042e683f90bf63ab16342e48f1cbc8830f9ce6be
[libav.git] / libavcodec / h261.c
1 /*
2 * H261 decoder
3 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
4 * Copyright (c) 2004 Maarten Daniels
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 /**
24 * @file h261.c
25 * h261codec.
26 */
27
28 #include "dsputil.h"
29 #include "avcodec.h"
30 #include "mpegvideo.h"
31 #include "h261data.h"
32
33
34 #define H261_MBA_VLC_BITS 9
35 #define H261_MTYPE_VLC_BITS 6
36 #define H261_MV_VLC_BITS 7
37 #define H261_CBP_VLC_BITS 9
38 #define TCOEFF_VLC_BITS 9
39
40 #define MBA_STUFFING 33
41 #define MBA_STARTCODE 34
42 #define IS_FIL(a) ((a)&MB_TYPE_H261_FIL)
43
44 /**
45 * H261Context
46 */
47 typedef struct H261Context{
48 MpegEncContext s;
49
50 int current_mba;
51 int previous_mba;
52 int mba_diff;
53 int mtype;
54 int current_mv_x;
55 int current_mv_y;
56 int gob_number;
57 int gob_start_code_skipped; // 1 if gob start code is already read before gob header is read
58 }H261Context;
59
60 static uint8_t static_rl_table_store[2][2*MAX_RUN + MAX_LEVEL + 3];
61
62 void ff_h261_loop_filter(MpegEncContext *s){
63 H261Context * h= (H261Context*)s;
64 const int linesize = s->linesize;
65 const int uvlinesize= s->uvlinesize;
66 uint8_t *dest_y = s->dest[0];
67 uint8_t *dest_cb= s->dest[1];
68 uint8_t *dest_cr= s->dest[2];
69
70 if(!(IS_FIL (h->mtype)))
71 return;
72
73 s->dsp.h261_loop_filter(dest_y , linesize);
74 s->dsp.h261_loop_filter(dest_y + 8, linesize);
75 s->dsp.h261_loop_filter(dest_y + 8 * linesize , linesize);
76 s->dsp.h261_loop_filter(dest_y + 8 * linesize + 8, linesize);
77 s->dsp.h261_loop_filter(dest_cb, uvlinesize);
78 s->dsp.h261_loop_filter(dest_cr, uvlinesize);
79 }
80
81 int ff_h261_get_picture_format(int width, int height){
82 // QCIF
83 if (width == 176 && height == 144)
84 return 0;
85 // CIF
86 else if (width == 352 && height == 288)
87 return 1;
88 // ERROR
89 else
90 return -1;
91 }
92
93 static void h261_encode_block(H261Context * h, DCTELEM * block,
94 int n);
95 static int h261_decode_block(H261Context *h, DCTELEM *block,
96 int n, int coded);
97
98 void ff_h261_encode_picture_header(MpegEncContext * s, int picture_number){
99 H261Context * h = (H261Context *) s;
100 int format, temp_ref;
101
102 align_put_bits(&s->pb);
103
104 /* Update the pointer to last GOB */
105 s->ptr_lastgob = pbBufPtr(&s->pb);
106
107 put_bits(&s->pb, 20, 0x10); /* PSC */
108
109 temp_ref= s->picture_number * (int64_t)30000 * s->avctx->time_base.num /
110 (1001 * (int64_t)s->avctx->time_base.den); //FIXME maybe this should use a timestamp
111 put_bits(&s->pb, 5, temp_ref & 0x1f); /* TemporalReference */
112
113 put_bits(&s->pb, 1, 0); /* split screen off */
114 put_bits(&s->pb, 1, 0); /* camera off */
115 put_bits(&s->pb, 1, 0); /* freeze picture release off */
116
117 format = ff_h261_get_picture_format(s->width, s->height);
118
119 put_bits(&s->pb, 1, format); /* 0 == QCIF, 1 == CIF */
120
121 put_bits(&s->pb, 1, 0); /* still image mode */
122 put_bits(&s->pb, 1, 0); /* reserved */
123
124 put_bits(&s->pb, 1, 0); /* no PEI */
125 if(format == 0)
126 h->gob_number = -1;
127 else
128 h->gob_number = 0;
129 h->current_mba = 0;
130 }
131
132 /**
133 * Encodes a group of blocks header.
