FFmpeg
cafdec.c
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1 /*
2  * Core Audio Format demuxer
3  * Copyright (c) 2007 Justin Ruggles
4  * Copyright (c) 2009 Peter Ross
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  * Core Audio Format demuxer
26  */
27 
28 #include <inttypes.h>
29 
30 #include "avformat.h"
31 #include "internal.h"
32 #include "isom.h"
33 #include "mov_chan.h"
34 #include "libavutil/intreadwrite.h"
35 #include "libavutil/intfloat.h"
36 #include "libavutil/dict.h"
37 #include "caf.h"
38 
39 typedef struct CafContext {
40  int bytes_per_packet; ///< bytes in a packet, or 0 if variable
41  int frames_per_packet; ///< frames in a packet, or 0 if variable
42  int64_t num_bytes; ///< total number of bytes in stream
43 
44  int64_t packet_cnt; ///< packet counter
45  int64_t frame_cnt; ///< frame counter
46 
47  int64_t data_start; ///< data start position, in bytes
48  int64_t data_size; ///< raw data size, in bytes
49 } CafContext;
50 
51 static int probe(const AVProbeData *p)
52 {
53  if (AV_RB32(p->buf) == MKBETAG('c','a','f','f') && AV_RB16(&p->buf[4]) == 1)
54  return AVPROBE_SCORE_MAX;
55  return 0;
56 }
57 
58 /** Read audio description chunk */
60 {
61  AVIOContext *pb = s->pb;
62  CafContext *caf = s->priv_data;
63  AVStream *st;
64  int flags;
65 
66  /* new audio stream */
67  st = avformat_new_stream(s, NULL);
68  if (!st)
69  return AVERROR(ENOMEM);
70 
71  /* parse format description */
74  st->codecpar->codec_tag = avio_rl32(pb);
75  flags = avio_rb32(pb);
76  caf->bytes_per_packet = avio_rb32(pb);
78  caf->frames_per_packet = avio_rb32(pb);
79  st->codecpar->channels = avio_rb32(pb);
81 
82  /* calculate bit rate for constant size packets */
83  if (caf->frames_per_packet > 0 && caf->bytes_per_packet > 0) {
84  st->codecpar->bit_rate = (uint64_t)st->codecpar->sample_rate * (uint64_t)caf->bytes_per_packet * 8
85  / (uint64_t)caf->frames_per_packet;
86  } else {
87  st->codecpar->bit_rate = 0;
88  }
89 
90  /* determine codec */
91  if (st->codecpar->codec_tag == MKTAG('l','p','c','m'))
93  else
95  return 0;
96 }
97 
98 /** Read magic cookie chunk */
99 static int read_kuki_chunk(AVFormatContext *s, int64_t size)
100 {
101  AVIOContext *pb = s->pb;
102  AVStream *st = s->streams[0];
103  int ret;
104 
106  return -1;
107 
108  if (st->codecpar->codec_id == AV_CODEC_ID_AAC) {
109  /* The magic cookie format for AAC is an mp4 esds atom.
110  The lavc AAC decoder requires the data from the codec specific
111  description as extradata input. */
112  int strt, skip;
113 
114  strt = avio_tell(pb);
115  ff_mov_read_esds(s, pb);
116  skip = size - (avio_tell(pb) - strt);
117  if (skip < 0 || !st->codecpar->extradata ||
119  av_log(s, AV_LOG_ERROR, "invalid AAC magic cookie\n");
120  return AVERROR_INVALIDDATA;
121  }
122  avio_skip(pb, skip);
123  } else if (st->codecpar->codec_id == AV_CODEC_ID_ALAC) {
124 #define ALAC_PREAMBLE 12
125 #define ALAC_HEADER 36
126 #define ALAC_NEW_KUKI 24
127  uint8_t preamble[12];
128  if (size < ALAC_NEW_KUKI) {
129  av_log(s, AV_LOG_ERROR, "invalid ALAC magic cookie\n");
130  avio_skip(pb, size);
131  return AVERROR_INVALIDDATA;
132  }
133  if (avio_read(pb, preamble, ALAC_PREAMBLE) != ALAC_PREAMBLE) {
134  av_log(s, AV_LOG_ERROR, "failed to read preamble\n");
135  return AVERROR_INVALIDDATA;
136  }
137 
138  if ((ret = ff_alloc_extradata(st->codecpar, ALAC_HEADER)) < 0)
139  return ret;
140 
141  /* For the old style cookie, we skip 12 bytes, then read 36 bytes.
