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avformat.h
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1 /*
2  * copyright (c) 2001 Fabrice Bellard
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 #ifndef AVFORMAT_AVFORMAT_H
22 #define AVFORMAT_AVFORMAT_H
23 
24 /**
25  * @file
26  * @ingroup libavf
27  * Main libavformat public API header
28  */
29 
30 /**
31  * @defgroup libavf I/O and Muxing/Demuxing Library
32  * @{
33  *
34  * Libavformat (lavf) is a library for dealing with various media container
35  * formats. Its main two purposes are demuxing - i.e. splitting a media file
36  * into component streams, and the reverse process of muxing - writing supplied
37  * data in a specified container format. It also has an @ref lavf_io
38  * "I/O module" which supports a number of protocols for accessing the data (e.g.
39  * file, tcp, http and others). Before using lavf, you need to call
40  * av_register_all() to register all compiled muxers, demuxers and protocols.
41  * Unless you are absolutely sure you won't use libavformat's network
42  * capabilities, you should also call avformat_network_init().
43  *
44  * A supported input format is described by an AVInputFormat struct, conversely
45  * an output format is described by AVOutputFormat. You can iterate over all
46  * registered input/output formats using the av_iformat_next() /
47  * av_oformat_next() functions. The protocols layer is not part of the public
48  * API, so you can only get the names of supported protocols with the
49  * avio_enum_protocols() function.
50  *
51  * Main lavf structure used for both muxing and demuxing is AVFormatContext,
52  * which exports all information about the file being read or written. As with
53  * most Libavformat structures, its size is not part of public ABI, so it cannot be
54  * allocated on stack or directly with av_malloc(). To create an
55  * AVFormatContext, use avformat_alloc_context() (some functions, like
56  * avformat_open_input() might do that for you).
57  *
58  * Most importantly an AVFormatContext contains:
59  * @li the @ref AVFormatContext.iformat "input" or @ref AVFormatContext.oformat
60  * "output" format. It is either autodetected or set by user for input;
61  * always set by user for output.
62  * @li an @ref AVFormatContext.streams "array" of AVStreams, which describe all
63  * elementary streams stored in the file. AVStreams are typically referred to
64  * using their index in this array.
65  * @li an @ref AVFormatContext.pb "I/O context". It is either opened by lavf or
66  * set by user for input, always set by user for output (unless you are dealing
67  * with an AVFMT_NOFILE format).
68  *
69  * @section lavf_options Passing options to (de)muxers
70  * Lavf allows to configure muxers and demuxers using the @ref avoptions
71  * mechanism. Generic (format-independent) libavformat options are provided by
72  * AVFormatContext, they can be examined from a user program by calling
73  * av_opt_next() / av_opt_find() on an allocated AVFormatContext (or its AVClass
74  * from avformat_get_class()). Private (format-specific) options are provided by
75  * AVFormatContext.priv_data if and only if AVInputFormat.priv_class /
76  * AVOutputFormat.priv_class of the corresponding format struct is non-NULL.
77  * Further options may be provided by the @ref AVFormatContext.pb "I/O context",
78  * if its AVClass is non-NULL, and the protocols layer. See the discussion on
79  * nesting in @ref avoptions documentation to learn how to access those.
80  *
81  * @defgroup lavf_decoding Demuxing
82  * @{
83  * Demuxers read a media file and split it into chunks of data (@em packets). A
84  * @ref AVPacket "packet" contains one or more encoded frames which belongs to a
85  * single elementary stream. In the lavf API this process is represented by the
86  * avformat_open_input() function for opening a file, av_read_frame() for
87  * reading a single packet and finally avformat_close_input(), which does the
88  * cleanup.
89  *
90  * @section lavf_decoding_open Opening a media file
91  * The minimum information required to open a file is its URL or filename, which
92  * is passed to avformat_open_input(), as in the following code:
93  * @code
94  * const char *url = "in.mp3";
95  * AVFormatContext *s = NULL;
96  * int ret = avformat_open_input(&s, url, NULL, NULL);
97  * if (ret < 0)
98  * abort();
99  * @endcode
100  * The above code attempts to allocate an AVFormatContext, open the
101  * specified file (autodetecting the format) and read the header, exporting the
102  * information stored there into s. Some formats do not have a header or do not
103  * store enough information there, so it is recommended that you call the
104  * avformat_find_stream_info() function which tries to read and decode a few
105  * frames to find missing information.
106  *
107  * In some cases you might want to preallocate an AVFormatContext yourself with
108  * avformat_alloc_context() and do some tweaking on it before passing it to
109  * avformat_open_input(). One such case is when you want to use custom functions
110  * for reading input data instead of lavf internal I/O layer.
111  * To do that, create your own AVIOContext with avio_alloc_context(), passing
112  * your reading callbacks to it. Then set the @em pb field of your
113  * AVFormatContext to newly created AVIOContext.
114  *
115  * Since the format of the opened file is in general not known until after
116  * avformat_open_input() has returned, it is not possible to set demuxer private
117  * options on a preallocated context. Instead, the options should be passed to
118  * avformat_open_input() wrapped in an AVDictionary:
119  * @code
120  * AVDictionary *options = NULL;
121  * av_dict_set(&options, "video_size", "640x480", 0);
122  * av_dict_set(&options, "pixel_format", "rgb24", 0);
123  *
124  * if (avformat_open_input(&s, url, NULL, &options) < 0)
125  * abort();
126  * av_dict_free(&options);
127  * @endcode
128  * This code passes the private options 'video_size' and 'pixel_format' to the
129  * demuxer. They would be necessary for e.g. the rawvideo demuxer, since it
130  * cannot know how to interpret raw video data otherwise. If the format turns
131  * out to be something different than raw video, those options will not be
132  * recognized by the demuxer and therefore will not be applied. Such unrecognized
133  * options are then returned in the options dictionary (recognized options are
134  * consumed). The calling program can handle such unrecognized options as it
135  * wishes, e.g.
136  * @code
137  * AVDictionaryEntry *e;
138  * if (e = av_dict_get(options, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
139  * fprintf(stderr, "Option %s not recognized by the demuxer.\n", e->key);
140  * abort();
141  * }
142  * @endcode
143  *
144  * After you have finished reading the file, you must close it with
145  * avformat_close_input(). It will free everything associated with the file.
146  *
147  * @section lavf_decoding_read Reading from an opened file
148  * Reading data from an opened AVFormatContext is done by repeatedly calling
149  * av_read_frame() on it. Each call, if successful, will return an AVPacket
150  * containing encoded data for one AVStream, identified by
151  * AVPacket.stream_index. This packet may be passed straight into the libavcodec
152  * decoding functions avcodec_decode_video2(), avcodec_decode_audio4() or
153  * avcodec_decode_subtitle2() if the caller wishes to decode the data.
154  *
155  * AVPacket.pts, AVPacket.dts and AVPacket.duration timing information will be
156  * set if known. They may also be unset (i.e. AV_NOPTS_VALUE for
157  * pts/dts, 0 for duration) if the stream does not provide them. The timing
158  * information will be in AVStream.time_base units, i.e. it has to be
159  * multiplied by the timebase to convert them to seconds.
160  *
161  * If AVPacket.destruct is set on the returned packet, then the packet is
162  * allocated dynamically and the user may keep it indefinitely.
163  * Otherwise, if AVPacket.destruct is NULL, the packet data is backed by a
164  * static storage somewhere inside the demuxer and the packet is only valid
165  * until the next av_read_frame() call or closing the file. If the caller
166  * requires a longer lifetime, av_dup_packet() will make an av_malloc()ed copy
167  * of it.
168  * In both cases, the packet must be freed with av_free_packet() when it is no
169  * longer needed.
170  *
171  * @section lavf_decoding_seek Seeking
172  * @}
173  *
174  * @defgroup lavf_encoding Muxing
175  * @{
176  * @}
177  *
178  * @defgroup lavf_io I/O Read/Write
179  * @{
180  * @}
181  *
182  * @defgroup lavf_codec Demuxers
183  * @{
184  * @defgroup lavf_codec_native Native Demuxers
185  * @{
186  * @}
187  * @defgroup lavf_codec_wrappers External library wrappers
188  * @{
189  * @}
190  * @}
191  * @defgroup lavf_protos I/O Protocols
192  * @{
193  * @}
194  * @defgroup lavf_internal Internal
195  * @{
196  * @}
197  * @}
198  *
199  */
200 
201 #include <time.h>
202 #include <stdio.h> /* FILE */
203 #include "libavcodec/avcodec.h"
204 #include "libavutil/dict.h"
205 #include "libavutil/log.h"
206 
207 #include "avio.h"
208 #include "libavformat/version.h"
209 
210 #if FF_API_AV_GETTIME
211 #include "libavutil/time.h"
212 #endif
213 
214 struct AVFormatContext;
215 
216 
217 /**
218  * @defgroup metadata_api Public Metadata API
219  * @{
220  * @ingroup libavf
221  * The metadata API allows libavformat to export metadata tags to a client
222  * application when demuxing. Conversely it allows a client application to
223  * set metadata when muxing.
224  *
225  * Metadata is exported or set as pairs of key/value strings in the 'metadata'
226  * fields of the AVFormatContext, AVStream, AVChapter and AVProgram structs
227  * using the @ref lavu_dict "AVDictionary" API. Like all strings in FFmpeg,
228  * metadata is assumed to be UTF-8 encoded Unicode. Note that metadata
229  * exported by demuxers isn't checked to be valid UTF-8 in most cases.
230  *
231  * Important concepts to keep in mind:
232  * - Keys are unique; there can never be 2 tags with the same key. This is
233  * also meant semantically, i.e., a demuxer should not knowingly produce
234  * several keys that are literally different but semantically identical.
235  * E.g., key=Author5, key=Author6. In this example, all authors must be
236  * placed in the same tag.