134 */
135 static void h261_encode_gob_header(MpegEncContext * s, int mb_line){
136 H261Context * h = (H261Context *)s;
137 if(ff_h261_get_picture_format(s->width, s->height) == 0){
138 h->gob_number+=2; // QCIF
139 }
140 else{
141 h->gob_number++; // CIF
142 }
143 put_bits(&s->pb, 16, 1); /* GBSC */
144 put_bits(&s->pb, 4, h->gob_number); /* GN */
145 put_bits(&s->pb, 5, s->qscale); /* GQUANT */
146 put_bits(&s->pb, 1, 0); /* no GEI */
147 h->current_mba = 0;
148 h->previous_mba = 0;
149 h->current_mv_x=0;
150 h->current_mv_y=0;
151 }
152
153 void ff_h261_reorder_mb_index(MpegEncContext* s){
154 int index= s->mb_x + s->mb_y*s->mb_width;
155
156 if(index % 33 == 0)
157 h261_encode_gob_header(s,0);
158
159 /* for CIF the GOB's are fragmented in the middle of a scanline
160 that's why we need to adjust the x and y index of the macroblocks */
161 if(ff_h261_get_picture_format(s->width,s->height) == 1){ // CIF
162 s->mb_x = index % 11 ; index /= 11;
163 s->mb_y = index % 3 ; index /= 3;
164 s->mb_x+= 11*(index % 2); index /= 2;
165 s->mb_y+= 3*index;
166
167 ff_init_block_index(s);
168 ff_update_block_index(s);
169 }
170 }
171
172 static void h261_encode_motion(H261Context * h, int val){
173 MpegEncContext * const s = &h->s;
174 int sign, code;
175 if(val==0){
176 code = 0;
177 put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
178 }
179 else{
180 if(val > 15)
181 val -=32;
182 if(val < -16)
183 val+=32;
184 sign = val < 0;
185 code = sign ? -val : val;
186 put_bits(&s->pb,h261_mv_tab[code][1],h261_mv_tab[code][0]);
187 put_bits(&s->pb,1,sign);
188 }
189 }
190
191 static inline int get_cbp(MpegEncContext * s,
192 DCTELEM block[6][64])
193 {
194 int i, cbp;
195 cbp= 0;
196 for (i = 0; i < 6; i++) {
197 if (s->block_last_index[i] >= 0)
198 cbp |= 1 << (5 - i);
199 }
200 return cbp;
201 }
202 void ff_h261_encode_mb(MpegEncContext * s,
203 DCTELEM block[6][64],
204 int motion_x, int motion_y)
205 {
206 H261Context * h = (H261Context *)s;
207 int mvd, mv_diff_x, mv_diff_y, i, cbp;
208 cbp = 63; // avoid warning
209 mvd = 0;
210
211 h->current_mba++;
212 h->mtype = 0;
213
214 if (!s->mb_intra){
215 /* compute cbp */
216 cbp= get_cbp(s, block);
217
218 /* mvd indicates if this block is motion compensated */
219 mvd = motion_x | motion_y;
220
221 if((cbp | mvd | s->dquant ) == 0) {
222 /* skip macroblock */
223 s->skip_count++;
224 h->current_mv_x=0;
225 h->current_mv_y=0;
226 return;
227 }
228 }
229
230 /* MB is not skipped, encode MBA */
231 put_bits(&s->pb, h261_mba_bits[(h->current_mba-h->previous_mba)-1], h261_mba_code[(h->current_mba-h->previous_mba)-1]);
232
233 /* calculate MTYPE */
234 if(!s->mb_intra){
235 h->mtype++;
236
237 if(mvd || s->loop_filter)
238 h->mtype+=3;
239 if(s->loop_filter)
240 h->mtype+=3;
241 if(cbp || s->dquant)
242 h->mtype++;
243 assert(h->mtype > 1);
244 }
245
246 if(s->dquant)
247 h->mtype++;
248