142  * The new style cookie only contains the last 24 bytes of what was
143  * 36 bytes in the old style cookie, so we fabricate the first 12 bytes
144  * in that case to maintain compatibility. */
145  if (!memcmp(&preamble[4], "frmaalac", 8)) {
146  if (size < ALAC_PREAMBLE + ALAC_HEADER) {
147  av_log(s, AV_LOG_ERROR, "invalid ALAC magic cookie\n");
148  av_freep(&st->codecpar->extradata);
149  return AVERROR_INVALIDDATA;
150  }
151  if (avio_read(pb, st->codecpar->extradata, ALAC_HEADER) != ALAC_HEADER) {
152  av_log(s, AV_LOG_ERROR, "failed to read kuki header\n");
153  av_freep(&st->codecpar->extradata);
154  return AVERROR_INVALIDDATA;
155  }
156  avio_skip(pb, size - ALAC_PREAMBLE - ALAC_HEADER);
157  } else {
158  AV_WB32(st->codecpar->extradata, 36);
159  memcpy(&st->codecpar->extradata[4], "alac", 4);
160  AV_WB32(&st->codecpar->extradata[8], 0);
161  memcpy(&st->codecpar->extradata[12], preamble, 12);
162  if (avio_read(pb, &st->codecpar->extradata[24], ALAC_NEW_KUKI - 12) != ALAC_NEW_KUKI - 12) {
163  av_log(s, AV_LOG_ERROR, "failed to read new kuki header\n");
164  av_freep(&st->codecpar->extradata);
165  return AVERROR_INVALIDDATA;
166  }
167  avio_skip(pb, size - ALAC_NEW_KUKI);
168  }
169  } else if (st->codecpar->codec_id == AV_CODEC_ID_OPUS) {
170  // The data layout for Opus is currently unknown, so we do not export
171  // extradata at all. Multichannel streams are not supported.
172  if (st->codecpar->channels > 2) {
173  avpriv_request_sample(s, "multichannel Opus in CAF");
174  return AVERROR_PATCHWELCOME;
175  }
176  avio_skip(pb, size);
177  } else if ((ret = ff_get_extradata(s, st->codecpar, pb, size)) < 0) {
178  return ret;
179  }
180 
181  return 0;
182 }
183 
184 /** Read packet table chunk */
185 static int read_pakt_chunk(AVFormatContext *s, int64_t size)
186 {
187  AVIOContext *pb = s->pb;
188  AVStream *st = s->streams[0];
189  CafContext *caf = s->priv_data;
190  int64_t pos = 0, ccount, num_packets;
191  int i;
192 
193  ccount = avio_tell(pb);
194 
195  num_packets = avio_rb64(pb);
196  if (num_packets < 0 || INT32_MAX / sizeof(AVIndexEntry) < num_packets)
197  return AVERROR_INVALIDDATA;
198 
199  st->nb_frames = avio_rb64(pb); /* valid frames */
200  st->nb_frames += avio_rb32(pb); /* priming frames */
201  st->nb_frames += avio_rb32(pb); /* remainder frames */
202 
203  st->duration = 0;
204  for (i = 0; i < num_packets; i++) {
205  av_add_index_entry(s->streams[0], pos, st->duration, 0, 0, AVINDEX_KEYFRAME);
208  }
209 
210  if (avio_tell(pb) - ccount > size) {
211  av_log(s, AV_LOG_ERROR, "error reading packet table\n");
212  return AVERROR_INVALIDDATA;
213  }
214  avio_skip(pb, ccount + size - avio_tell(pb));
215 
216  caf->num_bytes = pos;
217  return 0;
218 }
219 
220 /** Read information chunk */
221 static void read_info_chunk(AVFormatContext *s, int64_t size)
222 {
223  AVIOContext *pb = s->pb;
224  unsigned int i;
225  unsigned int nb_entries = avio_rb32(pb);
226  for (i = 0; i < nb_entries && !avio_feof(pb); i++) {
227  char key[32];
228  char value[1024];
229  avio_get_str(pb, INT_MAX, key, sizeof(key));
230  avio_get_str(pb, INT_MAX, value, sizeof(value));
231  av_dict_set(&s->metadata, key, value, 0);
232  }
233 }
234 
236 {
237  AVIOContext *pb = s->pb;
238  CafContext *caf = s->priv_data;
