FFmpeg
h261dec.c
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1 /*
2  * H.261 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
25  * H.261 decoder.
26  */
27 
28 #include "libavutil/avassert.h"
29 #include "avcodec.h"
30 #include "mpeg_er.h"
31 #include "mpegutils.h"
32 #include "mpegvideo.h"
33 #include "h263.h"
34 #include "h261.h"
35 #include "internal.h"
36 
37 #define H261_MBA_VLC_BITS 9
38 #define H261_MTYPE_VLC_BITS 6
39 #define H261_MV_VLC_BITS 7
40 #define H261_CBP_VLC_BITS 9
41 #define TCOEFF_VLC_BITS 9
42 #define MBA_STUFFING 33
43 #define MBA_STARTCODE 34
44 
49 
51 {
52  static int done = 0;
53 
54  if (!done) {
55  done = 1;
57  ff_h261_mba_bits, 1, 1,
58  ff_h261_mba_code, 1, 1, 662);
60  ff_h261_mtype_bits, 1, 1,
61  ff_h261_mtype_code, 1, 1, 80);
63  &ff_h261_mv_tab[0][1], 2, 1,
64  &ff_h261_mv_tab[0][0], 2, 1, 144);
66  &ff_h261_cbp_tab[0][1], 2, 1,
67  &ff_h261_cbp_tab[0][0], 2, 1, 512);
69  }
70 }
71 
73 {
74  H261Context *h = avctx->priv_data;
75  MpegEncContext *const s = &h->s;
76 
77  // set defaults
79  ff_mpv_decode_init(s, avctx);
80 
81  s->out_format = FMT_H261;
82  s->low_delay = 1;
83  avctx->pix_fmt = AV_PIX_FMT_YUV420P;
84 
87 
88  h->gob_start_code_skipped = 0;
89 
90  return 0;
91 }
92 
93 /**
94  * Decode the group of blocks header or slice header.
95  * @return <0 if an error occurred
96  */
98 {
99  unsigned int val;
100  MpegEncContext *const s = &h->s;
101 
102  if (!h->gob_start_code_skipped) {
103  /* Check for GOB Start Code */
104  val = show_bits(&s->gb, 15);
105  if (val)
106  return -1;
107 
108  /* We have a GBSC */
109  skip_bits(&s->gb, 16);
110  }
111 
112  h->gob_start_code_skipped = 0;
113 
114  h->gob_number = get_bits(&s->gb, 4); /* GN */
115  s->qscale = get_bits(&s->gb, 5); /* GQUANT */
116 
117  /* Check if gob_number is valid */
118  if (s->mb_height == 18) { // CIF
119  if ((h->gob_number <= 0) || (h->gob_number > 12))
120  return -1;
121  } else { // QCIF
122  if ((h->gob_number != 1) && (h->gob_number != 3) &&
123  (h->gob_number != 5))
124  return -1;
125  }
126 
127  /* GEI */
128  if (skip_1stop_8data_bits(&s->gb) < 0)
129  return AVERROR_INVALIDDATA;
130 
131  if (s->qscale == 0) {
132  av_log(s->avctx, AV_LOG_ERROR, "qscale has forbidden 0 value\n");
133  if (s->avctx->err_recognition & (AV_EF_BITSTREAM | AV_EF_COMPLIANT))
134  return -1;
135  }
136 
137  /* For the first transmitted macroblock in a GOB, MBA is the absolute
138  * address. For subsequent macroblocks, MBA is the difference between
139  * the absolute addresses of the macroblock and the last transmitted
140  * macroblock. */
141  h->current_mba = 0;
142  h->mba_diff = 0;
143 
144  return 0;
145 }
146 
147 /**
148  * Decode the group of blocks / video packet header.
149  * @return <0 if no resync found
150  */
152 {
153  MpegEncContext *const s = &h->s;
154  int left, ret;
155 
156  if (h->gob_start_code_skipped) {
158  if (ret >= 0)
159  return 0;
160  } else {
161  if (show_bits(&s->gb, 15) == 0) {
163  if (ret >= 0)
164  return 0;
165  }
166  // OK, it is not where it is supposed to be ...
167  s->gb = s->last_resync_gb;
168  align_get_bits(&s->gb);
169  left = get_bits_left(&s->gb);
170 
171  for (; left > 15 + 1 + 4 + 5; left -= 8) {
172  if (show_bits(&s->gb, 15) == 0) {
173  GetBitContext bak = s->gb;
174 
176  if (ret >= 0)
177  return 0;
178 
179  s->gb = bak;
180  }
181  skip_bits(&s->gb, 8);
182  }
183  }
184 
185  return -1;
186 }
187 
188 /**
189  * Decode skipped macroblocks.