237  * - Metadata is flat, not hierarchical; there are no subtags. If you
238  * want to store, e.g., the email address of the child of producer Alice
239  * and actor Bob, that could have key=alice_and_bobs_childs_email_address.
240  * - Several modifiers can be applied to the tag name. This is done by
241  * appending a dash character ('-') and the modifier name in the order
242  * they appear in the list below -- e.g. foo-eng-sort, not foo-sort-eng.
243  * - language -- a tag whose value is localized for a particular language
244  * is appended with the ISO 639-2/B 3-letter language code.
245  * For example: Author-ger=Michael, Author-eng=Mike
246  * The original/default language is in the unqualified "Author" tag.
247  * A demuxer should set a default if it sets any translated tag.
248  * - sorting -- a modified version of a tag that should be used for
249  * sorting will have '-sort' appended. E.g. artist="The Beatles",
250  * artist-sort="Beatles, The".
251  *
252  * - Demuxers attempt to export metadata in a generic format, however tags
253  * with no generic equivalents are left as they are stored in the container.
254  * Follows a list of generic tag names:
255  *
256  @verbatim
257  album -- name of the set this work belongs to
258  album_artist -- main creator of the set/album, if different from artist.
259  e.g. "Various Artists" for compilation albums.
260  artist -- main creator of the work
261  comment -- any additional description of the file.
262  composer -- who composed the work, if different from artist.
263  copyright -- name of copyright holder.
264  creation_time-- date when the file was created, preferably in ISO 8601.
265  date -- date when the work was created, preferably in ISO 8601.
266  disc -- number of a subset, e.g. disc in a multi-disc collection.
267  encoder -- name/settings of the software/hardware that produced the file.
268  encoded_by -- person/group who created the file.
269  filename -- original name of the file.
270  genre -- <self-evident>.
271  language -- main language in which the work is performed, preferably
272  in ISO 639-2 format. Multiple languages can be specified by
273  separating them with commas.
274  performer -- artist who performed the work, if different from artist.
275  E.g for "Also sprach Zarathustra", artist would be "Richard
276  Strauss" and performer "London Philharmonic Orchestra".
277  publisher -- name of the label/publisher.
278  service_name -- name of the service in broadcasting (channel name).
279  service_provider -- name of the service provider in broadcasting.
280  title -- name of the work.
281  track -- number of this work in the set, can be in form current/total.
282  variant_bitrate -- the total bitrate of the bitrate variant that the current stream is part of
283  @endverbatim
284  *
285  * Look in the examples section for an application example how to use the Metadata API.
286  *
287  * @}
288  */
289 
290 /* packet functions */
291 
292 
293 /**
294  * Allocate and read the payload of a packet and initialize its
295  * fields with default values.
296  *
297  * @param pkt packet
298  * @param size desired payload size
299  * @return >0 (read size) if OK, AVERROR_xxx otherwise
300  */
301 int av_get_packet(AVIOContext *s, AVPacket *pkt, int size);
302 
303 
304 /**
305  * Read data and append it to the current content of the AVPacket.
306  * If pkt->size is 0 this is identical to av_get_packet.
307  * Note that this uses av_grow_packet and thus involves a realloc
308  * which is inefficient. Thus this function should only be used
309  * when there is no reasonable way to know (an upper bound of)
310  * the final size.
311  *
312  * @param pkt packet
313  * @param size amount of data to read
314  * @return >0 (read size) if OK, AVERROR_xxx otherwise, previous data
315  * will not be lost even if an error occurs.
316  */
318 
319 /*************************************************/
320 /* fractional numbers for exact pts handling */
321 
322 /**
323  * The exact value of the fractional number is: 'val + num / den'.
324  * num is assumed to be 0 <= num < den.
325  */
326 typedef struct AVFrac {
327  int64_t val, num, den;
328 } AVFrac;
329 
330 /*************************************************/
331 /* input/output formats */
332 
333 struct AVCodecTag;
334 
335 /**
336  * This structure contains the data a format has to probe a file.
337  */
338 typedef struct AVProbeData {
339  const char *filename;
340  unsigned char *buf; /**< Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero. */
341  int buf_size; /**< Size of buf except extra allocated bytes */
342 } AVProbeData;
343 
344 #define AVPROBE_SCORE_MAX 100 ///< maximum score, half of that is used for file-extension-based detection
345 #define AVPROBE_SCORE_RETRY (AVPROBE_SCORE_MAX/4)
346 #define AVPROBE_PADDING_SIZE 32 ///< extra allocated bytes at the end of the probe buffer
347 
348 /// Demuxer will use avio_open, no opened file should be provided by the caller.
349 #define AVFMT_NOFILE 0x0001
350 #define AVFMT_NEEDNUMBER 0x0002 /**< Needs '%d' in filename. */
351 #define AVFMT_SHOW_IDS 0x0008 /**< Show format stream IDs numbers. */
352 #define AVFMT_RAWPICTURE 0x0020 /**< Format wants AVPicture structure for
353  raw picture data. */
354 #define AVFMT_GLOBALHEADER 0x0040 /**< Format wants global header. */
355 #define AVFMT_NOTIMESTAMPS 0x0080 /**< Format does not need / have any timestamps. */
356 #define AVFMT_GENERIC_INDEX 0x0100 /**< Use generic index building code. */
357 #define AVFMT_TS_DISCONT 0x0200 /**< Format allows timestamp discontinuities. Note, muxers always require valid (monotone) timestamps */
358 #define AVFMT_VARIABLE_FPS 0x0400 /**< Format allows variable fps. */
359 #define AVFMT_NODIMENSIONS 0x0800 /**< Format does not need width/height */
360 #define AVFMT_NOSTREAMS 0x1000 /**< Format does not require any streams */
361 #define AVFMT_NOBINSEARCH 0x2000 /**< Format does not allow to fallback to binary search via read_timestamp */
362 #define AVFMT_NOGENSEARCH 0x4000 /**< Format does not allow to fallback to generic search */
363 #define AVFMT_NO_BYTE_SEEK 0x8000 /**< Format does not allow seeking by bytes */
364 #define AVFMT_ALLOW_FLUSH 0x10000 /**< Format allows flushing. If not set, the muxer will not receive a NULL packet in the write_packet function. */
365 #if LIBAVFORMAT_VERSION_MAJOR <= 54
366 #define AVFMT_TS_NONSTRICT 0x8020000 //we try to be compatible to the ABIs of ffmpeg and major forks
367 #else
368 #define AVFMT_TS_NONSTRICT 0x20000
369 #endif
370  /**< Format does not require strictly
371  increasing timestamps, but they must
372  still be monotonic */
373 
374 #define AVFMT_SEEK_TO_PTS 0x4000000 /**< Seeking is based on PTS */
375 
376 /**
377  * @addtogroup lavf_encoding
378  * @{
379  */
380 typedef struct AVOutputFormat {
381  const char *name;
382  /**
383  * Descriptive name for the format, meant to be more human-readable
384  * than name. You should use the NULL_IF_CONFIG_SMALL() macro
385  * to define it.
386  */
387  const char *long_name;
388  const char *mime_type;
389  const char *extensions; /**< comma-separated filename extensions */
390  /* output support */
391  enum AVCodecID audio_codec; /**< default audio codec */
392  enum AVCodecID video_codec; /**< default video codec */
393  enum AVCodecID subtitle_codec; /**< default subtitle codec */
394  /**
395  * can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER, AVFMT_RAWPICTURE,
396  * AVFMT_GLOBALHEADER, AVFMT_NOTIMESTAMPS, AVFMT_VARIABLE_FPS,
397  * AVFMT_NODIMENSIONS, AVFMT_NOSTREAMS, AVFMT_ALLOW_FLUSH,
398  * AVFMT_TS_NONSTRICT
399  */
400  int flags;
401 
402  /**
403  * List of supported codec_id-codec_tag pairs, ordered by "better
404  * choice first". The arrays are all terminated by AV_CODEC_ID_NONE.
405  */
406  const struct AVCodecTag * const *codec_tag;
407 
408 
409  const AVClass *priv_class; ///< AVClass for the private context
410 
411  /*****************************************************************
412  * No fields below this line are part of the public API. They
413  * may not be used outside of libavformat and can be changed and
414  * removed at will.
415  * New public fields should be added right above.
416  *****************************************************************
417  */
419  /**
420  * size of private data so that it can be allocated in the wrapper
421  */
423 
424  int (*write_header)(struct AVFormatContext *);
425  /**
426  * Write a packet. If AVFMT_ALLOW_FLUSH is set in flags,
427  * pkt can be NULL in order to flush data buffered in the muxer.
428  * When flushing, return 0 if there still is more data to flush,
429  * or 1 if everything was flushed and there is no more buffered
430  * data.
431  */
433  int (*write_trailer)(struct AVFormatContext *);
434  /**
435  * Currently only used to set pixel format if not YUV420P.
436  */
438  AVPacket *in, int flush);
439  /**
440  * Test if the given codec can be stored in this container.
441  *
442  * @return 1 if the codec is supported, 0 if it is not.
443  * A negative number if unknown.
444  * MKTAG('A', 'P', 'I', 'C') if the codec is only supported as AV_DISPOSITION_ATTACHED_PIC
445  */
446  int (*query_codec)(enum AVCodecID id, int std_compliance);
447 
448  void (*get_output_timestamp)(struct AVFormatContext *s, int stream,
449  int64_t *dts, int64_t *wall);
451 /**
452  * @}
453  */
454 
455 /**
456  * @addtogroup lavf_decoding
457  * @{
458  */
459 typedef struct AVInputFormat {
460  /**
461  * A comma separated list of short names for the format. New names
462  * may be appended with a minor bump.