239  AVStream *st;
240  uint32_t tag = 0;
241  int found_data, ret;
242  int64_t size, pos;
243 
244  avio_skip(pb, 8); /* magic, version, file flags */
245 
246  /* audio description chunk */
247  if (avio_rb32(pb) != MKBETAG('d','e','s','c')) {
248  av_log(s, AV_LOG_ERROR, "desc chunk not present\n");
249  return AVERROR_INVALIDDATA;
250  }
251  size = avio_rb64(pb);
252  if (size != 32)
253  return AVERROR_INVALIDDATA;
254 
255  ret = read_desc_chunk(s);
256  if (ret)
257  return ret;
258  st = s->streams[0];
259 
260  /* parse each chunk */
261  found_data = 0;
262  while (!avio_feof(pb)) {
263 
264  /* stop at data chunk if seeking is not supported or
265  data chunk size is unknown */
266  if (found_data && (caf->data_size < 0 || !(pb->seekable & AVIO_SEEKABLE_NORMAL)))
267  break;
268 
269  tag = avio_rb32(pb);
270  size = avio_rb64(pb);
271  pos = avio_tell(pb);
272  if (avio_feof(pb))
273  break;
274 
275  switch (tag) {
276  case MKBETAG('d','a','t','a'):
277  avio_skip(pb, 4); /* edit count */
278  caf->data_start = avio_tell(pb);
279  caf->data_size = size < 0 ? -1 : size - 4;
280  if (caf->data_size > 0 && (pb->seekable & AVIO_SEEKABLE_NORMAL))
281  avio_skip(pb, caf->data_size);
282  found_data = 1;
283  break;
284 
285  case MKBETAG('c','h','a','n'):
286  if ((ret = ff_mov_read_chan(s, s->pb, st, size)) < 0)
287  return ret;
288  break;
289 
290  /* magic cookie chunk */
291  case MKBETAG('k','u','k','i'):
292  if (read_kuki_chunk(s, size))
293  return AVERROR_INVALIDDATA;
294  break;
295 
296  /* packet table chunk */
297  case MKBETAG('p','a','k','t'):
298  if (read_pakt_chunk(s, size))
299  return AVERROR_INVALIDDATA;
300  break;
301 
302  case MKBETAG('i','n','f','o'):
303  read_info_chunk(s, size);
304  break;
305 
306  default:
308  "skipping CAF chunk: %08"PRIX32" (%s), size %"PRId64"\n",
309  tag, av_fourcc2str(av_bswap32(tag)), size);
310  case MKBETAG('f','r','e','e'):
311  if (size < 0 && found_data)
312  goto found_data;
313  if (size < 0)
314  return AVERROR_INVALIDDATA;
315  break;
316  }
317 
318  if (size > 0) {
319  if (pos > INT64_MAX - size)
320  return AVERROR_INVALIDDATA;
321  avio_skip(pb, FFMAX(0, pos + size - avio_tell(pb)));
322  }
323  }
324 
325  if (!found_data)
326  return AVERROR_INVALIDDATA;
327 
328 found_data:
329  if (caf->bytes_per_packet > 0 && caf->frames_per_packet > 0) {
330  if (caf->data_size > 0)
331  st->nb_frames = (caf->data_size / caf->bytes_per_packet) * caf->frames_per_packet;
332  } else if (st->nb_index_entries && st->duration > 0) {
333  if (st->codecpar->sample_rate && caf->data_size / st->duration > INT64_MAX / st->codecpar->sample_rate / 8) {
334  av_log(s, AV_LOG_ERROR, "Overflow during bit rate calculation %d * 8 * %"PRId64"\n",
335  st->codecpar->sample_rate, caf->data_size / st->duration);
336  return AVERROR_INVALIDDATA;
337  }
338  st->codecpar->bit_rate = st->codecpar->sample_rate * 8LL *
339  (caf->data_size / st->duration);
340  } else {
341  av_log(s, AV_LOG_ERROR, "Missing packet table. It is required when "
342  "block size or frame size are variable.\n");
343  return AVERROR_INVALIDDATA;
344  }
345 
346  avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
347  st->start_time = 0;
348 
349  /* position the stream at the start of data */