249 put_bits(&s->pb, h261_mtype_bits[h->mtype], h261_mtype_code[h->mtype]);
250
251 h->mtype = h261_mtype_map[h->mtype];
252
253 if(IS_QUANT(h->mtype)){
254 ff_set_qscale(s,s->qscale+s->dquant);
255 put_bits(&s->pb, 5, s->qscale);
256 }
257
258 if(IS_16X16(h->mtype)){
259 mv_diff_x = (motion_x >> 1) - h->current_mv_x;
260 mv_diff_y = (motion_y >> 1) - h->current_mv_y;
261 h->current_mv_x = (motion_x >> 1);
262 h->current_mv_y = (motion_y >> 1);
263 h261_encode_motion(h,mv_diff_x);
264 h261_encode_motion(h,mv_diff_y);
265 }
266
267 h->previous_mba = h->current_mba;
268
269 if(HAS_CBP(h->mtype)){
270 assert(cbp>0);
271 put_bits(&s->pb,h261_cbp_tab[cbp-1][1],h261_cbp_tab[cbp-1][0]);
272 }
273 for(i=0; i<6; i++) {
274 /* encode each block */
275 h261_encode_block(h, block[i], i);
276 }
277
278 if ( ( h->current_mba == 11 ) || ( h->current_mba == 22 ) || ( h->current_mba == 33 ) || ( !IS_16X16 ( h->mtype ) )){
279 h->current_mv_x=0;
280 h->current_mv_y=0;
281 }
282 }
283
284 void ff_h261_encode_init(MpegEncContext *s){
285 static int done = 0;
286
287 if (!done) {
288 done = 1;
289 init_rl(&h261_rl_tcoeff, static_rl_table_store);
290 }
291
292 s->min_qcoeff= -127;
293 s->max_qcoeff= 127;
294 s->y_dc_scale_table=
295 s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
296 }
297
298
299 /**
300 * encodes a 8x8 block.
301 * @param block the 8x8 block
302 * @param n block index (0-3 are luma, 4-5 are chroma)
303 */
304 static void h261_encode_block(H261Context * h, DCTELEM * block, int n){
305 MpegEncContext * const s = &h->s;
306 int level, run, last, i, j, last_index, last_non_zero, sign, slevel, code;
307 RLTable *rl;
308
309 rl = &h261_rl_tcoeff;
310 if (s->mb_intra) {
311 /* DC coef */
312 level = block[0];
313 /* 255 cannot be represented, so we clamp */
314 if (level > 254) {
315 level = 254;
316 block[0] = 254;
317 }
318 /* 0 cannot be represented also */
319 else if (level < 1) {
320 level = 1;
321 block[0] = 1;
322 }
323 if (level == 128)
324 put_bits(&s->pb, 8, 0xff);
325 else
326 put_bits(&s->pb, 8, level);
327 i = 1;
328 } else if((block[0]==1 || block[0] == -1) && (s->block_last_index[n] > -1)){
329 //special case
330 put_bits(&s->pb,2,block[0]>0 ? 2 : 3 );
331 i = 1;
332 } else {
333 i = 0;
334 }
335
336 /* AC coefs */
337 last_index = s->block_last_index[n];
338 last_non_zero = i - 1;
339 for (; i <= last_index; i++) {
340 j = s->intra_scantable.permutated[i];
341 level = block[j];
342 if (level) {
343 run = i - last_non_zero - 1;
344 last = (i == last_index);
345 sign = 0;
346 slevel = level;
347 if (level < 0) {
348 sign = 1;
349 level = -level;
350 }
351 code = get_rl_index(rl, 0 /*no last in H.261, EOB is used*/, run, level);
352 if(run==0 && level < 16)
353 code+=1;
354 put_bits(&s->pb, rl->table_vlc[code][1], rl->table_vlc[code][0]);
355 if (code == rl->n) {
356 put_bits(&s->pb, 6, run);
357 assert(slevel != 0);
