
680
681             if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
682                skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
683         } else {
684             s->current_picture.mb_type[xy] = MB_TYPE_8x8 | MB_TYPE_L0;
685             s->mv_type = MV_TYPE_8X8;
686             for(i=0;i<4;i++) {
687                 mot_val = ff_h263_pred_motion(s, i, 0, &pred_x, &pred_y);
688                 if (s->umvplus)
689                   mx = h263p_decode_umotion(s, pred_x);
690                 else
691                   mx = ff_h263_decode_motion(s, pred_x, 1);
692                 if (mx >= 0xffff)
693                     return -1;
694
695                 if (s->umvplus)
696                   my = h263p_decode_umotion(s, pred_y);
697                 else
698                   my = ff_h263_decode_motion(s, pred_y, 1);
699                 if (my >= 0xffff)
700                     return -1;
701                 s->mv[0][i][0] = mx;
702                 s->mv[0][i][1] = my;
703                 if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
704                   skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
705                 mot_val[0] = mx;
706                 mot_val[1] = my;
707             }
708         }
709     } else if(s->pict_type==AV_PICTURE_TYPE_B) {
710         int mb_type;
711         const int stride= s->b8_stride;
712         int16_t *mot_val0 = s->current_picture.motion_val[0][2 * (s->mb_x + s->mb_y * stride)];
713         int16_t *mot_val1 = s->current_picture.motion_val[1][2 * (s->mb_x + s->mb_y * stride)];
714 //        const int mv_xy= s->mb_x + 1 + s->mb_y * s->mb_stride;
715
716         //FIXME ugly
717         mot_val0[0       ]= mot_val0[2       ]= mot_val0[0+2*stride]= mot_val0[2+2*stride]=
718         mot_val0[1       ]= mot_val0[3       ]= mot_val0[1+2*stride]= mot_val0[3+2*stride]=
719         mot_val1[0       ]= mot_val1[2       ]= mot_val1[0+2*stride]= mot_val1[2+2*stride]=
720         mot_val1[1       ]= mot_val1[3       ]= mot_val1[1+2*stride]= mot_val1[3+2*stride]= 0;
721
722         do{
723             mb_type= get_vlc2(&s->gb, h263_mbtype_b_vlc.table, H263_MBTYPE_B_VLC_BITS, 2);
724             if (mb_type < 0){
725                 av_log(s->avctx, AV_LOG_ERROR, "b mb_type damaged at %d %d\n", s->mb_x, s->mb_y);
726                 return -1;
727             }
728
729             mb_type= h263_mb_type_b_map[ mb_type ];
730         }while(!mb_type);
731
732         s->mb_intra = IS_INTRA(mb_type);
733         if(HAS_CBP(mb_type)){
734             s->bdsp.clear_blocks(s->block[0]);
735             cbpc = get_vlc2(&s->gb, cbpc_b_vlc.table, CBPC_B_VLC_BITS, 1);
736             if(s->mb_intra){
737                 dquant = IS_QUANT(mb_type);
738                 goto intra;
739             }
740
741             cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
742
743             if (cbpy < 0){
744                 av_log(s->avctx, AV_LOG_ERROR, "b cbpy damaged at %d %d\n", s->mb_x, s->mb_y);
745                 return -1;
746             }
747
748             if(s->alt_inter_vlc==0 || (cbpc & 3)!=3)
749                 cbpy ^= 0xF;
750
751             cbp = (cbpc & 3) | (cbpy << 2);
752         }else
753             cbp=0;
754
755         av_assert2(!s->mb_intra);
756
757         if(IS_QUANT(mb_type)){
758             h263_decode_dquant(s);
759         }
760
761         if(IS_DIRECT(mb_type)){
762             s->mv_dir = MV_DIR_FORWARD | MV_DIR_BACKWARD | MV_DIRECT;
763             mb_type |= ff_mpeg4_set_direct_mv(s, 0, 0);
764         }else{
765             s->mv_dir = 0;
766             s->mv_type= MV_TYPE_16X16;
767 //FIXME UMV
768
769             if(USES_LIST(mb_type, 0)){
770                 int16_t *mot_val= ff_h263_pred_motion(s, 0, 0, &mx, &my);