190  * @return 0
191  */
192 static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2)
193 {
194  MpegEncContext *const s = &h->s;
195  int i;
196 
197  s->mb_intra = 0;
198 
199  for (i = mba1; i < mba2; i++) {
200  int j, xy;
201 
202  s->mb_x = ((h->gob_number - 1) % 2) * 11 + i % 11;
203  s->mb_y = ((h->gob_number - 1) / 2) * 3 + i / 11;
204  xy = s->mb_x + s->mb_y * s->mb_stride;
207 
208  for (j = 0; j < 6; j++)
209  s->block_last_index[j] = -1;
210 
211  s->mv_dir = MV_DIR_FORWARD;
212  s->mv_type = MV_TYPE_16X16;
213  s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
214  s->mv[0][0][0] = 0;
215  s->mv[0][0][1] = 0;
216  s->mb_skipped = 1;
217  h->mtype &= ~MB_TYPE_H261_FIL;
218 
219  if (s->current_picture.motion_val[0]) {
220  int b_stride = 2*s->mb_width + 1;
221  int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
222  s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
223  s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
224  }
225 
226  ff_mpv_reconstruct_mb(s, s->block);
227  }
228 
229  return 0;
230 }
231 
232 static const int mvmap[17] = {
233  0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16
234 };
235 
236 static int decode_mv_component(GetBitContext *gb, int v)
237 {
238  int mv_diff = get_vlc2(gb, h261_mv_vlc.table, H261_MV_VLC_BITS, 2);
239 
240  /* check if mv_diff is valid */
241  if (mv_diff < 0)
242  return v;
243 
244  mv_diff = mvmap[mv_diff];
245 
246  if (mv_diff && !get_bits1(gb))
247  mv_diff = -mv_diff;
248 
249  v += mv_diff;
250  if (v <= -16)
251  v += 32;
252  else if (v >= 16)
253  v -= 32;
254 
255  return v;
256 }
257 
258 /**
259  * Decode a macroblock.
260  * @return <0 if an error occurred
261  */
262 static int h261_decode_block(H261Context *h, int16_t *block, int n, int coded)
263 {
264  MpegEncContext *const s = &h->s;
265  int level, i, j, run;
266  RLTable *rl = &ff_h261_rl_tcoeff;
267  const uint8_t *scan_table;
268 
269  /* For the variable length encoding there are two code tables, one being
270  * used for the first transmitted LEVEL in INTER, INTER + MC and
271  * INTER + MC + FIL blocks, the second for all other LEVELs except the
272  * first one in INTRA blocks which is fixed length coded with 8 bits.
273  * NOTE: The two code tables only differ in one VLC so we handle that
274  * manually. */
275  scan_table = s->intra_scantable.permutated;
276  if (s->mb_intra) {
277  /* DC coef */
278  level = get_bits(&s->gb, 8);
279  // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
280  if ((level & 0x7F) == 0) {
281  av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n",
282  level, s->mb_x, s->mb_y);
283  return -1;
284  }
285  /* The code 1000 0000 is not used, the reconstruction level of 1024
286  * being coded as 1111 1111. */
287  if (level == 255)
288  level = 128;
289  block[0] = level;
290  i = 1;
291  } else if (coded) {
292  // Run Level Code
293  // EOB Not possible for first level when cbp is available (that's why the table is different)
294  // 0 1 1s
295  // * * 0*
296  int check = show_bits(&s->gb, 2);
297  i = 0;
298  if (check & 0x2) {
299  skip_bits(&s->gb, 2);
300  block[0] = (check & 0x1) ? -1 : 1;
301  i = 1;
302  }
303  } else {
304  i = 0;
305  }
306  if (!coded) {
307  s->block_last_index[n] = i - 1;
308  return 0;
309  }
310  {
311  OPEN_READER(re, &s->gb);
312  i--; // offset by -1 to allow direct indexing of scan_table
313  for (;;) {
314  UPDATE_CACHE(re, &s->gb);
315  GET_RL_VLC(level, run, re, &s->gb, rl->rl_vlc[0], TCOEFF_VLC_BITS, 2, 0);
316  if (run == 66) {
317  if (level) {
318  CLOSE_READER(re, &s->gb);
319  av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n",
320  s->mb_x, s->mb_y);
321  return -1;
322  }
323  /* escape */
324  /* The remaining combinations of (run, level) are encoded with a
325  * 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits
326  * level. */
327  run = SHOW_UBITS(re, &s->gb, 6) + 1;
328  SKIP_CACHE(re, &s->gb, 6);
329  level = SHOW_SBITS(re, &s->gb, 8);
330  SKIP_COUNTER(re, &s->gb, 6 + 8);
331  } else if (level == 0) {
332  break;
333  } else {