358 assert(level <= 127);
359 put_bits(&s->pb, 8, slevel & 0xff);
360 } else {
361 put_bits(&s->pb, 1, sign);
362 }
363 last_non_zero = i;
364 }
365 }
366 if(last_index > -1){
367 put_bits(&s->pb, rl->table_vlc[0][1], rl->table_vlc[0][0]);// END OF BLOCK
368 }
369 }
370
371 /***********************************************/
372 /* decoding */
373
374 static VLC h261_mba_vlc;
375 static VLC h261_mtype_vlc;
376 static VLC h261_mv_vlc;
377 static VLC h261_cbp_vlc;
378
379 static void h261_decode_init_vlc(H261Context *h){
380 static int done = 0;
381
382 if(!done){
383 done = 1;
384 init_vlc(&h261_mba_vlc, H261_MBA_VLC_BITS, 35,
385 h261_mba_bits, 1, 1,
386 h261_mba_code, 1, 1, 1);
387 init_vlc(&h261_mtype_vlc, H261_MTYPE_VLC_BITS, 10,
388 h261_mtype_bits, 1, 1,
389 h261_mtype_code, 1, 1, 1);
390 init_vlc(&h261_mv_vlc, H261_MV_VLC_BITS, 17,
391 &h261_mv_tab[0][1], 2, 1,
392 &h261_mv_tab[0][0], 2, 1, 1);
393 init_vlc(&h261_cbp_vlc, H261_CBP_VLC_BITS, 63,
394 &h261_cbp_tab[0][1], 2, 1,
395 &h261_cbp_tab[0][0], 2, 1, 1);
396 init_rl(&h261_rl_tcoeff, static_rl_table_store);
397 init_vlc_rl(&h261_rl_tcoeff, 1);
398 }
399 }
400
401 static int h261_decode_init(AVCodecContext *avctx){
402 H261Context *h= avctx->priv_data;
403 MpegEncContext * const s = &h->s;
404
405 // set defaults
406 MPV_decode_defaults(s);
407 s->avctx = avctx;
408
409 s->width = s->avctx->coded_width;
410 s->height = s->avctx->coded_height;
411 s->codec_id = s->avctx->codec->id;
412
413 s->out_format = FMT_H261;
414 s->low_delay= 1;
415 avctx->pix_fmt= PIX_FMT_YUV420P;
416
417 s->codec_id= avctx->codec->id;
418
419 h261_decode_init_vlc(h);
420
421 h->gob_start_code_skipped = 0;
422
423 return 0;
424 }
425
426 /**
427 * decodes the group of blocks header or slice header.
428 * @return <0 if an error occured
429 */
430 static int h261_decode_gob_header(H261Context *h){
431 unsigned int val;
432 MpegEncContext * const s = &h->s;
433
434 if ( !h->gob_start_code_skipped ){
435 /* Check for GOB Start Code */
436 val = show_bits(&s->gb, 15);
437 if(val)
438 return -1;
439
440 /* We have a GBSC */
441 skip_bits(&s->gb, 16);
442 }
443
444 h->gob_start_code_skipped = 0;
445
446 h->gob_number = get_bits(&s->gb, 4); /* GN */
447 s->qscale = get_bits(&s->gb, 5); /* GQUANT */
448
449 /* Check if gob_number is valid */
450 if (s->mb_height==18){ //cif
451 if ((h->gob_number<=0) || (h->gob_number>12))
452 return -1;
453 }
454 else{ //qcif
455 if ((h->gob_number!=1) && (h->gob_number!=3) && (h->gob_number!=5))
456 return -1;
457 }
458
459 /* GEI */
460 while (get_bits1(&s->gb) != 0) {
461 skip_bits(&s->gb, 8);
462 }
463
464 if(s->qscale==0)
465 return -1;
466
467 // For the first transmitted macroblock in a GOB, MBA is the absolute address. For
468 // subsequent macroblocks, MBA is the difference between the absolute addresses of
469 // the macroblock and the last transmitted macroblock.