771                 s->mv_dir = MV_DIR_FORWARD;
772
773                 mx = ff_h263_decode_motion(s, mx, 1);
774                 my = ff_h263_decode_motion(s, my, 1);
775
776                 s->mv[0][0][0] = mx;
777                 s->mv[0][0][1] = my;
778                 mot_val[0       ]= mot_val[2       ]= mot_val[0+2*stride]= mot_val[2+2*stride]= mx;
779                 mot_val[1       ]= mot_val[3       ]= mot_val[1+2*stride]= mot_val[3+2*stride]= my;
780             }
781
782             if(USES_LIST(mb_type, 1)){
783                 int16_t *mot_val= ff_h263_pred_motion(s, 0, 1, &mx, &my);
784                 s->mv_dir |= MV_DIR_BACKWARD;
785
786                 mx = ff_h263_decode_motion(s, mx, 1);
787                 my = ff_h263_decode_motion(s, my, 1);
788
789                 s->mv[1][0][0] = mx;
790                 s->mv[1][0][1] = my;
791                 mot_val[0       ]= mot_val[2       ]= mot_val[0+2*stride]= mot_val[2+2*stride]= mx;
792                 mot_val[1       ]= mot_val[3       ]= mot_val[1+2*stride]= mot_val[3+2*stride]= my;
793             }
794         }
795
796         s->current_picture.mb_type[xy] = mb_type;
797     } else { /* I-Frame */
798         do{
799             cbpc = get_vlc2(&s->gb, ff_h263_intra_MCBPC_vlc.table, INTRA_MCBPC_VLC_BITS, 2);
800             if (cbpc < 0){
801                 av_log(s->avctx, AV_LOG_ERROR, "I cbpc damaged at %d %d\n", s->mb_x, s->mb_y);
802                 return -1;
803             }
804         }while(cbpc == 8);
805
806         s->bdsp.clear_blocks(s->block[0]);
807
808         dquant = cbpc & 4;
809         s->mb_intra = 1;
810 intra:
811         s->current_picture.mb_type[xy] = MB_TYPE_INTRA;
812         if (s->h263_aic) {
813             s->ac_pred = get_bits1(&s->gb);
814             if(s->ac_pred){
815                 s->current_picture.mb_type[xy] = MB_TYPE_INTRA | MB_TYPE_ACPRED;
816
817                 s->h263_aic_dir = get_bits1(&s->gb);
818             }
819         }else
820             s->ac_pred = 0;
821
822         if(s->pb_frame && get_bits1(&s->gb))
823             pb_mv_count = h263_get_modb(&s->gb, s->pb_frame, &cbpb);
824         cbpy = get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
825         if(cbpy<0){
826             av_log(s->avctx, AV_LOG_ERROR, "I cbpy damaged at %d %d\n", s->mb_x, s->mb_y);
827             return -1;
828         }
829         cbp = (cbpc & 3) | (cbpy << 2);
830         if (dquant) {
831             h263_decode_dquant(s);
832         }
833
834         pb_mv_count += !!s->pb_frame;
835     }
836
837     while(pb_mv_count--){
838         ff_h263_decode_motion(s, 0, 1);
839         ff_h263_decode_motion(s, 0, 1);
840     }
841
842     /* decode each block */
843     for (i = 0; i < 6; i++) {
844         if (h263_decode_block(s, block[i], i, cbp&32) < 0)
845             return -1;
846         cbp+=cbp;
847     }
848
849     if(s->pb_frame && h263_skip_b_part(s, cbpb) < 0)
850         return -1;
851     if(s->obmc && !s->mb_intra){
852         if(s->pict_type == AV_PICTURE_TYPE_P && s->mb_x+1<s->mb_width && s->mb_num_left != 1)
853             preview_obmc(s);
854     }
855 end:
856
857         /* per-MB end of slice check */
858     {
859         int v= show_bits(&s->gb, 16);
860
861         if (get_bits_left(&s->gb) < 16) {
862             v >>= 16 - get_bits_left(&s->gb);
863         }
864
865         if(v==0)
866             return SLICE_END;
867     }
868
869     return SLICE_OK;
870 }
871
872 /* most is hardcoded. should extend to handle all h263 streams */
873 int ff_h263_decode_picture_header(MpegEncContext *s)
874 {
875     int format, width, height, i;
876     uint32_t startcode;
877
878     align_get_bits(&s->gb);
879
880     if (show_bits(&s->gb, 2) == 2 && s->avctx->frame_number == 0) {