463  */
464  const char *name;
465 
466  /**
467  * Descriptive name for the format, meant to be more human-readable
468  * than name. You should use the NULL_IF_CONFIG_SMALL() macro
469  * to define it.
470  */
471  const char *long_name;
472 
473  /**
474  * Can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER, AVFMT_SHOW_IDS,
475  * AVFMT_GENERIC_INDEX, AVFMT_TS_DISCONT, AVFMT_NOBINSEARCH,
476  * AVFMT_NOGENSEARCH, AVFMT_NO_BYTE_SEEK, AVFMT_SEEK_TO_PTS.
477  */
478  int flags;
479 
480  /**
481  * If extensions are defined, then no probe is done. You should
482  * usually not use extension format guessing because it is not
483  * reliable enough
484  */
485  const char *extensions;
486 
487  const struct AVCodecTag * const *codec_tag;
488 
489  const AVClass *priv_class; ///< AVClass for the private context
490 
491  /*****************************************************************
492  * No fields below this line are part of the public API. They
493  * may not be used outside of libavformat and can be changed and
494  * removed at will.
495  * New public fields should be added right above.
496  *****************************************************************
497  */
499 
500  /**
501  * Raw demuxers store their codec ID here.
502  */
504 
505  /**
506  * Size of private data so that it can be allocated in the wrapper.
507  */
509 
510  /**
511  * Tell if a given file has a chance of being parsed as this format.
512  * The buffer provided is guaranteed to be AVPROBE_PADDING_SIZE bytes
513  * big so you do not have to check for that unless you need more.
514  */
516 
517  /**
518  * Read the format header and initialize the AVFormatContext
519  * structure. Return 0 if OK. Only used in raw format right
520  * now. 'avformat_new_stream' should be called to create new streams.
521  */
522  int (*read_header)(struct AVFormatContext *);
523 
524  /**
525  * Read one packet and put it in 'pkt'. pts and flags are also
526  * set. 'avformat_new_stream' can be called only if the flag
527  * AVFMTCTX_NOHEADER is used and only in the calling thread (not in a
528  * background thread).
529  * @return 0 on success, < 0 on error.
530  * When returning an error, pkt must not have been allocated
531  * or must be freed before returning
532  */
534 
535  /**
536  * Close the stream. The AVFormatContext and AVStreams are not
537  * freed by this function
538  */
539  int (*read_close)(struct AVFormatContext *);
540 
541  /**
542  * Seek to a given timestamp relative to the frames in
543  * stream component stream_index.
544  * @param stream_index Must not be -1.
545  * @param flags Selects which direction should be preferred if no exact
546  * match is available.
547  * @return >= 0 on success (but not necessarily the new offset)
548  */
549  int (*read_seek)(struct AVFormatContext *,
550  int stream_index, int64_t timestamp, int flags);
551 
552  /**
553  * Get the next timestamp in stream[stream_index].time_base units.
554  * @return the timestamp or AV_NOPTS_VALUE if an error occurred
555  */
556  int64_t (*read_timestamp)(struct AVFormatContext *s, int stream_index,
557  int64_t *pos, int64_t pos_limit);
558 
559  /**
560  * Start/resume playing - only meaningful if using a network-based format
561  * (RTSP).
562  */
563  int (*read_play)(struct AVFormatContext *);
564 
565  /**
566  * Pause playing - only meaningful if using a network-based format
567  * (RTSP).
568  */
569  int (*read_pause)(struct AVFormatContext *);
570 
571  /**
572  * Seek to timestamp ts.
573  * Seeking will be done so that the point from which all active streams
574  * can be presented successfully will be closest to ts and within min/max_ts.
575  * Active streams are all streams that have AVStream.discard < AVDISCARD_ALL.
576  */
577  int (*read_seek2)(struct AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags);
578 } AVInputFormat;
579 /**
580  * @}
581  */
582 
585  AVSTREAM_PARSE_FULL, /**< full parsing and repack */
586  AVSTREAM_PARSE_HEADERS, /**< Only parse headers, do not repack. */
587  AVSTREAM_PARSE_TIMESTAMPS, /**< full parsing and interpolation of timestamps for frames not starting on a packet boundary */
588  AVSTREAM_PARSE_FULL_ONCE, /**< full parsing and repack of the first frame only, only implemented for H.264 currently */
589  AVSTREAM_PARSE_FULL_RAW=MKTAG(0,'R','A','W'), /**< full parsing and repack with timestamp and position generation by parser for raw
590  this assumes that each packet in the file contains no demuxer level headers and
591  just codec level data, otherwise position generation would fail */
592 };
593 
594 typedef struct AVIndexEntry {
595  int64_t pos;
596  int64_t timestamp; /**<
597  * Timestamp in AVStream.time_base units, preferably the time from which on correctly decoded frames are available
598  * when seeking to this entry. That means preferable PTS on keyframe based formats.
599  * But demuxers can choose to store a different timestamp, if it is more convenient for the implementation or nothing better
600  * is known
601  */
602 #define AVINDEX_KEYFRAME 0x0001
603  int flags:2;
604  int size:30; //Yeah, trying to keep the size of this small to reduce memory requirements (it is 24 vs. 32 bytes due to possible 8-byte alignment).
605  int min_distance; /**< Minimum distance between this and the previous keyframe, used to avoid unneeded searching. */
606 } AVIndexEntry;
607 
608 #define AV_DISPOSITION_DEFAULT 0x0001
609 #define AV_DISPOSITION_DUB 0x0002
610 #define AV_DISPOSITION_ORIGINAL 0x0004
611 #define AV_DISPOSITION_COMMENT 0x0008
612 #define AV_DISPOSITION_LYRICS 0x0010
613 #define AV_DISPOSITION_KARAOKE 0x0020
614 
615 /**
616  * Track should be used during playback by default.
617  * Useful for subtitle track that should be displayed
618  * even when user did not explicitly ask for subtitles.
619  */
620 #define AV_DISPOSITION_FORCED 0x0040
621 #define AV_DISPOSITION_HEARING_IMPAIRED 0x0080 /**< stream for hearing impaired audiences */
622 #define AV_DISPOSITION_VISUAL_IMPAIRED 0x0100 /**< stream for visual impaired audiences */
623 #define AV_DISPOSITION_CLEAN_EFFECTS 0x0200 /**< stream without voice */
624 /**
625  * The stream is stored in the file as an attached picture/"cover art" (e.g.
626  * APIC frame in ID3v2). The single packet associated with it will be returned
627  * among the first few packets read from the file unless seeking takes place.
628  * It can also be accessed at any time in AVStream.attached_pic.
629  */
630 #define AV_DISPOSITION_ATTACHED_PIC 0x0400
631 
632 /**
633  * Options for behavior on timestamp wrap detection.
634  */
635 #define AV_PTS_WRAP_IGNORE 0 ///< ignore the wrap
636 #define AV_PTS_WRAP_ADD_OFFSET 1 ///< add the format specific offset on wrap detection
637 #define AV_PTS_WRAP_SUB_OFFSET -1 ///< subtract the format specific offset on wrap detection
638 
639 /**
640  * Stream structure.
641  * New fields can be added to the end with minor version bumps.
642  * Removal, reordering and changes to existing fields require a major
643  * version bump.
644  * sizeof(AVStream) must not be used outside libav*.
645  */
646 typedef struct AVStream {
647  int index; /**< stream index in AVFormatContext */
648  /**
649  * Format-specific stream ID.
650  * decoding: set by libavformat
651  * encoding: set by the user, replaced by libavformat if left unset
652  */
653  int id;
654  /**
655  * Codec context associated with this stream. Allocated and freed by
656  * libavformat.
657  *
658  * - decoding: The demuxer exports codec information stored in the headers
659  * here.
660  * - encoding: The user sets codec information, the muxer writes it to the
661  * output. Mandatory fields as specified in AVCodecContext
662  * documentation must be set even if this AVCodecContext is
663  * not actually used for encoding.
664  */
666 #if FF_API_R_FRAME_RATE
667  /**
668  * Real base framerate of the stream.
669  * This is the lowest framerate with which all timestamps can be
670  * represented accurately (it is the least common multiple of all
671  * framerates in the stream). Note, this value is just a guess!
672  * For example, if the time base is 1/90000 and all frames have either
673  * approximately 3600 or 1800 timer ticks, then r_frame_rate will be 50/1.
674  */
675  AVRational r_frame_rate;
676 #endif
677  void *priv_data;
678 
679  /**
680  * encoding: pts generation when outputting stream
681  */
682  struct AVFrac pts;
683 
684  /**
685  * This is the fundamental unit of time (in seconds) in terms
686  * of which frame timestamps are represented.
687  *
688  * decoding: set by libavformat
689  * encoding: set by libavformat in avformat_write_header. The muxer may use the
690  * user-provided value of @ref AVCodecContext.time_base "codec->time_base"
691  * as a hint.
692  */
694 
695  /**
696  * Decoding: pts of the first frame of the stream in presentation order, in stream time base.
697  * Only set this if you are absolutely 100% sure that the value you set
698  * it to really is the pts of the first frame.
699  * This may be undefined (AV_NOPTS_VALUE).
700  * @note The ASF header does NOT contain a correct start_time the ASF
701  * demuxer must NOT set this.
702  */
703  int64_t start_time;
704 
705  /**
706  * Decoding: duration of the stream, in stream time base.
707  * If a source file does not specify a duration, but does specify
708  * a bitrate, this value will be estimated from bitrate and file size.
709  */
710  int64_t duration;
711 
712  int64_t nb_frames; ///< number of frames in this stream if known or 0
713 
714  int disposition; /**< AV_DISPOSITION_* bit field */
715 
716  enum AVDiscard discard; ///< Selects which packets can be discarded at will and do not need to be demuxed.
717 
718  /**
719  * sample aspect ratio (0 if unknown)
720  * - encoding: Set by user.