470 h->current_mba = 0;
471 h->mba_diff = 0;
472
473 return 0;
474 }
475
476 /**
477 * decodes the group of blocks / video packet header.
478 * @return <0 if no resync found
479 */
480 static int ff_h261_resync(H261Context *h){
481 MpegEncContext * const s = &h->s;
482 int left, ret;
483
484 if ( h->gob_start_code_skipped ){
485 ret= h261_decode_gob_header(h);
486 if(ret>=0)
487 return 0;
488 }
489 else{
490 if(show_bits(&s->gb, 15)==0){
491 ret= h261_decode_gob_header(h);
492 if(ret>=0)
493 return 0;
494 }
495 //ok, its not where its supposed to be ...
496 s->gb= s->last_resync_gb;
497 align_get_bits(&s->gb);
498 left= s->gb.size_in_bits - get_bits_count(&s->gb);
499
500 for(;left>15+1+4+5; left-=8){
501 if(show_bits(&s->gb, 15)==0){
502 GetBitContext bak= s->gb;
503
504 ret= h261_decode_gob_header(h);
505 if(ret>=0)
506 return 0;
507
508 s->gb= bak;
509 }
510 skip_bits(&s->gb, 8);
511 }
512 }
513
514 return -1;
515 }
516
517 /**
518 * decodes skipped macroblocks
519 * @return 0
520 */
521 static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2 )
522 {
523 MpegEncContext * const s = &h->s;
524 int i;
525
526 s->mb_intra = 0;
527
528 for(i=mba1; i<mba2; i++){
529 int j, xy;
530
531 s->mb_x= ((h->gob_number-1) % 2) * 11 + i % 11;
532 s->mb_y= ((h->gob_number-1) / 2) * 3 + i / 11;
533 xy = s->mb_x + s->mb_y * s->mb_stride;
534 ff_init_block_index(s);
535 ff_update_block_index(s);
536
537 for(j=0;j<6;j++)
538 s->block_last_index[j] = -1;
539
540 s->mv_dir = MV_DIR_FORWARD;
541 s->mv_type = MV_TYPE_16X16;
542 s->current_picture.mb_type[xy]= MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
543 s->mv[0][0][0] = 0;
544 s->mv[0][0][1] = 0;
545 s->mb_skipped = 1;
546 h->mtype &= ~MB_TYPE_H261_FIL;
547
548 MPV_decode_mb(s, s->block);
549 }
550
551 return 0;
552 }
553
554 static int decode_mv_component(GetBitContext *gb, int v){
555 int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
556
557 /* check if mv_diff is valid */
558 if ( mv_diff < 0 )
559 return v;
560
561 mv_diff = mvmap[mv_diff];
562
563 if(mv_diff && !get_bits1(gb))
564 mv_diff= -mv_diff;
565
566 v += mv_diff;
567 if (v <=-16) v+= 32;
568 else if(v >= 16) v-= 32;
569
570 return v;
571 }
572
573 static int h261_decode_mb(H261Context *h){
574 MpegEncContext * const s = &h->s;
575 int i, cbp, xy;
576
577 cbp = 63;
578 // Read mba
579 do{
580 h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2);
581
582 /* Check for slice end */
583 /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
584 if (h->mba_diff == MBA_STARTCODE){ // start code
585 h->gob_start_code_skipped = 1;
586 return SLICE_END;
587 }
588 }
589 while( h->mba_diff == MBA_STUFFING ); // stuffing
590
591 if ( h->mba_diff < 0 ){
592 if ( get_bits_count(&s->gb) + 7 >= s->gb.size_in_bits )
593 return SLICE_END;
594
595 av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
596 return SLICE_ERROR;
597 }
598
599 h->mba_diff += 1;
600 h->current_mba += h->mba_diff;
601
602 if ( h->current_mba > MBA_STUFFING )
603 return SLICE_ERROR;
604
605 s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11);
606 s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11);
607 xy = s->mb_x + s->mb_y * s->mb_stride;
608 ff_init_block_index(s);
609 ff_update_block_index(s);
610
611 // Read mtype
612 h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
613 h->mtype = h261_mtype_map[h->mtype];
614
615 // Read mquant
616 if ( IS_QUANT ( h->mtype ) ){
617 ff_set_qscale(s, get_bits(&s->gb, 5));
618 }
619
620 s->mb_intra = IS_INTRA4x4(h->mtype);
621
622 // Read mv
623 if ( IS_16X16 ( h->mtype ) ){
624 // Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the
625 // vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the
626 // following three situations:
627 // 1) evaluating MVD for macroblocks 1, 12 and 23;
628 // 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
629 // 3) MTYPE of the previous macroblock was not MC.