881          av_log(s->avctx, AV_LOG_WARNING, "Header looks like RTP instead of H.263\n");
882     }
883
884     startcode= get_bits(&s->gb, 22-8);
885
886     for(i= get_bits_left(&s->gb); i>24; i-=8) {
887         startcode = ((startcode << 8) | get_bits(&s->gb, 8)) & 0x003FFFFF;
888
889         if(startcode == 0x20)
890             break;
891     }
892
893     if (startcode != 0x20) {
894         av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
895         return -1;
896     }
897     /* temporal reference */
898     i = get_bits(&s->gb, 8); /* picture timestamp */
899     if( (s->picture_number&~0xFF)+i < s->picture_number)
900         i+= 256;
901     s->picture_number= (s->picture_number&~0xFF) + i;
902
903     /* PTYPE starts here */
904     if (get_bits1(&s->gb) != 1) {
905         /* marker */
906         av_log(s->avctx, AV_LOG_ERROR, "Bad marker\n");
907         return -1;
908     }
909     if (get_bits1(&s->gb) != 0) {
910         av_log(s->avctx, AV_LOG_ERROR, "Bad H263 id\n");
911         return -1;      /* h263 id */
912     }
913     skip_bits1(&s->gb);         /* split screen off */
914     skip_bits1(&s->gb);         /* camera  off */
915     skip_bits1(&s->gb);         /* freeze picture release off */
916
917     format = get_bits(&s->gb, 3);
918     /*
919         0    forbidden
920         1    sub-QCIF
921         10   QCIF
922         7       extended PTYPE (PLUSPTYPE)
923     */
924
925     if (format != 7 && format != 6) {
926         s->h263_plus = 0;
927         /* H.263v1 */
928         width = ff_h263_format[format][0];
929         height = ff_h263_format[format][1];
930         if (!width)
931             return -1;
932
933         s->pict_type = AV_PICTURE_TYPE_I + get_bits1(&s->gb);
934
935         s->h263_long_vectors = get_bits1(&s->gb);
936
937         if (get_bits1(&s->gb) != 0) {
938             av_log(s->avctx, AV_LOG_ERROR, "H263 SAC not supported\n");
939             return -1; /* SAC: off */
940         }
941         s->obmc= get_bits1(&s->gb); /* Advanced prediction mode */
942         s->unrestricted_mv = s->h263_long_vectors || s->obmc;
943
944         s->pb_frame = get_bits1(&s->gb);
945         s->chroma_qscale= s->qscale = get_bits(&s->gb, 5);
946         skip_bits1(&s->gb); /* Continuous Presence Multipoint mode: off */
947
948         s->width = width;
949         s->height = height;
950         s->avctx->sample_aspect_ratio= (AVRational){12,11};
951         s->avctx->time_base= (AVRational){1001, 30000};
952     } else {
953         int ufep;
954
955         /* H.263v2 */
956         s->h263_plus = 1;
957         ufep = get_bits(&s->gb, 3); /* Update Full Extended PTYPE */
958
959         /* ufep other than 0 and 1 are reserved */
960         if (ufep == 1) {
961             /* OPPTYPE */
962             format = get_bits(&s->gb, 3);
963             av_dlog(s->avctx, "ufep=1, format: %d\n", format);
964             s->custom_pcf= get_bits1(&s->gb);
965             s->umvplus = get_bits1(&s->gb); /* Unrestricted Motion Vector */
966             if (get_bits1(&s->gb) != 0) {
967                 av_log(s->avctx, AV_LOG_ERROR, "Syntax-based Arithmetic Coding (SAC) not supported\n");
968             }
969             s->obmc= get_bits1(&s->gb); /* Advanced prediction mode */
970             s->h263_aic = get_bits1(&s->gb); /* Advanced Intra Coding (AIC) */
971             s->loop_filter= get_bits1(&s->gb);
972             s->unrestricted_mv = s->umvplus || s->obmc || s->loop_filter;
973             if(s->avctx->lowres)
974                 s->loop_filter = 0;
975
976             s->h263_slice_structured= get_bits1(&s->gb);
977             if (get_bits1(&s->gb) != 0) {
978                 av_log(s->avctx, AV_LOG_ERROR, "Reference Picture Selection not supported\n");