721  * - decoding: Set by libavformat.
722  */
724 
726 
727  /**
728  * Average framerate
729  */
731 
732  /**
733  * For streams with AV_DISPOSITION_ATTACHED_PIC disposition, this packet
734  * will contain the attached picture.
735  *
736  * decoding: set by libavformat, must not be modified by the caller.
737  * encoding: unused
738  */
740 
741  /*****************************************************************
742  * All fields below this line are not part of the public API. They
743  * may not be used outside of libavformat and can be changed and
744  * removed at will.
745  * New public fields should be added right above.
746  *****************************************************************
747  */
748 
749  /**
750  * Stream information used internally by av_find_stream_info()
751  */
752 #define MAX_STD_TIMEBASES (60*12+6)
753  struct {
754  int64_t last_dts;
755  int64_t duration_gcd;
761 
762  int64_t last_duration;
763 
764  /**
765  * Those are used for average framerate estimation.
766  */
767  int64_t fps_first_dts;
769  int64_t fps_last_dts;
771 
772  } *info;
773 
774  int pts_wrap_bits; /**< number of bits in pts (used for wrapping control) */
775 
776  // Timestamp generation support:
777  /**
778  * Timestamp corresponding to the last dts sync point.
779  *
780  * Initialized when AVCodecParserContext.dts_sync_point >= 0 and
781  * a DTS is received from the underlying container. Otherwise set to
782  * AV_NOPTS_VALUE by default.
783  */
784  int64_t reference_dts;
785  int64_t first_dts;
786  int64_t cur_dts;
787  int64_t last_IP_pts;
789 
790  /**
791  * Number of packets to buffer for codec probing
792  */
793 #define MAX_PROBE_PACKETS 2500
795 
796  /**
797  * Number of frames that have been demuxed during av_find_stream_info()
798  */
800 
801  /**
802  * Stream Identifier
803  * This is the MPEG-TS stream identifier +1
804  * 0 means unknown
805  */
807 
810 
811  /* av_read_frame() support */
814 
815  /**
816  * last packet in packet_buffer for this stream when muxing.
817  */
820 #define MAX_REORDER_DELAY 16
822 
823  AVIndexEntry *index_entries; /**< Only used if the format does not
824  support seeking natively. */
827 
828  /**
829  * stream probing state
830  * -1 -> probing finished
831  * 0 -> no probing requested
832  * rest -> perform probing with request_probe being the minimum score to accept.
833  * NOT PART OF PUBLIC API
834  */
836  /**
837  * Indicates that everything up to the next keyframe
838  * should be discarded.
839  */
841 
842  /**
843  * Number of samples to skip at the start of the frame decoded from the next packet.
844  */
846 
847  /**
848  * Number of internally decoded frames, used internally in libavformat, do not access
849  * its lifetime differs from info which is why it is not in that structure.
850  */
852 
853  /**
854  * Timestamp offset added to timestamps before muxing
855  * NOT PART OF PUBLIC API
856  */
857  int64_t mux_ts_offset;
858 
859  /**
860  * Internal data to check for wrapping of the time stamp
861  */
863 
864  /**
865  * Options for behavior, when a wrap is detected.
866  *
867  * Defined by AV_PTS_WRAP_ values.
868  *
869  * If correction is enabled, there are two possibilities:
870  * If the first time stamp is near the wrap point, the wrap offset
871  * will be subtracted, which will create negative time stamps.
872  * Otherwise the offset will be added.
873  */
875 
876 } AVStream;
877 
878 #define AV_PROGRAM_RUNNING 1
879 
880 /**
881  * New fields can be added to the end with minor version bumps.
882  * Removal, reordering and changes to existing fields require a major
883  * version bump.
884  * sizeof(AVProgram) must not be used outside libav*.
885  */
886 typedef struct AVProgram {
887  int id;
888  int flags;
889  enum AVDiscard discard; ///< selects which program to discard and which to feed to the caller
890  unsigned int *stream_index;
891  unsigned int nb_stream_indexes;
893 
895  int pmt_pid;
896  int pcr_pid;
897 
898  /*****************************************************************
899  * All fields below this line are not part of the public API. They
900  * may not be used outside of libavformat and can be changed and
901  * removed at will.
902  * New public fields should be added right above.
903  *****************************************************************
904  */
905  int64_t start_time;
906  int64_t end_time;
907 
908  int64_t pts_wrap_reference; ///< reference dts for wrap detection
909  int pts_wrap_behavior; ///< behavior on wrap detection
910 } AVProgram;
911 
912 #define AVFMTCTX_NOHEADER 0x0001 /**< signal that no header is present
913  (streams are added dynamically) */
914 
915 typedef struct AVChapter {
916  int id; ///< unique ID to identify the chapter
917  AVRational time_base; ///< time base in which the start/end timestamps are specified
918  int64_t start, end; ///< chapter start/end time in time_base units
920 } AVChapter;
921 
922 
923 /**
924  * The duration of a video can be estimated through various ways, and this enum can be used
925  * to know how the duration was estimated.
926  */
928  AVFMT_DURATION_FROM_PTS, ///< Duration accurately estimated from PTSes
929  AVFMT_DURATION_FROM_STREAM, ///< Duration estimated from a stream with a known duration
930  AVFMT_DURATION_FROM_BITRATE ///< Duration estimated from bitrate (less accurate)
931 };
932 
933 /**
934  * Format I/O context.
935  * New fields can be added to the end with minor version bumps.
936  * Removal, reordering and changes to existing fields require a major
937  * version bump.
938  * sizeof(AVFormatContext) must not be used outside libav*, use
939  * avformat_alloc_context() to create an AVFormatContext.
940  */
941 typedef struct AVFormatContext {
942  /**
943  * A class for logging and AVOptions. Set by avformat_alloc_context().
944  * Exports (de)muxer private options if they exist.
945  */
947 
948  /**
949  * Can only be iformat or oformat, not both at the same time.
950  *
951  * decoding: set by avformat_open_input().
952  * encoding: set by the user.
953  */
956 
957  /**
958  * Format private data. This is an AVOptions-enabled struct
959  * if and only if iformat/oformat.priv_class is not NULL.
960  */
961  void *priv_data;
962 
963  /**
964  * I/O context.
965  *
966  * decoding: either set by the user before avformat_open_input() (then
967  * the user must close it manually) or set by avformat_open_input().
968  * encoding: set by the user.
969  *
970  * Do NOT set this field if AVFMT_NOFILE flag is set in
971  * iformat/oformat.flags. In such a case, the (de)muxer will handle
972  * I/O in some other way and this field will be NULL.
973  */
975 
976  /* stream info */
977  int ctx_flags; /**< Format-specific flags, see AVFMTCTX_xx */
978 
979  /**
980  * A list of all streams in the file. New streams are created with
981  * avformat_new_stream().
982  *
983  * decoding: streams are created by libavformat in avformat_open_input().
984  * If AVFMTCTX_NOHEADER is set in ctx_flags, then new streams may also
985  * appear in av_read_frame().
986  * encoding: streams are created by the user before avformat_write_header().
987  */
988  unsigned int nb_streams;
990 
991  char filename[1024]; /**< input or output filename */
992 
993  /**
994  * Decoding: position of the first frame of the component, in
995  * AV_TIME_BASE fractional seconds. NEVER set this value directly:
996  * It is deduced from the AVStream values.
997  */
998  int64_t start_time;
999 
1000  /**
1001  * Decoding: duration of the stream, in AV_TIME_BASE fractional
1002  * seconds. Only set this value if you know none of the individual stream
1003  * durations and also do not set any of them. This is deduced from the
1004  * AVStream values if not set.
1005  */
1006  int64_t duration;
1007 
1008  /**
1009  * Decoding: total stream bitrate in bit/s, 0 if not
1010  * available. Never set it directly if the file_size and the
1011  * duration are known as FFmpeg can compute it automatically.
1012  */
1014 
1015  unsigned int packet_size;
1017 
1018  int flags;
1019 #define AVFMT_FLAG_GENPTS 0x0001 ///< Generate missing pts even if it requires parsing future frames.
1020 #define AVFMT_FLAG_IGNIDX 0x0002 ///< Ignore index.
1021 #define AVFMT_FLAG_NONBLOCK 0x0004 ///< Do not block when reading packets from input.
1022 #define AVFMT_FLAG_IGNDTS 0x0008 ///< Ignore DTS on frames that contain both DTS & PTS
1023 #define AVFMT_FLAG_NOFILLIN 0x0010 ///< Do not infer any values from other values, just return what is stored in the container
1024 #define AVFMT_FLAG_NOPARSE 0x0020 ///< Do not use AVParsers, you also must set AVFMT_FLAG_NOFILLIN as the fillin code works on frames and no parsing -> no frames. Also seeking to frames can not work if parsing to find frame boundaries has been disabled
1025 #define AVFMT_FLAG_NOBUFFER 0x0040 ///< Do not buffer frames when possible
1026 #define AVFMT_FLAG_CUSTOM_IO 0x0080 ///< The caller has supplied a custom AVIOContext, don't avio_close() it.
1027 #define AVFMT_FLAG_DISCARD_CORRUPT 0x0100 ///< Discard frames marked corrupted
1028 #define AVFMT_FLAG_MP4A_LATM 0x8000 ///< Enable RTP MP4A-LATM payload
1029 #define AVFMT_FLAG_SORT_DTS 0x10000 ///< try to interleave outputted packets by dts (using this flag can slow demuxing down)
1030 #define AVFMT_FLAG_PRIV_OPT 0x20000 ///< Enable use of private options by delaying codec open (this could be made default once all code is converted)
1031 #define AVFMT_FLAG_KEEP_SIDE_DATA 0x40000 ///< Don't merge side data but keep it separate.