630 if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) ||
631 ( h->mba_diff != 1))
632 {
633 h->current_mv_x = 0;
634 h->current_mv_y = 0;
635 }
636
637 h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x);
638 h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y);
639 }else{
640 h->current_mv_x = 0;
641 h->current_mv_y = 0;
642 }
643
644 // Read cbp
645 if ( HAS_CBP( h->mtype ) ){
646 cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
647 }
648
649 if(s->mb_intra){
650 s->current_picture.mb_type[xy]= MB_TYPE_INTRA;
651 goto intra;
652 }
653
654 //set motion vectors
655 s->mv_dir = MV_DIR_FORWARD;
656 s->mv_type = MV_TYPE_16X16;
657 s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0;
658 s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation
659 s->mv[0][0][1] = h->current_mv_y * 2;
660
661 intra:
662 /* decode each block */
663 if(s->mb_intra || HAS_CBP(h->mtype)){
664 s->dsp.clear_blocks(s->block[0]);
665 for (i = 0; i < 6; i++) {
666 if (h261_decode_block(h, s->block[i], i, cbp&32) < 0){
667 return SLICE_ERROR;
668 }
669 cbp+=cbp;
670 }
671 }else{
672 for (i = 0; i < 6; i++)
673 s->block_last_index[i]= -1;
674 }
675
676 MPV_decode_mb(s, s->block);
677
678 return SLICE_OK;
679 }
680
681 /**
682 * decodes a macroblock
683 * @return <0 if an error occured
684 */
685 static int h261_decode_block(H261Context * h, DCTELEM * block,
686 int n, int coded)
687 {
688 MpegEncContext * const s = &h->s;
689 int code, level, i, j, run;
690 RLTable *rl = &h261_rl_tcoeff;
691 const uint8_t *scan_table;
692
693 // For the variable length encoding there are two code tables, one being used for
694 // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
695 // for all other LEVELs except the first one in INTRA blocks which is fixed length
696 // coded with 8 bits.
697 // NOTE: the two code tables only differ in one VLC so we handle that manually.
698 scan_table = s->intra_scantable.permutated;
699 if (s->mb_intra){
700 /* DC coef */
701 level = get_bits(&s->gb, 8);
702 // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
703 if((level&0x7F) == 0){
704 av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
705 return -1;
706 }
707 // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
708 if (level == 255)
709 level = 128;
710 block[0] = level;
711 i = 1;
712 }else if(coded){
713 // Run Level Code
714 // EOB Not possible for first level when cbp is available (that's why the table is different)
715 // 0 1 1s
716 // * * 0*
717 int check = show_bits(&s->gb, 2);
718 i = 0;
719 if ( check & 0x2 ){
720 skip_bits(&s->gb, 2);
721 block[0] = ( check & 0x1 ) ? -1 : 1;
722 i = 1;
723 }
724 }else{
725 i = 0;
726 }
727 if(!coded){
728 s->block_last_index[n] = i - 1;
729 return 0;
730 }
731 for(;;){
732 code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
733 if (code < 0){
734 av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
735 return -1;
736 }
737 if (code == rl->n) {
738 /* escape */
739 // The remaining combinations of (run, level) are encoded with a 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits level.