334  if (SHOW_UBITS(re, &s->gb, 1))
335  level = -level;
336  SKIP_COUNTER(re, &s->gb, 1);
337  }
338  i += run;
339  if (i >= 64) {
340  CLOSE_READER(re, &s->gb);
341  av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n",
342  s->mb_x, s->mb_y);
343  return -1;
344  }
345  j = scan_table[i];
346  block[j] = level;
347  }
348  CLOSE_READER(re, &s->gb);
349  }
350  s->block_last_index[n] = i;
351  return 0;
352 }
353 
355 {
356  MpegEncContext *const s = &h->s;
357  int i, cbp, xy;
358 
359  cbp = 63;
360  // Read mba
361  do {
362  h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table,
363  H261_MBA_VLC_BITS, 2);
364 
365  /* Check for slice end */
366  /* NOTE: GOB can be empty (no MB data) or exist only of MBA_stuffing */
367  if (h->mba_diff == MBA_STARTCODE) { // start code
368  h->gob_start_code_skipped = 1;
369  return SLICE_END;
370  }
371  } while (h->mba_diff == MBA_STUFFING); // stuffing
372 
373  if (h->mba_diff < 0) {
374  if (get_bits_left(&s->gb) <= 7)
375  return SLICE_END;
376 
377  av_log(s->avctx, AV_LOG_ERROR, "illegal mba at %d %d\n", s->mb_x, s->mb_y);
378  return SLICE_ERROR;
379  }
380 
381  h->mba_diff += 1;
382  h->current_mba += h->mba_diff;
383 
384  if (h->current_mba > MBA_STUFFING)
385  return SLICE_ERROR;
386 
387  s->mb_x = ((h->gob_number - 1) % 2) * 11 + ((h->current_mba - 1) % 11);
388  s->mb_y = ((h->gob_number - 1) / 2) * 3 + ((h->current_mba - 1) / 11);
389  xy = s->mb_x + s->mb_y * s->mb_stride;
392 
393  // Read mtype
394  h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2);
395  if (h->mtype < 0) {
396  av_log(s->avctx, AV_LOG_ERROR, "Invalid mtype index %d\n",
397  h->mtype);
398  return SLICE_ERROR;
399  }
401  h->mtype = ff_h261_mtype_map[h->mtype];
402 
403  // Read mquant
404  if (IS_QUANT(h->mtype))
405  ff_set_qscale(s, get_bits(&s->gb, 5));
406 
407  s->mb_intra = IS_INTRA4x4(h->mtype);
408 
409  // Read mv
410  if (IS_16X16(h->mtype)) {
411  /* Motion vector data is included for all MC macroblocks. MVD is
412  * obtained from the macroblock vector by subtracting the vector
413  * of the preceding macroblock. For this calculation the vector
414  * of the preceding macroblock is regarded as zero in the
415  * following three situations:
416  * 1) evaluating MVD for macroblocks 1, 12 and 23;
417  * 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1;
418  * 3) MTYPE of the previous macroblock was not MC. */
419  if ((h->current_mba == 1) || (h->current_mba == 12) ||
420  (h->current_mba == 23) || (h->mba_diff != 1)) {
421  h->current_mv_x = 0;
422  h->current_mv_y = 0;
423  }
424 
425  h->current_mv_x = decode_mv_component(&s->gb, h->current_mv_x);
426  h->current_mv_y = decode_mv_component(&s->gb, h->current_mv_y);
427  } else {
428  h->current_mv_x = 0;
429  h->current_mv_y = 0;
430  }
431 
432  // Read cbp
433  if (HAS_CBP(h->mtype))
434  cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1;
435 
436  if (s->mb_intra) {
437  s->current_picture.mb_type[xy] = MB_TYPE_INTRA;
438  goto intra;
439  }
440 
441  //set motion vectors
442  s->mv_dir = MV_DIR_FORWARD;
443  s->mv_type = MV_TYPE_16X16;
444  s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
445  s->mv[0][0][0] = h->current_mv_x * 2; // gets divided by 2 in motion compensation
446  s->mv[0][0][1] = h->current_mv_y * 2;
447 
448  if (s->current_picture.motion_val[0]) {
449  int b_stride = 2*s->mb_width + 1;
450  int b_xy = 2 * s->mb_x + (2 * s->mb_y) * b_stride;
451  s->current_picture.motion_val[0][b_xy][0] = s->mv[0][0][0];
452  s->current_picture.motion_val[0][b_xy][1] = s->mv[0][0][1];
453  }
454 
455 intra:
456  /* decode each block */
457  if (s->mb_intra || HAS_CBP(h->mtype)) {
458  s->bdsp.clear_blocks(s->block[0]);
459  for (i = 0; i < 6; i++) {
460  if (h261_decode_block(h, s->block[i], i, cbp & 32) < 0)
461  return SLICE_ERROR;
462  cbp += cbp;
463  }
464  } else {
465  for (i = 0; i < 6; i++)
466  s->block_last_index[i] = -1;
467  }
468 
469  ff_mpv_reconstruct_mb(s, s->block);
470 
471  return SLICE_OK;
472 }
473 
474 /**
475  * Decode the H.261 picture header.