1032 
1033  /**
1034  * decoding: size of data to probe; encoding: unused.
1035  */
1036  unsigned int probesize;
1037 
1038  /**
1039  * decoding: maximum time (in AV_TIME_BASE units) during which the input should
1040  * be analyzed in avformat_find_stream_info().
1041  */
1043 
1044  const uint8_t *key;
1045  int keylen;
1046 
1047  unsigned int nb_programs;
1049 
1050  /**
1051  * Forced video codec_id.
1052  * Demuxing: Set by user.
1053  */
1055 
1056  /**
1057  * Forced audio codec_id.
1058  * Demuxing: Set by user.
1059  */
1061 
1062  /**
1063  * Forced subtitle codec_id.
1064  * Demuxing: Set by user.
1065  */
1067 
1068  /**
1069  * Maximum amount of memory in bytes to use for the index of each stream.
1070  * If the index exceeds this size, entries will be discarded as
1071  * needed to maintain a smaller size. This can lead to slower or less
1072  * accurate seeking (depends on demuxer).
1073  * Demuxers for which a full in-memory index is mandatory will ignore
1074  * this.
1075  * muxing : unused
1076  * demuxing: set by user
1077  */
1078  unsigned int max_index_size;
1079 
1080  /**
1081  * Maximum amount of memory in bytes to use for buffering frames
1082  * obtained from realtime capture devices.
1083  */
1084  unsigned int max_picture_buffer;
1085 
1086  unsigned int nb_chapters;
1088 
1090 
1091  /**
1092  * Start time of the stream in real world time, in microseconds
1093  * since the unix epoch (00:00 1st January 1970). That is, pts=0
1094  * in the stream was captured at this real world time.
1095  * - encoding: Set by user.
1096  * - decoding: Unused.
1097  */
1099 
1100  /**
1101  * decoding: number of frames used to probe fps
1102  */
1104 
1105  /**
1106  * Error recognition; higher values will detect more errors but may
1107  * misdetect some more or less valid parts as errors.
1108  * - encoding: unused
1109  * - decoding: Set by user.
1110  */
1112 
1113  /**
1114  * Custom interrupt callbacks for the I/O layer.
1115  *
1116  * decoding: set by the user before avformat_open_input().
1117  * encoding: set by the user before avformat_write_header()
1118  * (mainly useful for AVFMT_NOFILE formats). The callback
1119  * should also be passed to avio_open2() if it's used to
1120  * open the file.
1121  */
1123 
1124  /**
1125  * Flags to enable debugging.
1126  */
1127  int debug;
1128 #define FF_FDEBUG_TS 0x0001
1129 
1130  /**
1131  * Transport stream id.
1132  * This will be moved into demuxer private options. Thus no API/ABI compatibility
1133  */
1134  int ts_id;
1135 
1136  /**
1137  * Audio preload in microseconds.
1138  * Note, not all formats support this and unpredictable things may happen if it is used when not supported.
1139  * - encoding: Set by user via AVOptions (NO direct access)
1140  * - decoding: unused
1141  */
1143 
1144  /**
1145  * Max chunk time in microseconds.
1146  * Note, not all formats support this and unpredictable things may happen if it is used when not supported.
1147  * - encoding: Set by user via AVOptions (NO direct access)
1148  * - decoding: unused
1149  */
1151 
1152  /**
1153  * Max chunk size in bytes
1154  * Note, not all formats support this and unpredictable things may happen if it is used when not supported.
1155  * - encoding: Set by user via AVOptions (NO direct access)
1156  * - decoding: unused
1157  */
1159 
1160  /**
1161  * forces the use of wallclock timestamps as pts/dts of packets
1162  * This has undefined results in the presence of B frames.
1163  * - encoding: unused
1164  * - decoding: Set by user via AVOptions (NO direct access)
1165  */
1167 
1168  /**
1169  * Avoids negative timestamps during muxing
1170  * 0 -> allow negative timestamps
1171  * 1 -> avoid negative timestamps
1172  * -1 -> choose automatically (default)
1173  * Note, this is only works when interleave_packet_per_dts is in use
1174  * - encoding: Set by user via AVOptions (NO direct access)
1175  * - decoding: unused
1176  */
1178 
1179  /**
1180  * avio flags, used to force AVIO_FLAG_DIRECT.
1181  * - encoding: unused
1182  * - decoding: Set by user via AVOptions (NO direct access)
1183  */
1185 
1186  /**
1187  * The duration field can be estimated through various ways, and this field can be used
1188  * to know how the duration was estimated.
1189  * - encoding: unused
1190  * - decoding: Read by user via AVOptions (NO direct access)
1191  */
1193 
1194  /**
1195  * Skip initial bytes when opening stream
1196  * - encoding: unused
1197  * - decoding: Set by user via AVOptions (NO direct access)
1198  */
1199  unsigned int skip_initial_bytes;
1200 
1201  /**
1202  * Correct single timestamp overflows
1203  * - encoding: unused
1204  * - decoding: Set by user via AVOPtions (NO direct access)
1205  */
1206  unsigned int correct_ts_overflow;
1207 
1208  /**
1209  * Force seeking to any (also non key) frames.
1210  * - encoding: unused
1211  * - decoding: Set by user via AVOPtions (NO direct access)
1212  */
1214 
1215  /*****************************************************************
1216  * All fields below this line are not part of the public API. They
1217  * may not be used outside of libavformat and can be changed and
1218  * removed at will.
1219  * New public fields should be added right above.
1220  *****************************************************************
1221  */
1222 
1223  /**
1224  * This buffer is only needed when packets were already buffered but
1225  * not decoded, for example to get the codec parameters in MPEG
1226  * streams.
1227  */
1230 
1231  /* av_seek_frame() support */
1232  int64_t data_offset; /**< offset of the first packet */
1233 
1234  /**
1235  * Raw packets from the demuxer, prior to parsing and decoding.
1236  * This buffer is used for buffering packets until the codec can
1237  * be identified, as parsing cannot be done without knowing the
1238  * codec.
1239  */
1242  /**
1243  * Packets split by the parser get queued here.
1244  */
1247  /**
1248  * Remaining size available for raw_packet_buffer, in bytes.
1249  */
1250 #define RAW_PACKET_BUFFER_SIZE 2500000
1252 } AVFormatContext;
1253 
1254 /**
1255  * Returns the method used to set ctx->duration.
1256  *
1257  * @return AVFMT_DURATION_FROM_PTS, AVFMT_DURATION_FROM_STREAM, or AVFMT_DURATION_FROM_BITRATE.
1258  */
1260 
1261 typedef struct AVPacketList {
1264 } AVPacketList;
1265 
1266 
1267 /**
1268  * @defgroup lavf_core Core functions
1269  * @ingroup libavf
1270  *
1271  * Functions for querying libavformat capabilities, allocating core structures,
1272  * etc.
1273  * @{
1274  */
1275 
1276 /**
1277  * Return the LIBAVFORMAT_VERSION_INT constant.
1278  */
1279 unsigned avformat_version(void);
1280 
1281 /**
1282  * Return the libavformat build-time configuration.
1283  */
1284 const char *avformat_configuration(void);
1285 
1286 /**
1287  * Return the libavformat license.
1288  */
1289 const char *avformat_license(void);
1290 
1291 /**
1292  * Initialize libavformat and register all the muxers, demuxers and
1293  * protocols. If you do not call this function, then you can select
1294  * exactly which formats you want to support.
1295  *
1296  * @see av_register_input_format()
1297  * @see av_register_output_format()
1298  */
1299 void av_register_all(void);
1300 
1303 
1304 /**
1305  * Do global initialization of network components. This is optional,
1306  * but recommended, since it avoids the overhead of implicitly
1307  * doing the setup for each session.
1308  *
1309  * Calling this function will become mandatory if using network
1310  * protocols at some major version bump.
1311  */
1312 int avformat_network_init(void);
1313 
1314 /**
1315  * Undo the initialization done by avformat_network_init.
1316  */
1317 int avformat_network_deinit(void);
1318 
1319 /**
1320  * If f is NULL, returns the first registered input format,
1321  * if f is non-NULL, returns the next registered input format after f
1322  * or NULL if f is the last one.
1323  */
1325 
1326 /**
1327  * If f is NULL, returns the first registered output format,
1328  * if f is non-NULL, returns the next registered output format after f
1329  * or NULL if f is the last one.
1330  */
1332 
1333 /**
1334  * Allocate an AVFormatContext.
1335  * avformat_free_context() can be used to free the context and everything
1336  * allocated by the framework within it.
1337  */
1339 
1340 /**
1341  * Free an AVFormatContext and all its streams.
1342  * @param s context to free
1343  */
1345 
1346 /**
1347  * Get the AVClass for AVFormatContext. It can be used in combination with
1348  * AV_OPT_SEARCH_FAKE_OBJ for examining options.
1349  *
1350  * @see av_opt_find().
1351  */
1352 const AVClass *avformat_get_class(void);
1353 
1354 /**
1355  * Add a new stream to a media file.
1356  *
1357  * When demuxing, it is called by the demuxer in read_header(). If the
1358  * flag AVFMTCTX_NOHEADER is set in s.ctx_flags, then it may also
1359  * be called in read_packet().
1360  *
1361  * When muxing, should be called by the user before avformat_write_header().
1362  *
1363  * @param c If non-NULL, the AVCodecContext corresponding to the new stream
1364  * will be initialized to use this codec. This is needed for e.g. codec-specific
1365  * defaults to be set, so codec should be provided if it is known.
1366  *
1367  * @return newly created stream or NULL on error.