350  if (caf->data_size >= 0)
351  avio_seek(pb, caf->data_start, SEEK_SET);
352 
353  return 0;
354 }
355 
356 #define CAF_MAX_PKT_SIZE 4096
357 
359 {
360  AVIOContext *pb = s->pb;
361  AVStream *st = s->streams[0];
362  CafContext *caf = s->priv_data;
363  int res, pkt_size = 0, pkt_frames = 0;
364  int64_t left = CAF_MAX_PKT_SIZE;
365 
366  if (avio_feof(pb))
367  return AVERROR_EOF;
368 
369  /* don't read past end of data chunk */
370  if (caf->data_size > 0) {
371  left = (caf->data_start + caf->data_size) - avio_tell(pb);
372  if (!left)
373  return AVERROR_EOF;
374  if (left < 0)
375  return AVERROR(EIO);
376  }
377 
378  pkt_frames = caf->frames_per_packet;
379  pkt_size = caf->bytes_per_packet;
380 
381  if (pkt_size > 0 && pkt_frames == 1) {
382  pkt_size = (CAF_MAX_PKT_SIZE / pkt_size) * pkt_size;
383  pkt_size = FFMIN(pkt_size, left);
384  pkt_frames = pkt_size / caf->bytes_per_packet;
385  } else if (st->nb_index_entries) {
386  if (caf->packet_cnt < st->nb_index_entries - 1) {
387  pkt_size = st->index_entries[caf->packet_cnt + 1].pos - st->index_entries[caf->packet_cnt].pos;
388  pkt_frames = st->index_entries[caf->packet_cnt + 1].timestamp - st->index_entries[caf->packet_cnt].timestamp;
389  } else if (caf->packet_cnt == st->nb_index_entries - 1) {
390  pkt_size = caf->num_bytes - st->index_entries[caf->packet_cnt].pos;
391  pkt_frames = st->duration - st->index_entries[caf->packet_cnt].timestamp;
392  } else {
393  return AVERROR(EIO);
394  }
395  }
396 
397  if (pkt_size == 0 || pkt_frames == 0 || pkt_size > left)
398  return AVERROR(EIO);
399 
400  res = av_get_packet(pb, pkt, pkt_size);
401  if (res < 0)
402  return res;
403 
404  pkt->size = res;
405  pkt->stream_index = 0;
406  pkt->dts = pkt->pts = caf->frame_cnt;
407 
408  caf->packet_cnt++;
409  caf->frame_cnt += pkt_frames;
410 
411  return 0;
412 }
413 
414 static int read_seek(AVFormatContext *s, int stream_index,
415  int64_t timestamp, int flags)
416 {
417  AVStream *st = s->streams[0];
418  CafContext *caf = s->priv_data;
419  int64_t pos, packet_cnt, frame_cnt;
420 
421  timestamp = FFMAX(timestamp, 0);
422 
423  if (caf->frames_per_packet > 0 && caf->bytes_per_packet > 0) {
424  /* calculate new byte position based on target frame position */
425  pos = caf->bytes_per_packet * (timestamp / caf->frames_per_packet);
426  if (caf->data_size > 0)
427  pos = FFMIN(pos, caf->data_size);
428  packet_cnt = pos / caf->bytes_per_packet;
429  frame_cnt = caf->frames_per_packet * packet_cnt;
430  } else if (st->nb_index_entries) {
431  packet_cnt = av_index_search_timestamp(st, timestamp, flags);
432  frame_cnt = st->index_entries[packet_cnt].timestamp;
433  pos = st->index_entries[packet_cnt].pos;
434  } else {
435  return -1;
436  }
437 
438  if (avio_seek(s->pb, pos + caf->data_start, SEEK_SET) < 0)
439  return -1;
440 
441  caf->packet_cnt = packet_cnt;
442  caf->frame_cnt = frame_cnt;
443 
444  return 0;
445 }
446 
448  .name = "caf",
449  .long_name = NULL_IF_CONFIG_SMALL("Apple CAF (Core Audio Format)"),
450  .priv_data_size = sizeof(CafContext),
451  .read_probe = probe,
454  .read_seek = read_seek,
455  .codec_tag = (const AVCodecTag* const []){ ff_codec_caf_tags, 0 },
456 };
#define NULL
Definition: coverity.c:32
Bytestream IO Context.