476  * @return <0 if no startcode found
477  */
479 {
480  MpegEncContext *const s = &h->s;
481  int format, i;
482  uint32_t startcode = 0;
483 
484  for (i = get_bits_left(&s->gb); i > 24; i -= 1) {
485  startcode = ((startcode << 1) | get_bits(&s->gb, 1)) & 0x000FFFFF;
486 
487  if (startcode == 0x10)
488  break;
489  }
490 
491  if (startcode != 0x10) {
492  av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
493  return -1;
494  }
495 
496  /* temporal reference */
497  i = get_bits(&s->gb, 5); /* picture timestamp */
498  if (i < (s->picture_number & 31))
499  i += 32;
500  s->picture_number = (s->picture_number & ~31) + i;
501 
502  s->avctx->framerate = (AVRational) { 30000, 1001 };
503 
504  /* PTYPE starts here */
505  skip_bits1(&s->gb); /* split screen off */
506  skip_bits1(&s->gb); /* camera off */
507  skip_bits1(&s->gb); /* freeze picture release off */
508 
509  format = get_bits1(&s->gb);
510 
511  // only 2 formats possible
512  if (format == 0) { // QCIF
513  s->width = 176;
514  s->height = 144;
515  s->mb_width = 11;
516  s->mb_height = 9;
517  } else { // CIF
518  s->width = 352;
519  s->height = 288;
520  s->mb_width = 22;
521  s->mb_height = 18;
522  }
523 
524  s->mb_num = s->mb_width * s->mb_height;
525 
526  skip_bits1(&s->gb); /* still image mode off */
527  skip_bits1(&s->gb); /* Reserved */
528 
529  /* PEI */
530  if (skip_1stop_8data_bits(&s->gb) < 0)
531  return AVERROR_INVALIDDATA;
532 
533  /* H.261 has no I-frames, but if we pass AV_PICTURE_TYPE_I for the first
534  * frame, the codec crashes if it does not contain all I-blocks
535  * (e.g. when a packet is lost). */
536  s->pict_type = AV_PICTURE_TYPE_P;
537 
538  h->gob_number = 0;
539  return 0;
540 }
541 
543 {
544  MpegEncContext *const s = &h->s;
545 
546  ff_set_qscale(s, s->qscale);
547 
548  /* decode mb's */
549  while (h->current_mba <= MBA_STUFFING) {
550  int ret;
551  /* DCT & quantize */
552  ret = h261_decode_mb(h);
553  if (ret < 0) {
554  if (ret == SLICE_END) {
555  h261_decode_mb_skipped(h, h->current_mba, 33);
556  return 0;
557  }
558  av_log(s->avctx, AV_LOG_ERROR, "Error at MB: %d\n",
559  s->mb_x + s->mb_y * s->mb_stride);
560  return -1;
561  }
562 
564  h->current_mba - h->mba_diff,
565  h->current_mba - 1);
566  }
567 
568  return -1;
569 }
570 
571 /**
572  * returns the number of bytes consumed for building the current frame
573  */
574 static int get_consumed_bytes(MpegEncContext *s, int buf_size)
575 {
576  int pos = get_bits_count(&s->gb) >> 3;
577  if (pos == 0)
578  pos = 1; // avoid infinite loops (i doubt that is needed but ...)
579  if (pos + 10 > buf_size)
580  pos = buf_size; // oops ;)
581 
582  return pos;
583 }
584 
585 static int h261_decode_frame(AVCodecContext *avctx, void *data,
586  int *got_frame, AVPacket *avpkt)
587 {
588  const uint8_t *buf = avpkt->data;
589  int buf_size = avpkt->size;
590  H261Context *h = avctx->priv_data;
591  MpegEncContext *s = &h->s;
592  int ret;
593  AVFrame *pict = data;
594 
595  ff_dlog(avctx, "*****frame %d size=%d\n", avctx->frame_number, buf_size);
596  ff_dlog(avctx, "bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);
597 
598  h->gob_start_code_skipped = 0;
599 
600 retry:
601  init_get_bits(&s->gb, buf, buf_size * 8);
602 
603  if (!s->context_initialized)
604  // we need the IDCT permutation for reading a custom matrix
606 
608 
609  /* skip if the header was thrashed */
610  if (ret < 0) {
611  av_log(s->avctx, AV_LOG_ERROR, "header damaged\n");
612  return -1;
613  }
614 
615  if (s->width != avctx->coded_width || s->height != avctx->coded_height) {
616  ParseContext pc = s->parse_context; // FIXME move this demuxing hack to libavformat
617  s->parse_context.buffer = 0;
619  s->parse_context = pc;
620  }
621 
622  if (!s->context_initialized) {
623  if ((ret = ff_mpv_common_init(s)) < 0)
624  return ret;
625 
626  ret = ff_set_dimensions(avctx, s->width, s->height);
627  if (ret < 0)
628  return ret;
629 
630  goto retry;
631  }
632 
633  // for skipping the frame
634  s->current_picture.f->pict_type = s->pict_type;
635  s->current_picture.f->key_frame = s->pict_type == AV_PICTURE_TYPE_I;
636 
637  if ((avctx->skip_frame >= AVDISCARD_NONREF && s->pict_type == AV_PICTURE_TYPE_B) ||
638  (avctx->skip_frame >= AVDISCARD_NONKEY && s->pict_type != AV_PICTURE_TYPE_I) ||
639  avctx->skip_frame >= AVDISCARD_ALL)
640  return get_consumed_bytes(s, buf_size);
641 
642  if (ff_mpv_frame_start(s, avctx) < 0)
643  return -1;
644 
646 
647  /* decode each macroblock */
648  s->mb_x = 0;
649  s->mb_y = 0;
650 
651  while (h->gob_number < (s->mb_height == 18 ? 12 : 5)) {
652  if (h261_resync(h) < 0)
653  break;
655  }
657 
658  av_assert0(s->current_picture.f->pict_type == s->current_picture_ptr->f->pict_type);
659  av_assert0(s->current_picture.f->pict_type == s->pict_type);
660 
661  if ((ret = av_frame_ref(pict, s->current_picture_ptr->f)) < 0)
662  return ret;
663  ff_print_debug_info(s, s->current_picture_ptr, pict);
664 
665  *got_frame = 1;
666 
667  return get_consumed_bytes(s, buf_size);
668 }
669 
671 {
672  H261Context *h = avctx->priv_data;
673  MpegEncContext *s = &h->s;
674 
676  return 0;
677 }
678 
680  .name = "h261",
681  .long_name = NULL_IF_CONFIG_SMALL("H.261"),
682  .type = AVMEDIA_TYPE_VIDEO,
683  .id = AV_CODEC_ID_H261,
684  .priv_data_size = sizeof(H261Context),
686  .close = h261_decode_end,
688  .capabilities = AV_CODEC_CAP_DR1,
689  .max_lowres = 3,
690 };
ff_mpv_common_init
av_cold int ff_mpv_common_init(MpegEncContext *s)
init common structure for both encoder and decoder.