979             }
980             if (get_bits1(&s->gb) != 0) {
981                 av_log(s->avctx, AV_LOG_ERROR, "Independent Segment Decoding not supported\n");
982             }
983             s->alt_inter_vlc= get_bits1(&s->gb);
984             s->modified_quant= get_bits1(&s->gb);
985             if(s->modified_quant)
986                 s->chroma_qscale_table= ff_h263_chroma_qscale_table;
987
988             skip_bits(&s->gb, 1); /* Prevent start code emulation */
989
990             skip_bits(&s->gb, 3); /* Reserved */
991         } else if (ufep != 0) {
992             av_log(s->avctx, AV_LOG_ERROR, "Bad UFEP type (%d)\n", ufep);
993             return -1;
994         }
995
996         /* MPPTYPE */
997         s->pict_type = get_bits(&s->gb, 3);
998         switch(s->pict_type){
999         case 0: s->pict_type= AV_PICTURE_TYPE_I;break;
1000         case 1: s->pict_type= AV_PICTURE_TYPE_P;break;
1001         case 2: s->pict_type= AV_PICTURE_TYPE_P;s->pb_frame = 3;break;
1002         case 3: s->pict_type= AV_PICTURE_TYPE_B;break;
1003         case 7: s->pict_type= AV_PICTURE_TYPE_I;break; //ZYGO
1004         default:
1005             return -1;
1006         }
1007         skip_bits(&s->gb, 2);
1008         s->no_rounding = get_bits1(&s->gb);
1009         skip_bits(&s->gb, 4);
1010
1011         /* Get the picture dimensions */
1012         if (ufep) {
1013             if (format == 6) {
1014                 /* Custom Picture Format (CPFMT) */
1015                 s->aspect_ratio_info = get_bits(&s->gb, 4);
1016                 av_dlog(s->avctx, "aspect: %d\n", s->aspect_ratio_info);
1017                 /* aspect ratios:
1018                 0 - forbidden
1019                 1 - 1:1
1020                 2 - 12:11 (CIF 4:3)
1021                 3 - 10:11 (525-type 4:3)
1022                 4 - 16:11 (CIF 16:9)
1023                 5 - 40:33 (525-type 16:9)
1024                 6-14 - reserved
1025                 */
1026                 width = (get_bits(&s->gb, 9) + 1) * 4;
1027                 skip_bits1(&s->gb);
1028                 height = get_bits(&s->gb, 9) * 4;
1029                 av_dlog(s->avctx, "\nH.263+ Custom picture: %dx%d\n",width,height);
1030                 if (s->aspect_ratio_info == FF_ASPECT_EXTENDED) {
1031                     /* aspected dimensions */
1032                     s->avctx->sample_aspect_ratio.num= get_bits(&s->gb, 8);
1033                     s->avctx->sample_aspect_ratio.den= get_bits(&s->gb, 8);
1034                 }else{
1035                     s->avctx->sample_aspect_ratio= ff_h263_pixel_aspect[s->aspect_ratio_info];
1036                 }
1037             } else {
1038                 width = ff_h263_format[format][0];
1039                 height = ff_h263_format[format][1];
1040                 s->avctx->sample_aspect_ratio= (AVRational){12,11};
1041             }
1042             s->avctx->sample_aspect_ratio.den <<= s->ehc_mode;
1043             if ((width == 0) || (height == 0))
1044                 return -1;
1045             s->width = width;
1046             s->height = height;
1047
1048             if(s->custom_pcf){
1049                 int gcd;
1050                 s->avctx->time_base.den= 1800000;
1051                 s->avctx->time_base.num= 1000 + get_bits1(&s->gb);
1052                 s->avctx->time_base.num*= get_bits(&s->gb, 7);
1053                 if(s->avctx->time_base.num == 0){
1054                     av_log(s, AV_LOG_ERROR, "zero framerate\n");
1055                     return -1;
1056                 }
1057                 gcd= av_gcd(s->avctx->time_base.den, s->avctx->time_base.num);
1058                 s->avctx->time_base.den /= gcd;
1059                 s->avctx->time_base.num /= gcd;