Definition: avio.h:161
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
static int read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: cafdec.c:358
int av_add_index_entry(AVStream *st, int64_t pos, int64_t timestamp, int size, int distance, int flags)
Add an index entry into a sorted list.
Definition: utils.c:2049
enum AVCodecID ff_codec_get_id(const AVCodecTag *tags, unsigned int tag)
Definition: utils.c:3160
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
int bytes_per_packet
bytes in a packet, or 0 if variable
Definition: cafdec.c:40
void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: utils.c:4943
int64_t pos
Definition: avformat.h:804
#define avpriv_request_sample(...)
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:4036
int size
Definition: avcodec.h:1534
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
fseek() equivalent for AVIOContext.
Definition: aviobuf.c:241
AVIndexEntry * index_entries
Only used if the format does not support seeking natively.
Definition: avformat.h:1104
CAF common code.
int64_t avio_skip(AVIOContext *s, int64_t offset)
Skip given number of bytes forward.
Definition: aviobuf.c:329
const char * key
static AVPacket pkt
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_RB16
Definition: bytestream.h:87
#define CAF_MAX_PKT_SIZE
Definition: cafdec.c:356
static int read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
Definition: cafdec.c:414
static int read_header(AVFormatContext *s)
Definition: cafdec.c:235
Format I/O context.
Definition: avformat.h:1352
#define ALAC_PREAMBLE
Public dictionary API.
static av_always_inline double av_int2double(uint64_t i)
Reinterpret a 64-bit integer as a double.
Definition: intfloat.h:60
uint8_t
static int read_kuki_chunk(AVFormatContext *s, int64_t size)
Read magic cookie chunk.
Definition: cafdec.c:99
unsigned int avio_rb32(AVIOContext *s)
Definition: aviobuf.c:798
GLsizei GLboolean const GLfloat * value
Definition: opengl_enc.c:108
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:4524
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_RB32
Definition: bytestream.h:87
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1420
uint32_t tag
Definition: movenc.c:1533
#define AVERROR_EOF
End of file.
Definition: error.h:55
int av_get_packet(AVIOContext *s, AVPacket *pkt, int size)
Allocate and read the payload of a packet and initialize its fields with default values.
Definition: utils.c:308
ptrdiff_t size
Definition: opengl_enc.c:100
uint64_t avio_rb64(AVIOContext *s)
Definition: aviobuf.c:919
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:557
#define av_log(a,...)
int avio_read(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:645
int64_t bit_rate
The average bitrate of the encoded data (in bits per second).
Definition: avcodec.h:4065
#define AVINDEX_KEYFRAME
Definition: avformat.h:811
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:259
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
AVDictionary * metadata
Metadata that applies to the whole file.
Definition: avformat.h:1592
int av_index_search_timestamp(AVStream *st, int64_t timestamp, int flags)
Get the index for a specific timestamp.
Definition: utils.c:2166
int ff_mp4_read_descr_len(AVIOContext *pb)
Definition: isom.c:466
unsigned int avio_rl32(AVIOContext *s)
Definition: aviobuf.c:767
int64_t timestamp
Timestamp in AVStream.time_base units, preferably the time from which on correctly decoded frames are...
Definition: avformat.h:805
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
unsigned int pos
Definition: spdifenc.c:410
#define av_fourcc2str(fourcc)
Definition: avutil.h:348
enum AVMediaType codec_type
General type of the encoded data.
Definition: avcodec.h:4032
int64_t num_bytes
total number of bytes in stream
Definition: cafdec.c:42
#define FFMAX(a, b)
Definition: common.h:94
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:443
int block_align
Audio only.
Definition: avcodec.h:4153
int seekable
A combination of AVIO_SEEKABLE_ flags or 0 when the stream is not seekable.
Definition: avio.h:260
int ff_alloc_extradata(AVCodecParameters *par, int size)
Allocate extradata with additional AV_INPUT_BUFFER_PADDING_SIZE at end which is always set to 0...