Definition: mpegvideo.c:890
IS_INTRA4x4
#define IS_INTRA4x4(a)
Definition: mpegutils.h:75
AVCodec
AVCodec.
Definition: codec.h:190
MB_TYPE_L0
#define MB_TYPE_L0
Definition: mpegutils.h:67
MV_TYPE_16X16
#define MV_TYPE_16X16
1 vector for the whole mb
Definition: mpegvideo.h:266
H261_MV_VLC_BITS
#define H261_MV_VLC_BITS
Definition: h261dec.c:39
level
uint8_t level
Definition: svq3.c:210
MBA_STARTCODE
#define MBA_STARTCODE
Definition: h261dec.c:43
init
static av_cold int init(AVCodecContext *avctx)
Definition: avrndec.c:35
get_bits_left
static int get_bits_left(GetBitContext *gb)
Definition: get_bits.h:849
H261_CBP_VLC_BITS
#define H261_CBP_VLC_BITS
Definition: h261dec.c:40
INIT_VLC_STATIC
#define INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size)
Definition: vlc.h:75
get_bits_count
static int get_bits_count(const GetBitContext *s)
Definition: get_bits.h:219
AVFrame
This structure describes decoded (raw) audio or video data.
Definition: frame.h:300
internal.h
AVPacket::data
uint8_t * data
Definition: packet.h:355
H261_MBA_VLC_BITS
#define H261_MBA_VLC_BITS
Definition: h261dec.c:37
h261_decode_block
static int h261_decode_block(H261Context *h, int16_t *block, int n, int coded)
Decode a macroblock.
Definition: h261dec.c:262
data
const char data[16]
Definition: mxf.c:91
MB_TYPE_16x16
#define MB_TYPE_16x16
Definition: mpegutils.h:54
get_vlc2
static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE(*table)[2], int bits, int max_depth)
Parse a vlc code.
Definition: get_bits.h:797
ff_init_block_index
void ff_init_block_index(MpegEncContext *s)
Definition: mpegvideo.c:2279
mpegvideo.h
AV_EF_COMPLIANT
#define AV_EF_COMPLIANT
consider all spec non compliances as errors
Definition: avcodec.h:1670
UPDATE_CACHE
#define UPDATE_CACHE(name, gb)
Definition: get_bits.h:178
mpegutils.h
init_get_bits
static int init_get_bits(GetBitContext *s, const uint8_t *buffer, int bit_size)
Initialize GetBitContext.
Definition: get_bits.h:659
AV_CODEC_ID_H261
@ AV_CODEC_ID_H261
Definition: codec_id.h:52
get_consumed_bytes
static int get_consumed_bytes(MpegEncContext *s, int buf_size)
returns the number of bytes consumed for building the current frame
Definition: h261dec.c:574
skip_bits
static void skip_bits(GetBitContext *s, int n)
Definition: get_bits.h:467
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:379
MBA_STUFFING
#define MBA_STUFFING
Definition: h261dec.c:42
ff_h261_mtype_map
const int ff_h261_mtype_map[10]
Definition: h261data.c:75
ParseContext
Definition: parser.h:28
ff_h261_decoder
AVCodec ff_h261_decoder
Definition: h261dec.c:679
SKIP_CACHE
#define SKIP_CACHE(name, gb, num)
Definition: get_bits.h:180
AVCodecContext::skip_frame
enum AVDiscard skip_frame
Skip decoding for selected frames.
Definition: avcodec.h:2004
h261.h
RLTable
RLTable.
Definition: rl.h:39
GetBitContext
Definition: get_bits.h:61
val
static double val(void *priv, double ch)
Definition: aeval.c:76
AVCodecContext::coded_height
int coded_height
Definition: avcodec.h:714
SLICE_END
#define SLICE_END
end marker found
Definition: mpegvideo.h:518
HAS_CBP
#define HAS_CBP(a)
Definition: mpegutils.h:101
AV_EF_BITSTREAM
#define AV_EF_BITSTREAM
detect bitstream specification deviations
Definition: avcodec.h:1664
ff_mpv_common_end
void ff_mpv_common_end(MpegEncContext *s)
Definition: mpegvideo.c:1138
avassert.h
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
av_cold
#define av_cold
Definition: attributes.h:90
h261_mtype_vlc
static VLC h261_mtype_vlc
Definition: h261dec.c:46
check
#define check(x, y, S, v)
Definition: motion_est_template.c:404
CLOSE_READER
#define CLOSE_READER(name, gb)
Definition: get_bits.h:149
decode
static void decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame, FILE *outfile)
Definition: decode_audio.c:71
h261_decode_picture_header
static int h261_decode_picture_header(H261Context *h)
Decode the H.261 picture header.