1060             }else{
1061                 s->avctx->time_base= (AVRational){1001, 30000};
1062             }
1063         }
1064
1065         if(s->custom_pcf){
1066             skip_bits(&s->gb, 2); //extended Temporal reference
1067         }
1068
1069         if (ufep) {
1070             if (s->umvplus) {
1071                 if(get_bits1(&s->gb)==0) /* Unlimited Unrestricted Motion Vectors Indicator (UUI) */
1072                     skip_bits1(&s->gb);
1073             }
1074             if(s->h263_slice_structured){
1075                 if (get_bits1(&s->gb) != 0) {
1076                     av_log(s->avctx, AV_LOG_ERROR, "rectangular slices not supported\n");
1077                 }
1078                 if (get_bits1(&s->gb) != 0) {
1079                     av_log(s->avctx, AV_LOG_ERROR, "unordered slices not supported\n");
1080                 }
1081             }
1082         }
1083
1084         s->qscale = get_bits(&s->gb, 5);
1085     }
1086
1087     if (s->width == 0 || s->height == 0) {
1088         av_log(s->avctx, AV_LOG_ERROR, "dimensions 0\n");
1089         return -1;
1090     }
1091     s->mb_width = (s->width  + 15) / 16;
1092     s->mb_height = (s->height  + 15) / 16;
1093     s->mb_num = s->mb_width * s->mb_height;
1094
1095     if (s->pb_frame) {
1096         skip_bits(&s->gb, 3); /* Temporal reference for B-pictures */
1097         if (s->custom_pcf)
1098             skip_bits(&s->gb, 2); //extended Temporal reference
1099         skip_bits(&s->gb, 2); /* Quantization information for B-pictures */
1100     }
1101
1102     if (s->pict_type!=AV_PICTURE_TYPE_B) {
1103         s->time            = s->picture_number;
1104         s->pp_time         = s->time - s->last_non_b_time;
1105         s->last_non_b_time = s->time;
1106     }else{
1107         s->time    = s->picture_number;
1108         s->pb_time = s->pp_time - (s->last_non_b_time - s->time);
1109         if (s->pp_time <=s->pb_time ||
1110             s->pp_time <= s->pp_time - s->pb_time ||
1111             s->pp_time <= 0){
1112             s->pp_time = 2;
1113             s->pb_time = 1;
1114         }
1115         ff_mpeg4_init_direct_mv(s);
1116     }
1117
1118     /* PEI */
1119     if (skip_1stop_8data_bits(&s->gb) < 0)
1120         return AVERROR_INVALIDDATA;
1121
1122     if(s->h263_slice_structured){
1123         if (get_bits1(&s->gb) != 1) {
1124             av_log(s->avctx, AV_LOG_ERROR, "SEPB1 marker missing\n");
1125             return -1;
1126         }
1127
1128         ff_h263_decode_mba(s);
1129
1130         if (get_bits1(&s->gb) != 1) {
1131             av_log(s->avctx, AV_LOG_ERROR, "SEPB2 marker missing\n");
1132             return -1;
1133         }
1134     }
1135     s->f_code = 1;
1136
1137     if(s->h263_aic){
1138          s->y_dc_scale_table=
1139          s->c_dc_scale_table= ff_aic_dc_scale_table;
1140     }else{
1141         s->y_dc_scale_table=
1142         s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
1143     }
1144
1145         ff_h263_show_pict_info(s);
1146     if (s->pict_type == AV_PICTURE_TYPE_I && s->codec_tag == AV_RL32("ZYGO") && get_bits_left(&s->gb) >= 85 + 13*3*16 + 50){
1147         int i,j;
1148         for(i=0; i<85; i++) av_log(s->avctx, AV_LOG_DEBUG, "%d", get_bits1(&s->gb));
1149         av_log(s->avctx, AV_LOG_DEBUG, "\n");
1150         for(i=0; i<13; i++){
1151             for(j=0; j<3; j++){
1152                 int v= get_bits(&s->gb, 8);
1153                 v |= get_sbits(&s->gb, 8)<<8;
1154                 av_log(s->avctx, AV_LOG_DEBUG, " %5d", v);
1155             }
1156             av_log(s->avctx, AV_LOG_DEBUG, "\n");
1157         }
1158         for(i=0; i<50; i++) av_log(s->avctx, AV_LOG_DEBUG, "%d", get_bits1(&s->gb));
1159     }
1160
1161     return 0;
1162 }