740 run = get_bits(&s->gb, 6);
741 level = get_sbits(&s->gb, 8);
742 }else if(code == 0){
743 break;
744 }else{
745 run = rl->table_run[code];
746 level = rl->table_level[code];
747 if (get_bits1(&s->gb))
748 level = -level;
749 }
750 i += run;
751 if (i >= 64){
752 av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
753 return -1;
754 }
755 j = scan_table[i];
756 block[j] = level;
757 i++;
758 }
759 s->block_last_index[n] = i-1;
760 return 0;
761 }
762
763 /**
764 * decodes the H261 picture header.
765 * @return <0 if no startcode found
766 */
767 static int h261_decode_picture_header(H261Context *h){
768 MpegEncContext * const s = &h->s;
769 int format, i;
770 uint32_t startcode= 0;
771
772 for(i= s->gb.size_in_bits - get_bits_count(&s->gb); i>24; i-=1){
773 startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
774
775 if(startcode == 0x10)
776 break;
777 }
778
779 if (startcode != 0x10){
780 av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
781 return -1;
782 }
783
784 /* temporal reference */
785 i= get_bits(&s->gb, 5); /* picture timestamp */
786 if(i < (s->picture_number&31))
787 i += 32;
788 s->picture_number = (s->picture_number&~31) + i;
789
790 s->avctx->time_base= (AVRational){1001, 30000};
791 s->current_picture.pts= s->picture_number;
792
793
794 /* PTYPE starts here */
795 skip_bits1(&s->gb); /* split screen off */
796 skip_bits1(&s->gb); /* camera off */
797 skip_bits1(&s->gb); /* freeze picture release off */
798
799 format = get_bits1(&s->gb);
800
801 //only 2 formats possible
802 if (format == 0){//QCIF
803 s->width = 176;
804 s->height = 144;
805 s->mb_width = 11;
806 s->mb_height = 9;
807 }else{//CIF
808 s->width = 352;
809 s->height = 288;
810 s->mb_width = 22;
811 s->mb_height = 18;
812 }
813
814 s->mb_num = s->mb_width * s->mb_height;
815
816 skip_bits1(&s->gb); /* still image mode off */
817 skip_bits1(&s->gb); /* Reserved */
818
819 /* PEI */
820 while (get_bits1(&s->gb) != 0){
821 skip_bits(&s->gb, 8);
822 }
823
824 // h261 has no I-FRAMES, but if we pass I_TYPE for the first frame, the codec crashes if it does
825 // not contain all I-blocks (e.g. when a packet is lost)
826 s->pict_type = P_TYPE;
827
828 h->gob_number = 0;
829 return 0;
830 }
831
832 static int h261_decode_gob(H261Context *h){
833 MpegEncContext * const s = &h->s;
834
835 ff_set_qscale(s, s->qscale);
836
837 /* decode mb's */
838 while(h->current_mba <= MBA_STUFFING)
839 {
840 int ret;
841 /* DCT & quantize */
842 ret= h261_decode_mb(h);
843 if(ret<0){
844 if(ret==SLICE_END){
845 h261_decode_mb_skipped(h, h->current_mba, 33);
846 return 0;
847 }
848 av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n", s->mb_x + s->mb_y*s->mb_stride);
849 return -1;
850 }
851
852 h261_decode_mb_skipped(h, h->current_mba-h->mba_diff, h->current_mba-1);
853 }
854
855 return -1;
856 }
857
858 /**
859 * returns the number of bytes consumed for building the current frame
860 */
861 static int get_consumed_bytes(MpegEncContext *s, int buf_size){
862 int pos= get_bits_count(&s->gb)>>3;
863 if(pos==0) pos=1; //avoid infinite loops (i doubt thats needed but ...)