Definition: h261dec.c:478
h261_decode_init
static av_cold int h261_decode_init(AVCodecContext *avctx)
Definition: h261dec.c:72
s
#define s(width, name)
Definition: cbs_vp9.c:257
format
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample format(the sample packing is implied by the sample format) and sample rate. The lists are not just lists
SHOW_SBITS
#define SHOW_SBITS(name, gb, num)
Definition: get_bits.h:212
ff_h261_mba_code
const uint8_t ff_h261_mba_code[35]
Definition: h261data.c:34
ff_mpeg_er_frame_start
void ff_mpeg_er_frame_start(MpegEncContext *s)
Definition: mpeg_er.c:46
FMT_H261
@ FMT_H261
Definition: mpegutils.h:125
av_assert0
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
h261_decode_frame
static int h261_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
Definition: h261dec.c:585
h261_decode_end
static av_cold int h261_decode_end(AVCodecContext *avctx)
Definition: h261dec.c:670
ff_h261_mv_tab
const uint8_t ff_h261_mv_tab[17][2]
Definition: h261data.c:89
AV_PIX_FMT_YUV420P
@ AV_PIX_FMT_YUV420P
planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)
Definition: pixfmt.h:66
if
if(ret)
Definition: filter_design.txt:179
AVDISCARD_ALL
@ AVDISCARD_ALL
discard all
Definition: avcodec.h:236
h261_decode_gob_header
static int h261_decode_gob_header(H261Context *h)
Decode the group of blocks header or slice header.
Definition: h261dec.c:97
run
uint8_t run
Definition: svq3.c:209
ff_mpv_idct_init
av_cold void ff_mpv_idct_init(MpegEncContext *s)
Definition: mpegvideo.c:329
AVRational
Rational number (pair of numerator and denominator).
Definition: rational.h:58
h261_decode_init_vlc
static av_cold void h261_decode_init_vlc(H261Context *h)
Definition: h261dec.c:50
AV_PICTURE_TYPE_I
@ AV_PICTURE_TYPE_I
Intra.
Definition: avutil.h:274
get_bits1
static unsigned int get_bits1(GetBitContext *s)
Definition: get_bits.h:498
ff_set_qscale
void ff_set_qscale(MpegEncContext *s, int qscale)
set qscale and update qscale dependent variables.
Definition: mpegvideo.c:2343
ff_dlog
#define ff_dlog(a,...)
Definition: tableprint_vlc.h:29
AVDISCARD_NONKEY
@ AVDISCARD_NONKEY
discard all frames except keyframes
Definition: avcodec.h:235
AV_CODEC_CAP_DR1
#define AV_CODEC_CAP_DR1
Codec uses get_buffer() for allocating buffers and supports custom allocators.
Definition: codec.h:50
AVPacket::size
int size
Definition: packet.h:356
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:188
av_frame_ref
int av_frame_ref(AVFrame *dst, const AVFrame *src)
Set up a new reference to the data described by the source frame.
Definition: frame.c:444
MB_TYPE_SKIP
#define MB_TYPE_SKIP
Definition: mpegutils.h:62
ff_h261_common_init
av_cold void ff_h261_common_init(void)
Definition: h261.c:83
OPEN_READER
#define OPEN_READER(name, gb)
Definition: get_bits.h:138
skip_bits1
static void skip_bits1(GetBitContext *s)
Definition: get_bits.h:538
ff_print_debug_info
void ff_print_debug_info(MpegEncContext *s, Picture *p, AVFrame *pict)
Definition: mpegvideo.c:1444
IS_16X16
#define IS_16X16(a)
Definition: mpegutils.h:86
H261Context
H261Context.
Definition: h261.h:37
H261_MTYPE_VLC_BITS
#define H261_MTYPE_VLC_BITS
Definition: h261dec.c:38
ff_update_block_index
static void ff_update_block_index(MpegEncContext *s)
Definition: mpegvideo.h:740
mvmap
static const int mvmap[17]
Definition: h261dec.c:232
SKIP_COUNTER
#define SKIP_COUNTER(name, gb, num)
Definition: get_bits.h:185
ff_h261_cbp_tab
const uint8_t ff_h261_cbp_tab[63][2]
Definition: h261data.c:95
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:269
show_bits
static unsigned int show_bits(GetBitContext *s, int n)
Show 1-25 bits.