1368  */
1370 
1372 
1373 /**
1374  * @}
1375  */
1376 
1377 
1378 #if FF_API_PKT_DUMP
1379 attribute_deprecated void av_pkt_dump(FILE *f, AVPacket *pkt, int dump_payload);
1380 attribute_deprecated void av_pkt_dump_log(void *avcl, int level, AVPacket *pkt,
1381  int dump_payload);
1382 #endif
1383 
1384 #if FF_API_ALLOC_OUTPUT_CONTEXT
1385 /**
1386  * @deprecated deprecated in favor of avformat_alloc_output_context2()
1387  */
1389 AVFormatContext *avformat_alloc_output_context(const char *format,
1390  AVOutputFormat *oformat,
1391  const char *filename);
1392 #endif
1393 
1394 /**
1395  * Allocate an AVFormatContext for an output format.
1396  * avformat_free_context() can be used to free the context and
1397  * everything allocated by the framework within it.
1398  *
1399  * @param *ctx is set to the created format context, or to NULL in
1400  * case of failure
1401  * @param oformat format to use for allocating the context, if NULL
1402  * format_name and filename are used instead
1403  * @param format_name the name of output format to use for allocating the
1404  * context, if NULL filename is used instead
1405  * @param filename the name of the filename to use for allocating the
1406  * context, may be NULL
1407  * @return >= 0 in case of success, a negative AVERROR code in case of
1408  * failure
1409  */
1411  const char *format_name, const char *filename);
1412 
1413 /**
1414  * @addtogroup lavf_decoding
1415  * @{
1416  */
1417 
1418 /**
1419  * Find AVInputFormat based on the short name of the input format.
1420  */
1421 AVInputFormat *av_find_input_format(const char *short_name);
1422 
1423 /**
1424  * Guess the file format.
1425  *
1426  * @param is_opened Whether the file is already opened; determines whether
1427  * demuxers with or without AVFMT_NOFILE are probed.
1428  */
1429 AVInputFormat *av_probe_input_format(AVProbeData *pd, int is_opened);
1430 
1431 /**
1432  * Guess the file format.
1433  *
1434  * @param is_opened Whether the file is already opened; determines whether
1435  * demuxers with or without AVFMT_NOFILE are probed.
1436  * @param score_max A probe score larger that this is required to accept a
1437  * detection, the variable is set to the actual detection
1438  * score afterwards.
1439  * If the score is <= AVPROBE_SCORE_MAX / 4 it is recommended
1440  * to retry with a larger probe buffer.
1441  */
1442 AVInputFormat *av_probe_input_format2(AVProbeData *pd, int is_opened, int *score_max);
1443 
1444 /**
1445  * Guess the file format.
1446  *
1447  * @param is_opened Whether the file is already opened; determines whether
1448  * demuxers with or without AVFMT_NOFILE are probed.
1449  * @param score_ret The score of the best detection.
1450  */
1451 AVInputFormat *av_probe_input_format3(AVProbeData *pd, int is_opened, int *score_ret);
1452 
1453 /**
1454  * Probe a bytestream to determine the input format. Each time a probe returns
1455  * with a score that is too low, the probe buffer size is increased and another
1456  * attempt is made. When the maximum probe size is reached, the input format
1457  * with the highest score is returned.
1458  *
1459  * @param pb the bytestream to probe
1460  * @param fmt the input format is put here
1461  * @param filename the filename of the stream
1462  * @param logctx the log context
1463  * @param offset the offset within the bytestream to probe from
1464  * @param max_probe_size the maximum probe buffer size (zero for default)
1465  * @return 0 in case of success, a negative value corresponding to an
1466  * AVERROR code otherwise
1467  */
1469  const char *filename, void *logctx,
1470  unsigned int offset, unsigned int max_probe_size);
1471 
1472 /**
1473  * Open an input stream and read the header. The codecs are not opened.
1474  * The stream must be closed with av_close_input_file().
1475  *
1476  * @param ps Pointer to user-supplied AVFormatContext (allocated by avformat_alloc_context).
1477  * May be a pointer to NULL, in which case an AVFormatContext is allocated by this
1478  * function and written into ps.
1479  * Note that a user-supplied AVFormatContext will be freed on failure.
1480  * @param filename Name of the stream to open.
1481  * @param fmt If non-NULL, this parameter forces a specific input format.
1482  * Otherwise the format is autodetected.
1483  * @param options A dictionary filled with AVFormatContext and demuxer-private options.
1484  * On return this parameter will be destroyed and replaced with a dict containing
1485  * options that were not found. May be NULL.
1486  *
1487  * @return 0 on success, a negative AVERROR on failure.
1488  *
1489  * @note If you want to use custom IO, preallocate the format context and set its pb field.
1490  */
1491 int avformat_open_input(AVFormatContext **ps, const char *filename, AVInputFormat *fmt, AVDictionary **options);
1492 
1495 
1496 #if FF_API_FORMAT_PARAMETERS
1497 /**
1498  * Read packets of a media file to get stream information. This
1499  * is useful for file formats with no headers such as MPEG. This
1500  * function also computes the real framerate in case of MPEG-2 repeat
1501  * frame mode.
1502  * The logical file position is not changed by this function;
1503  * examined packets may be buffered for later processing.
1504  *
1505  * @param ic media file handle
1506  * @return >=0 if OK, AVERROR_xxx on error
1507  * @todo Let the user decide somehow what information is needed so that
1508  * we do not waste time getting stuff the user does not need.
1509  *
1510  * @deprecated use avformat_find_stream_info.
1511  */
1513 int av_find_stream_info(AVFormatContext *ic);
1514 #endif
1515 
1516 /**
1517  * Read packets of a media file to get stream information. This
1518  * is useful for file formats with no headers such as MPEG. This
1519  * function also computes the real framerate in case of MPEG-2 repeat
1520  * frame mode.
1521  * The logical file position is not changed by this function;
1522  * examined packets may be buffered for later processing.
1523  *
1524  * @param ic media file handle
1525  * @param options If non-NULL, an ic.nb_streams long array of pointers to
1526  * dictionaries, where i-th member contains options for
1527  * codec corresponding to i-th stream.
1528  * On return each dictionary will be filled with options that were not found.
1529  * @return >=0 if OK, AVERROR_xxx on error
1530  *
1531  * @note this function isn't guaranteed to open all the codecs, so
1532  * options being non-empty at return is a perfectly normal behavior.
1533  *
1534  * @todo Let the user decide somehow what information is needed so that
1535  * we do not waste time getting stuff the user does not need.
1536  */
1538 
1539 /**
1540  * Find the programs which belong to a given stream.
1541  *
1542  * @param ic media file handle
1543  * @param last the last found program, the search will start after this
1544  * program, or from the beginning if it is NULL
1545  * @param s stream index
1546  * @return the next program which belongs to s, NULL if no program is found or
1547  * the last program is not among the programs of ic.
1548  */
1550 
1551 /**
1552  * Find the "best" stream in the file.
1553  * The best stream is determined according to various heuristics as the most
1554  * likely to be what the user expects.
1555  * If the decoder parameter is non-NULL, av_find_best_stream will find the
1556  * default decoder for the stream's codec; streams for which no decoder can
1557  * be found are ignored.
1558  *
1559  * @param ic media file handle
1560  * @param type stream type: video, audio, subtitles, etc.
1561  * @param wanted_stream_nb user-requested stream number,
1562  * or -1 for automatic selection
1563  * @param related_stream try to find a stream related (eg. in the same
1564  * program) to this one, or -1 if none
1565  * @param decoder_ret if non-NULL, returns the decoder for the
1566  * selected stream
1567  * @param flags flags; none are currently defined
1568  * @return the non-negative stream number in case of success,
1569  * AVERROR_STREAM_NOT_FOUND if no stream with the requested type
1570  * could be found,
1571  * AVERROR_DECODER_NOT_FOUND if streams were found but no decoder
1572  * @note If av_find_best_stream returns successfully and decoder_ret is not
1573  * NULL, then *decoder_ret is guaranteed to be set to a valid AVCodec.
1574  */
1576  enum AVMediaType type,
1577  int wanted_stream_nb,
1578  int related_stream,
1579  AVCodec **decoder_ret,
1580  int flags);
1581 
1582 #if FF_API_READ_PACKET
1583 /**
1584  * @deprecated use AVFMT_FLAG_NOFILLIN | AVFMT_FLAG_NOPARSE to read raw
1585  * unprocessed packets
1586  *
1587  * Read a transport packet from a media file.
1588  *
1589  * This function is obsolete and should never be used.
1590  * Use av_read_frame() instead.
1591  *
1592  * @param s media file handle
1593  * @param pkt is filled
1594  * @return 0 if OK, AVERROR_xxx on error
1595  */
1597 int av_read_packet(AVFormatContext *s, AVPacket *pkt);
1598 #endif
1599 
1600 /**
1601  * Return the next frame of a stream.
1602  * This function returns what is stored in the file, and does not validate
1603  * that what is there are valid frames for the decoder. It will split what is
1604  * stored in the file into frames and return one for each call. It will not
1605  * omit invalid data between valid frames so as to give the decoder the maximum
1606  * information possible for decoding.
1607  *
1608  * If pkt->destruct is NULL, then the packet is valid until the next
1609  * av_read_frame() or until av_close_input_file(). Otherwise the packet is valid
1610  * indefinitely. In both cases the packet must be freed with
1611  * av_free_packet when it is no longer needed. For video, the packet contains
1612  * exactly one frame. For audio, it contains an integer number of frames if each
1613  * frame has a known fixed size (e.g. PCM or ADPCM data). If the audio frames
1614  * have a variable size (e.g. MPEG audio), then it contains one frame.
1615  *
1616  * pkt->pts, pkt->dts and pkt->duration are always set to correct
1617  * values in AVStream.time_base units (and guessed if the format cannot
1618  * provide them). pkt->pts can be AV_NOPTS_VALUE if the video format
1619  * has B-frames, so it is better to rely on pkt->dts if you do not
1620  * decompress the payload.