864 if(pos+10>buf_size) pos=buf_size; // oops ;)
865
866 return pos;
867 }
868
869 static int h261_decode_frame(AVCodecContext *avctx,
870 void *data, int *data_size,
871 uint8_t *buf, int buf_size)
872 {
873 H261Context *h= avctx->priv_data;
874 MpegEncContext *s = &h->s;
875 int ret;
876 AVFrame *pict = data;
877
878 #ifdef DEBUG
879 av_log(avctx, AV_LOG_DEBUG, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
880 av_log(avctx, AV_LOG_DEBUG, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
881 #endif
882 s->flags= avctx->flags;
883 s->flags2= avctx->flags2;
884
885 h->gob_start_code_skipped=0;
886
887 retry:
888
889 init_get_bits(&s->gb, buf, buf_size*8);
890
891 if(!s->context_initialized){
892 if (MPV_common_init(s) < 0) //we need the idct permutaton for reading a custom matrix
893 return -1;
894 }
895
896 //we need to set current_picture_ptr before reading the header, otherwise we cant store anyting im there
897 if(s->current_picture_ptr==NULL || s->current_picture_ptr->data[0]){
898 int i= ff_find_unused_picture(s, 0);
899 s->current_picture_ptr= &s->picture[i];
900 }
901
902 ret = h261_decode_picture_header(h);
903
904 /* skip if the header was thrashed */
905 if (ret < 0){
906 av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
907 return -1;
908 }
909
910 if (s->width != avctx->coded_width || s->height != avctx->coded_height){
911 ParseContext pc= s->parse_context; //FIXME move these demuxng hack to avformat
912 s->parse_context.buffer=0;
913 MPV_common_end(s);
914 s->parse_context= pc;
915 }
916 if (!s->context_initialized) {
917 avcodec_set_dimensions(avctx, s->width, s->height);
918
919 goto retry;
920 }
921
922 // for hurry_up==5
923 s->current_picture.pict_type= s->pict_type;
924 s->current_picture.key_frame= s->pict_type == I_TYPE;
925
926 /* skip everything if we are in a hurry>=5 */
927 if(avctx->hurry_up>=5) return get_consumed_bytes(s, buf_size);
928 if( (avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type==B_TYPE)
929 ||(avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type!=I_TYPE)
930 || avctx->skip_frame >= AVDISCARD_ALL)
931 return get_consumed_bytes(s, buf_size);
932
933 if(MPV_frame_start(s, avctx) < 0)
934 return -1;
935
936 ff_er_frame_start(s);
937
938 /* decode each macroblock */
939 s->mb_x=0;
940 s->mb_y=0;
941
942 while(h->gob_number < (s->mb_height==18 ? 12 : 5)){
943 if(ff_h261_resync(h)<0)
944 break;
945 h261_decode_gob(h);
946 }
947 MPV_frame_end(s);
948
949 assert(s->current_picture.pict_type == s->current_picture_ptr->pict_type);
950 assert(s->current_picture.pict_type == s->pict_type);
951 *pict= *(AVFrame*)s->current_picture_ptr;
952 ff_print_debug_info(s, pict);
953
954 *data_size = sizeof(AVFrame);
955
956 return get_consumed_bytes(s, buf_size);
957 }
958
959 static int h261_decode_end(AVCodecContext *avctx)
960 {
961 H261Context *h= avctx->priv_data;
962 MpegEncContext *s = &h->s;
963
964 MPV_common_end(s);
965 return 0;
966 }
967
968 #ifdef CONFIG_ENCODERS
969 AVCodec h261_encoder = {
970 "h261",
971 CODEC_TYPE_VIDEO,
972 CODEC_ID_H261,
973 sizeof(H261Context),
974 MPV_encode_init,
975 MPV_encode_picture,
976 MPV_encode_end,
977 .pix_fmts= (enum PixelFormat[]){PIX_FMT_YUV420P, -1},
978 };
979 #endif
980
981 AVCodec h261_decoder = {
982 "h261",
983 CODEC_TYPE_VIDEO,
984 CODEC_ID_H261,
985 sizeof(H261Context),
986 h261_decode_init,
987 NULL,
988 h261_decode_end,
989 h261_decode_frame,
990 CODEC_CAP_DR1,
991 };