Definition: get_bits.h:446
h261_mv_vlc
static VLC h261_mv_vlc
Definition: h261dec.c:47
IS_QUANT
#define IS_QUANT(a)
Definition: mpegutils.h:95
h261_decode_gob
static int h261_decode_gob(H261Context *h)
Definition: h261dec.c:542
uint8_t
uint8_t
Definition: audio_convert.c:194
ff_h261_mtype_code
const uint8_t ff_h261_mtype_code[10]
Definition: h261data.c:63
AVCodec::name
const char * name
Name of the codec implementation.
Definition: codec.h:197
ff_mpv_decode_defaults
void ff_mpv_decode_defaults(MpegEncContext *s)
Set the given MpegEncContext to defaults for decoding.
Definition: mpegvideo.c:667
AVCodecContext::pix_fmt
enum AVPixelFormat pix_fmt
Pixel format, see AV_PIX_FMT_xxx.
Definition: avcodec.h:736
ff_mpv_frame_end
void ff_mpv_frame_end(MpegEncContext *s)
Definition: mpegvideo.c:1436
h261_resync
static int h261_resync(H261Context *h)
Decode the group of blocks / video packet header.
Definition: h261dec.c:151
avcodec.h
GET_RL_VLC
#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update)
Definition: get_bits.h:738
ret
ret
Definition: filter_design.txt:187
SLICE_OK
#define SLICE_OK
Definition: mpegvideo.h:516
h261_mba_vlc
static VLC h261_mba_vlc
Definition: h261dec.c:45
align_get_bits
static const uint8_t * align_get_bits(GetBitContext *s)
Definition: get_bits.h:693
ff_mpv_frame_start
int ff_mpv_frame_start(MpegEncContext *s, AVCodecContext *avctx)
generic function called after decoding the header and before a frame is decoded.
Definition: mpegvideo.c:1212
pos
unsigned int pos
Definition: spdifenc.c:412
left
Tag MUST be and< 10hcoeff half pel interpolation filter coefficients, hcoeff[0] are the 2 middle coefficients[1] are the next outer ones and so on, resulting in a filter like:...eff[2], hcoeff[1], hcoeff[0], hcoeff[0], hcoeff[1], hcoeff[2] ... the sign of the coefficients is not explicitly stored but alternates after each coeff and coeff[0] is positive, so ...,+,-,+,-,+,+,-,+,-,+,... hcoeff[0] is not explicitly stored but found by subtracting the sum of all stored coefficients with signs from 32 hcoeff[0]=32 - hcoeff[1] - hcoeff[2] - ... a good choice for hcoeff and htaps is htaps=6 hcoeff={40,-10, 2} an alternative which requires more computations at both encoder and decoder side and may or may not be better is htaps=8 hcoeff={42,-14, 6,-2}ref_frames minimum of the number of available reference frames and max_ref_frames for example the first frame after a key frame always has ref_frames=1spatial_decomposition_type wavelet type 0 is a 9/7 symmetric compact integer wavelet 1 is a 5/3 symmetric compact integer wavelet others are reserved stored as delta from last, last is reset to 0 if always_reset||keyframeqlog quality(logarithmic quantizer scale) stored as delta from last, last is reset to 0 if always_reset||keyframemv_scale stored as delta from last, last is reset to 0 if always_reset||keyframe FIXME check that everything works fine if this changes between framesqbias dequantization bias stored as delta from last, last is reset to 0 if always_reset||keyframeblock_max_depth maximum depth of the block tree stored as delta from last, last is reset to 0 if always_reset||keyframequant_table quantization tableHighlevel bitstream structure:==============================--------------------------------------------|Header|--------------------------------------------|------------------------------------|||Block0||||split?||||yes no||||......... intra?||||:Block01 :yes no||||:Block02 :....... ..........||||:Block03 ::y DC ::ref index:||||:Block04 ::cb DC ::motion x :||||......... :cr DC ::motion y :||||....... ..........|||------------------------------------||------------------------------------|||Block1|||...|--------------------------------------------|------------ ------------ ------------|||Y subbands||Cb subbands||Cr subbands||||--- ---||--- ---||--- ---|||||LL0||HL0||||LL0||HL0||||LL0||HL0|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||LH0||HH0||||LH0||HH0||||LH0||HH0|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||HL1||LH1||||HL1||LH1||||HL1||LH1|||||--- ---||--- ---||--- ---||||--- ---||--- ---||--- ---|||||HH1||HL2||||HH1||HL2||||HH1||HL2|||||...||...||...|||------------ ------------ ------------|--------------------------------------------Decoding process:=================------------|||Subbands|------------||||------------|Intra DC||||LL0 subband prediction ------------|\ Dequantization ------------------- \||Reference frames|\ IDWT|------- -------|Motion \|||Frame 0||Frame 1||Compensation . OBMC v -------|------- -------|--------------. \------> Frame n output Frame Frame<----------------------------------/|...