1621  *
1622  * @return 0 if OK, < 0 on error or end of file
1623  */
1625 
1626 /**
1627  * Seek to the keyframe at timestamp.
1628  * 'timestamp' in 'stream_index'.
1629  * @param stream_index If stream_index is (-1), a default
1630  * stream is selected, and timestamp is automatically converted
1631  * from AV_TIME_BASE units to the stream specific time_base.
1632  * @param timestamp Timestamp in AVStream.time_base units
1633  * or, if no stream is specified, in AV_TIME_BASE units.
1634  * @param flags flags which select direction and seeking mode
1635  * @return >= 0 on success
1636  */
1637 int av_seek_frame(AVFormatContext *s, int stream_index, int64_t timestamp,
1638  int flags);
1639 
1640 /**
1641  * Seek to timestamp ts.
1642  * Seeking will be done so that the point from which all active streams
1643  * can be presented successfully will be closest to ts and within min/max_ts.
1644  * Active streams are all streams that have AVStream.discard < AVDISCARD_ALL.
1645  *
1646  * If flags contain AVSEEK_FLAG_BYTE, then all timestamps are in bytes and
1647  * are the file position (this may not be supported by all demuxers).
1648  * If flags contain AVSEEK_FLAG_FRAME, then all timestamps are in frames
1649  * in the stream with stream_index (this may not be supported by all demuxers).
1650  * Otherwise all timestamps are in units of the stream selected by stream_index
1651  * or if stream_index is -1, in AV_TIME_BASE units.
1652  * If flags contain AVSEEK_FLAG_ANY, then non-keyframes are treated as
1653  * keyframes (this may not be supported by all demuxers).
1654  *
1655  * @param stream_index index of the stream which is used as time base reference
1656  * @param min_ts smallest acceptable timestamp
1657  * @param ts target timestamp
1658  * @param max_ts largest acceptable timestamp
1659  * @param flags flags
1660  * @return >=0 on success, error code otherwise
1661  *
1662  * @note This is part of the new seek API which is still under construction.
1663  * Thus do not use this yet. It may change at any time, do not expect
1664  * ABI compatibility yet!
1665  */
1666 int avformat_seek_file(AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags);
1667 
1668 /**
1669  * Start playing a network-based stream (e.g. RTSP stream) at the
1670  * current position.
1671  */
1673 
1674 /**
1675  * Pause a network-based stream (e.g. RTSP stream).
1676  *
1677  * Use av_read_play() to resume it.
1678  */
1680 
1681 #if FF_API_CLOSE_INPUT_FILE
1682 /**
1683  * @deprecated use avformat_close_input()
1684  * Close a media file (but not its codecs).
1685  *
1686  * @param s media file handle
1687  */
1689 void av_close_input_file(AVFormatContext *s);
1690 #endif
1691 
1692 /**
1693  * Close an opened input AVFormatContext. Free it and all its contents
1694  * and set *s to NULL.
1695  */
1697 /**
1698  * @}
1699  */
1700 
1701 #if FF_API_NEW_STREAM
1702 /**
1703  * Add a new stream to a media file.
1704  *
1705  * Can only be called in the read_header() function. If the flag
1706  * AVFMTCTX_NOHEADER is in the format context, then new streams
1707  * can be added in read_packet too.
1708  *
1709  * @param s media file handle
1710  * @param id file-format-dependent stream ID
1711  */
1713 AVStream *av_new_stream(AVFormatContext *s, int id);
1714 #endif
1715 
1716 #if FF_API_SET_PTS_INFO
1717 /**
1718  * @deprecated this function is not supposed to be called outside of lavf
1719  */
1721 void av_set_pts_info(AVStream *s, int pts_wrap_bits,
1722  unsigned int pts_num, unsigned int pts_den);
1723 #endif
1724 
1725 #define AVSEEK_FLAG_BACKWARD 1 ///< seek backward
1726 #define AVSEEK_FLAG_BYTE 2 ///< seeking based on position in bytes
1727 #define AVSEEK_FLAG_ANY 4 ///< seek to any frame, even non-keyframes
1728 #define AVSEEK_FLAG_FRAME 8 ///< seeking based on frame number
1729 
1730 /**
1731  * @addtogroup lavf_encoding
1732  * @{
1733  */
1734 /**
1735  * Allocate the stream private data and write the stream header to
1736  * an output media file.
1737  *
1738  * @param s Media file handle, must be allocated with avformat_alloc_context().
1739  * Its oformat field must be set to the desired output format;
1740  * Its pb field must be set to an already openened AVIOContext.
1741  * @param options An AVDictionary filled with AVFormatContext and muxer-private options.
1742  * On return this parameter will be destroyed and replaced with a dict containing
1743  * options that were not found. May be NULL.
1744  *
1745  * @return 0 on success, negative AVERROR on failure.
1746  *
1747  * @see av_opt_find, av_dict_set, avio_open, av_oformat_next.
1748  */
1750 
1751 /**
1752  * Write a packet to an output media file.
1753  *
1754  * The packet shall contain one audio or video frame.
1755  * The packet must be correctly interleaved according to the container
1756  * specification, if not then av_interleaved_write_frame must be used.
1757  *
1758  * @param s media file handle
1759  * @param pkt The packet, which contains the stream_index, buf/buf_size,
1760  * dts/pts, ...
1761  * This can be NULL (at any time, not just at the end), in
1762  * order to immediately flush data buffered within the muxer,
1763  * for muxers that buffer up data internally before writing it
1764  * to the output.
1765  * @return < 0 on error, = 0 if OK, 1 if flushed and there is no more data to flush
1766  */
1768 
1769 /**
1770  * Write a packet to an output media file ensuring correct interleaving.
1771  *
1772  * The packet must contain one audio or video frame.
1773  * If the packets are already correctly interleaved, the application should
1774  * call av_write_frame() instead as it is slightly faster. It is also important
1775  * to keep in mind that completely non-interleaved input will need huge amounts
1776  * of memory to interleave with this, so it is preferable to interleave at the
1777  * demuxer level.
1778  *
1779  * @param s media file handle
1780  * @param pkt The packet containing the data to be written. Libavformat takes
1781  * ownership of the data and will free it when it sees fit using the packet's
1782  * @ref AVPacket.destruct "destruct" field. The caller must not access the data
1783  * after this function returns, as it may already be freed.
1784  * This can be NULL (at any time, not just at the end), to flush the
1785  * interleaving queues.
1786  * Packet's @ref AVPacket.stream_index "stream_index" field must be set to the
1787  * index of the corresponding stream in @ref AVFormatContext.streams
1788  * "s.streams".
1789  * It is very strongly recommended that timing information (@ref AVPacket.pts
1790  * "pts", @ref AVPacket.dts "dts" @ref AVPacket.duration "duration") is set to
1791  * correct values.
1792  *
1793  * @return 0 on success, a negative AVERROR on error.
1794  */
1796 
1797 #if FF_API_INTERLEAVE_PACKET
1798 /**
1799  * @deprecated this function was never meant to be called by the user
1800  * programs.
1801  */
1803 int av_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out,
1804  AVPacket *pkt, int flush);
1805 #endif
1806 
1807 /**
1808  * Write the stream trailer to an output media file and free the
1809  * file private data.
1810  *
1811  * May only be called after a successful call to avformat_write_header.
1812  *
1813  * @param s media file handle
1814  * @return 0 if OK, AVERROR_xxx on error
1815  */
1817 
1818 /**
1819  * Return the output format in the list of registered output formats
1820  * which best matches the provided parameters, or return NULL if
1821  * there is no match.
1822  *
1823  * @param short_name if non-NULL checks if short_name matches with the
1824  * names of the registered formats
1825  * @param filename if non-NULL checks if filename terminates with the
1826  * extensions of the registered formats
1827  * @param mime_type if non-NULL checks if mime_type matches with the
1828  * MIME type of the registered formats
1829  */
1830 AVOutputFormat *av_guess_format(const char *short_name,
1831  const char *filename,
1832  const char *mime_type);
1833 
1834 /**
1835  * Guess the codec ID based upon muxer and filename.
1836  */
1837 enum AVCodecID av_guess_codec(AVOutputFormat *fmt, const char *short_name,
1838  const char *filename, const char *mime_type,
1839  enum AVMediaType type);
1840 
1841 /**
1842  * Get timing information for the data currently output.
1843  * The exact meaning of "currently output" depends on the format.
1844  * It is mostly relevant for devices that have an internal buffer and/or
1845  * work in real time.
1846  * @param s media file handle
1847  * @param stream stream in the media file
1848  * @param[out] dts DTS of the last packet output for the stream, in stream
1849  * time_base units
1850  * @param[out] wall absolute time when that packet whas output,
1851  * in microsecond
1852  * @return 0 if OK, AVERROR(ENOSYS) if the format does not support it
1853  * Note: some formats or devices may not allow to measure dts and wall
1854  * atomically.
1855  */
1856 int av_get_output_timestamp(struct AVFormatContext *s, int stream,
1857  int64_t *dts, int64_t *wall);
1858 
1859 
1860 /**
1861  * @}
1862  */
1863 
1864 
1865 /**
1866  * @defgroup lavf_misc Utility functions
1867  * @ingroup libavf
1868  * @{
1869  *
1870  * Miscellaneous utility functions related to both muxing and demuxing
1871  * (or neither).
1872  */
1873 
1874 /**
1875  * Send a nice hexadecimal dump of a buffer to the specified file stream.
1876  *
1877  * @param f The file stream pointer where the dump should be sent to.
1878  * @param buf buffer
1879  * @param size buffer size
1880  *
1881  * @see av_hex_dump_log, av_pkt_dump2, av_pkt_dump_log2
1882  */
1883 void av_hex_dump(FILE *f, const uint8_t *buf, int size);
1884 
1885 /**
1886  * Send a nice hexadecimal dump of a buffer to the log.