Definition: utils.c:3323
#define FFMIN(a, b)
Definition: common.h:96
int64_t data_start
data start position, in bytes
Definition: cafdec.c:47
int64_t data_size
raw data size, in bytes
Definition: cafdec.c:48
AVInputFormat ff_caf_demuxer
Definition: cafdec.c:447
#define s(width, name)
Definition: cbs_vp9.c:257
#define ALAC_NEW_KUKI
int ff_mov_read_chan(AVFormatContext *s, AVIOContext *pb, AVStream *st, int64_t size)
Read &#39;chan&#39; tag from the input stream.
Definition: mov_chan.c:547
int ff_mov_read_esds(AVFormatContext *fc, AVIOContext *pb)
Definition: mov_esds.c:23
Stream structure.
Definition: avformat.h:875
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:62
#define AVIO_SEEKABLE_NORMAL
Seeking works like for a local file.
Definition: avio.h:40
#define av_bswap32
Definition: bswap.h:33
AVIOContext * pb
I/O context.
Definition: avformat.h:1394
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:206
int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags)
Set the given entry in *pm, overwriting an existing entry.
Definition: dict.c:70
int nb_index_entries
Definition: avformat.h:1106
#define AV_WB32(p, v)
Definition: intreadwrite.h:419
int frames_per_packet
frames in a packet, or 0 if variable
Definition: cafdec.c:41
static void read_info_chunk(AVFormatContext *s, int64_t size)
Read information chunk.
Definition: cafdec.c:221
static enum AVCodecID ff_mov_get_lpcm_codec_id(int bps, int flags)
Compute codec id for &#39;lpcm&#39; tag.
Definition: isom.h:372
This structure contains the data a format has to probe a file.
Definition: avformat.h:441
static int read_pakt_chunk(AVFormatContext *s, int64_t size)
Read packet table chunk.
Definition: cafdec.c:185
#define flags(name, subs,...)
Definition: cbs_av1.c:564
static int read_probe(const AVProbeData *pd)
Definition: jvdec.c:55
int64_t duration
Decoding: duration of the stream, in stream time base.
Definition: avformat.h:924
int sample_rate
Audio only.
Definition: avcodec.h:4146
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:453
Main libavformat public API header.
int64_t start_time
Decoding: pts of the first frame of the stream in presentation order, in stream time base...
Definition: avformat.h:914
int ff_get_extradata(AVFormatContext *s, AVCodecParameters *par, AVIOContext *pb, int size)
Allocate extradata with additional AV_INPUT_BUFFER_PADDING_SIZE at end which is always set to 0 and f...
Definition: utils.c:3341
int64_t nb_frames
number of frames in this stream if known or 0
Definition: avformat.h:926
#define ALAC_HEADER
#define MKBETAG(a, b, c, d)
Definition: common.h:367
#define AV_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding...
Definition: avcodec.h:808
void * priv_data
Format private data.
Definition: avformat.h:1380
int bits_per_coded_sample
The number of bits per sample in the codedwords.
Definition: avcodec.h:4078
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: avcodec.h:4050
int channels
Audio only.
Definition: avcodec.h:4142
int64_t dts
Decompression timestamp in AVStream->time_base units; the time at which the packet is decompressed...
Definition: avcodec.h:1532
static int probe(const AVProbeData *p)
Definition: cafdec.c:51
#define av_freep(p)
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:649
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1022
int avio_get_str(AVIOContext *pb, int maxlen, char *buf, int buflen)
Read a string from pb into buf.
Definition: aviobuf.c:877
int avio_feof(AVIOContext *s)
Similar to feof() but also returns nonzero on read errors.
Definition: aviobuf.c:356
uint32_t codec_tag
Additional information about the codec (corresponds to the AVI FOURCC).
Definition: avcodec.h:4040
static int read_desc_chunk(AVFormatContext *s)
Read audio description chunk.
Definition: cafdec.c:59
int stream_index
Definition: avcodec.h:1535
const AVCodecTag ff_codec_caf_tags[]
Known codec tags for CAF.
Definition: caf.c:34
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 they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Frame references ownership and permissions
#define MKTAG(a, b, c, d)
Definition: common.h:366
This structure stores compressed data.
Definition: avcodec.h:1510
int64_t packet_cnt
packet counter
Definition: cafdec.c:44
int64_t frame_cnt
frame counter
Definition: cafdec.c:45
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:1526