|------------------- Range Coder:============Binary Range Coder:------------------- The implemented range coder is an adapted version based upon "Range encoding: an algorithm for removing redundancy from a digitised message." by G. N. N. Martin. The symbols encoded by the Snow range coder are bits(0|1). The associated probabilities are not fix but change depending on the symbol mix seen so far. bit seen|new state ---------+----------------------------------------------- 0|256 - state_transition_table[256 - old_state];1|state_transition_table[old_state];state_transition_table={ 0, 0, 0, 0, 0, 0, 0, 0, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 190, 191, 192, 194, 194, 195, 196, 197, 198, 199, 200, 201, 202, 202, 204, 205, 206, 207, 208, 209, 209, 210, 211, 212, 213, 215, 215, 216, 217, 218, 219, 220, 220, 222, 223, 224, 225, 226, 227, 227, 229, 229, 230, 231, 232, 234, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 248, 0, 0, 0, 0, 0, 0, 0};FIXME Range Coding of integers:------------------------- FIXME Neighboring Blocks:===================left and top are set to the respective blocks unless they are outside of the image in which case they are set to the Null block top-left is set to the top left block unless it is outside of the image in which case it is set to the left block if this block has no larger parent block or it is at the left side of its parent block and the top right block is not outside of the image then the top right block is used for top-right else the top-left block is used Null block y, cb, cr are 128 level, ref, mx and my are 0 Motion Vector Prediction:=========================1. the motion vectors of all the neighboring blocks are scaled to compensate for the difference of reference frames scaled_mv=(mv *(256 *(current_reference+1)/(mv.reference+1))+128)> the median of the scaled left
Definition: snow.txt:386
FF_ARRAY_ELEMS
#define FF_ARRAY_ELEMS(a)
Definition: sinewin_tablegen_template.c:38
ff_h261_rl_tcoeff
RLTable ff_h261_rl_tcoeff
Definition: h261data.c:150
skip_1stop_8data_bits
static int skip_1stop_8data_bits(GetBitContext *gb)
Definition: get_bits.h:854
AVCodecContext
main external API structure.
Definition: avcodec.h:526
h261_cbp_vlc
static VLC h261_cbp_vlc
Definition: h261dec.c:48
SHOW_UBITS
#define SHOW_UBITS(name, gb, num)
Definition: get_bits.h:211
AV_PICTURE_TYPE_B
@ AV_PICTURE_TYPE_B
Bi-dir predicted.
Definition: avutil.h:276
VLC
Definition: vlc.h:26
ff_h261_mtype_bits
const uint8_t ff_h261_mtype_bits[10]
Definition: h261data.c:69
ff_mpv_reconstruct_mb
void ff_mpv_reconstruct_mb(MpegEncContext *s, int16_t block[12][64])
Definition: mpegvideo.c:2260
h261_decode_mb_skipped
static int h261_decode_mb_skipped(H261Context *h, int mba1, int mba2)
Decode skipped macroblocks.
Definition: h261dec.c:192
INIT_VLC_RL
#define INIT_VLC_RL(rl, static_size)
Definition: rl.h:63
AVCodecContext::coded_width
int coded_width
Bitstream width / height, may be different from width/height e.g.
Definition: avcodec.h:714
AV_PICTURE_TYPE_P
@ AV_PICTURE_TYPE_P
Predicted.
Definition: avutil.h:275
AVMEDIA_TYPE_VIDEO
@ AVMEDIA_TYPE_VIDEO
Definition: avutil.h:201
ff_set_dimensions
int ff_set_dimensions(AVCodecContext *s, int width, int height)
Check that the provided frame dimensions are valid and set them on the codec context.
Definition: utils.c:104
AVCodecContext::frame_number
int frame_number
Frame counter, set by libavcodec.
Definition: avcodec.h:1217
h261_decode_mb
static int h261_decode_mb(H261Context *h)
Definition: h261dec.c:354
SLICE_ERROR
#define SLICE_ERROR
Definition: mpegvideo.h:517
MV_DIR_FORWARD
#define MV_DIR_FORWARD
Definition: mpegvideo.h:262
AVPacket
This structure stores compressed data.
Definition: packet.h:332
AVCodecContext::priv_data
void * priv_data
Definition: avcodec.h:553
decode_mv_component
static int decode_mv_component(GetBitContext *gb, int v)
Definition: h261dec.c:236
mpeg_er.h
block
The exact code depends on how similar the blocks are and how related they are to the block
Definition: filter_design.txt:207
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
h
h
Definition: vp9dsp_template.c:2038
ff_mpv_decode_init
void ff_mpv_decode_init(MpegEncContext *s, AVCodecContext *avctx)
Definition: mpegvideo.c:672
AVDISCARD_NONREF
@ AVDISCARD_NONREF
discard all non reference
Definition: avcodec.h:232
ff_h261_mba_bits
const uint8_t ff_h261_mba_bits[35]
Definition: h261data.c:48
MpegEncContext
MpegEncContext.
Definition: mpegvideo.h:81
VLC::table
VLC_TYPE(* table)[2]
code, bits
Definition: vlc.h:28
TCOEFF_VLC_BITS
#define TCOEFF_VLC_BITS
Definition: h261dec.c:41
RLTable::rl_vlc
RL_VLC_ELEM * rl_vlc[32]
decoding only
Definition: rl.h:48
MB_TYPE_INTRA
#define MB_TYPE_INTRA
Definition: mpegutils.h:73
re
float re
Definition: fft.c:82
h263.h
MB_TYPE_H261_FIL
#define MB_TYPE_H261_FIL
Definition: h261.h:49