1887  *
1888  * @param avcl A pointer to an arbitrary struct of which the first field is a
1889  * pointer to an AVClass struct.
1890  * @param level The importance level of the message, lower values signifying
1891  * higher importance.
1892  * @param buf buffer
1893  * @param size buffer size
1894  *
1895  * @see av_hex_dump, av_pkt_dump2, av_pkt_dump_log2
1896  */
1897 void av_hex_dump_log(void *avcl, int level, const uint8_t *buf, int size);
1898 
1899 /**
1900  * Send a nice dump of a packet to the specified file stream.
1901  *
1902  * @param f The file stream pointer where the dump should be sent to.
1903  * @param pkt packet to dump
1904  * @param dump_payload True if the payload must be displayed, too.
1905  * @param st AVStream that the packet belongs to
1906  */
1907 void av_pkt_dump2(FILE *f, AVPacket *pkt, int dump_payload, AVStream *st);
1908 
1909 
1910 /**
1911  * Send a nice dump of a packet to the log.
1912  *
1913  * @param avcl A pointer to an arbitrary struct of which the first field is a
1914  * pointer to an AVClass struct.
1915  * @param level The importance level of the message, lower values signifying
1916  * higher importance.
1917  * @param pkt packet to dump
1918  * @param dump_payload True if the payload must be displayed, too.
1919  * @param st AVStream that the packet belongs to
1920  */
1921 void av_pkt_dump_log2(void *avcl, int level, AVPacket *pkt, int dump_payload,
1922  AVStream *st);
1923 
1924 /**
1925  * Get the AVCodecID for the given codec tag tag.
1926  * If no codec id is found returns AV_CODEC_ID_NONE.
1927  *
1928  * @param tags list of supported codec_id-codec_tag pairs, as stored
1929  * in AVInputFormat.codec_tag and AVOutputFormat.codec_tag
1930  */
1931 enum AVCodecID av_codec_get_id(const struct AVCodecTag * const *tags, unsigned int tag);
1932 
1933 /**
1934  * Get the codec tag for the given codec id id.
1935  * If no codec tag is found returns 0.
1936  *
1937  * @param tags list of supported codec_id-codec_tag pairs, as stored
1938  * in AVInputFormat.codec_tag and AVOutputFormat.codec_tag
1939  */
1940 unsigned int av_codec_get_tag(const struct AVCodecTag * const *tags, enum AVCodecID id);
1941 
1942 /**
1943  * Get the codec tag for the given codec id.
1944  *
1945  * @param tags list of supported codec_id - codec_tag pairs, as stored
1946  * in AVInputFormat.codec_tag and AVOutputFormat.codec_tag
1947  * @param id codec id that should be searched for in the list
1948  * @param tag A pointer to the found tag
1949  * @return 0 if id was not found in tags, > 0 if it was found
1950  */
1951 int av_codec_get_tag2(const struct AVCodecTag * const *tags, enum AVCodecID id,
1952  unsigned int *tag);
1953 
1955 
1956 /**
1957  * Get the index for a specific timestamp.
1958  * @param flags if AVSEEK_FLAG_BACKWARD then the returned index will correspond
1959  * to the timestamp which is <= the requested one, if backward
1960  * is 0, then it will be >=
1961  * if AVSEEK_FLAG_ANY seek to any frame, only keyframes otherwise
1962  * @return < 0 if no such timestamp could be found
1963  */
1964 int av_index_search_timestamp(AVStream *st, int64_t timestamp, int flags);
1965 
1966 /**
1967  * Add an index entry into a sorted list. Update the entry if the list
1968  * already contains it.
1969  *
1970  * @param timestamp timestamp in the time base of the given stream
1971  */
1972 int av_add_index_entry(AVStream *st, int64_t pos, int64_t timestamp,
1973  int size, int distance, int flags);
1974 
1975 
1976 /**
1977  * Split a URL string into components.
1978  *
1979  * The pointers to buffers for storing individual components may be null,
1980  * in order to ignore that component. Buffers for components not found are
1981  * set to empty strings. If the port is not found, it is set to a negative
1982  * value.
1983  *
1984  * @param proto the buffer for the protocol
1985  * @param proto_size the size of the proto buffer
1986  * @param authorization the buffer for the authorization
1987  * @param authorization_size the size of the authorization buffer
1988  * @param hostname the buffer for the host name
1989  * @param hostname_size the size of the hostname buffer
1990  * @param port_ptr a pointer to store the port number in
1991  * @param path the buffer for the path
1992  * @param path_size the size of the path buffer
1993  * @param url the URL to split
1994  */
1995 void av_url_split(char *proto, int proto_size,
1996  char *authorization, int authorization_size,
1997  char *hostname, int hostname_size,
1998  int *port_ptr,
1999  char *path, int path_size,
2000  const char *url);
2001 
2002 
2004  int index,
2005  const char *url,
2006  int is_output);
2007 
2008 /**
2009  * Return in 'buf' the path with '%d' replaced by a number.
2010  *
2011  * Also handles the '%0nd' format where 'n' is the total number
2012  * of digits and '%%'.
2013  *
2014  * @param buf destination buffer
2015  * @param buf_size destination buffer size
2016  * @param path numbered sequence string
2017  * @param number frame number
2018  * @return 0 if OK, -1 on format error
2019  */
2020 int av_get_frame_filename(char *buf, int buf_size,
2021  const char *path, int number);
2022 
2023 /**
2024  * Check whether filename actually is a numbered sequence generator.
2025  *
2026  * @param filename possible numbered sequence string
2027  * @return 1 if a valid numbered sequence string, 0 otherwise
2028  */
2029 int av_filename_number_test(const char *filename);
2030 
2031 /**
2032  * Generate an SDP for an RTP session.
2033  *
2034  * Note, this overwrites the id values of AVStreams in the muxer contexts
2035  * for getting unique dynamic payload types.
2036  *
2037  * @param ac array of AVFormatContexts describing the RTP streams. If the
2038  * array is composed by only one context, such context can contain
2039  * multiple AVStreams (one AVStream per RTP stream). Otherwise,
2040  * all the contexts in the array (an AVCodecContext per RTP stream)
2041  * must contain only one AVStream.
2042  * @param n_files number of AVCodecContexts contained in ac
2043  * @param buf buffer where the SDP will be stored (must be allocated by
2044  * the caller)
2045  * @param size the size of the buffer
2046  * @return 0 if OK, AVERROR_xxx on error
2047  */
2048 int av_sdp_create(AVFormatContext *ac[], int n_files, char *buf, int size);
2049 
2050 /**
2051  * Return a positive value if the given filename has one of the given
2052  * extensions, 0 otherwise.
2053  *
2054  * @param extensions a comma-separated list of filename extensions
2055  */
2056 int av_match_ext(const char *filename, const char *extensions);
2057 
2058 /**
2059  * Test if the given container can store a codec.
2060  *
2061  * @param std_compliance standards compliance level, one of FF_COMPLIANCE_*
2062  *
2063  * @return 1 if codec with ID codec_id can be stored in ofmt, 0 if it cannot.
2064  * A negative number if this information is not available.
2065  */
2066 int avformat_query_codec(AVOutputFormat *ofmt, enum AVCodecID codec_id, int std_compliance);
2067 
2068 /**
2069  * @defgroup riff_fourcc RIFF FourCCs
2070  * @{
2071  * Get the tables mapping RIFF FourCCs to libavcodec AVCodecIDs. The tables are
2072  * meant to be passed to av_codec_get_id()/av_codec_get_tag() as in the
2073  * following code:
2074  * @code
2075  * uint32_t tag = MKTAG('H', '2', '6', '4');
2076  * const struct AVCodecTag *table[] = { avformat_get_riff_video_tags(), 0 };
2077  * enum AVCodecID id = av_codec_get_id(table, tag);
2078  * @endcode
2079  */
2080 /**
2081  * @return the table mapping RIFF FourCCs for video to libavcodec AVCodecID.
2082  */
2083 const struct AVCodecTag *avformat_get_riff_video_tags(void);
2084 /**
2085  * @return the table mapping RIFF FourCCs for audio to AVCodecID.
2086  */
2087 const struct AVCodecTag *avformat_get_riff_audio_tags(void);
2088 
2089 /**
2090  * @}
2091  */
2092 
2093 /**
2094  * Guess the sample aspect ratio of a frame, based on both the stream and the
2095  * frame aspect ratio.
2096  *
2097  * Since the frame aspect ratio is set by the codec but the stream aspect ratio
2098  * is set by the demuxer, these two may not be equal. This function tries to
2099  * return the value that you should use if you would like to display the frame.
2100  *
2101  * Basic logic is to use the stream aspect ratio if it is set to something sane
2102  * otherwise use the frame aspect ratio. This way a container setting, which is
2103  * usually easy to modify can override the coded value in the frames.
2104  *
2105  * @param format the format context which the stream is part of
2106  * @param stream the stream which the frame is part of
2107  * @param frame the frame with the aspect ratio to be determined
2108  * @return the guessed (valid) sample_aspect_ratio, 0/1 if no idea
2109  */
2111 
2112 /**
2113  * Check if the stream st contained in s is matched by the stream specifier
2114  * spec.
2115  *
2116  * See the "stream specifiers" chapter in the documentation for the syntax
2117  * of spec.
2118  *
2119  * @return >0 if st is matched by spec;
2120  * 0 if st is not matched by spec;
2121  * AVERROR code if spec is invalid
2122  *
2123  * @note A stream specifier can match several streams in the format.
2124  */
2126  const char *spec);
2127 
2129 
2130 
2131 /**
2132  * @}
2133  */
2134 
2135 #endif /* AVFORMAT_AVFORMAT_H */