FFmpeg/libavformat/avformat.h

/*
 * copyright (c) 2001 Fabrice Bellard
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#ifndef AVFORMAT_AVFORMAT_H
#define AVFORMAT_AVFORMAT_H

/**
 * @file
 * @ingroup libavf
 * Main libavformat public API header
 */

/**
 * @defgroup libavf I/O and Muxing/Demuxing Library
 * @{
 *
 * Libavformat (lavf) is a library for dealing with various media container
 * formats. Its main two purposes are demuxing - i.e. splitting a media file
 * into component streams, and the reverse process of muxing - writing supplied
 * data in a specified container format. It also has an @ref lavf_io
 * "I/O module" which supports a number of protocols for accessing the data (e.g.
 * file, tcp, http and others). Before using lavf, you need to call
 * av_register_all() to register all compiled muxers, demuxers and protocols.
 * Unless you are absolutely sure you won't use libavformat's network
 * capabilities, you should also call avformat_network_init().
 *
 * A supported input format is described by an AVInputFormat struct, conversely
 * an output format is described by AVOutputFormat. You can iterate over all
 * registered input/output formats using the av_iformat_next() /
 * av_oformat_next() functions. The protocols layer is not part of the public
 * API, so you can only get the names of supported protocols with the
 * avio_enum_protocols() function.
 *
 * Main lavf structure used for both muxing and demuxing is AVFormatContext,
 * which exports all information about the file being read or written. As with
 * most Libavformat structures, its size is not part of public ABI, so it cannot be
 * allocated on stack or directly with av_malloc(). To create an
 * AVFormatContext, use avformat_alloc_context() (some functions, like
 * avformat_open_input() might do that for you).
 *
 * Most importantly an AVFormatContext contains:
 * @li the @ref AVFormatContext.iformat "input" or @ref AVFormatContext.oformat
 * "output" format. It is either autodetected or set by user for input;
 * always set by user for output.
 * @li an @ref AVFormatContext.streams "array" of AVStreams, which describe all
 * elementary streams stored in the file. AVStreams are typically referred to
 * using their index in this array.
 * @li an @ref AVFormatContext.pb "I/O context". It is either opened by lavf or
 * set by user for input, always set by user for output (unless you are dealing
 * with an AVFMT_NOFILE format).
 *
 * @section lavf_options Passing options to (de)muxers
 * Lavf allows to configure muxers and demuxers using the @ref avoptions
 * mechanism. Generic (format-independent) libavformat options are provided by
 * AVFormatContext, they can be examined from a user program by calling
 * av_opt_next() / av_opt_find() on an allocated AVFormatContext (or its AVClass
 * from avformat_get_class()). Private (format-specific) options are provided by
 * AVFormatContext.priv_data if and only if AVInputFormat.priv_class /
 * AVOutputFormat.priv_class of the corresponding format struct is non-NULL.
 * Further options may be provided by the @ref AVFormatContext.pb "I/O context",
 * if its AVClass is non-NULL, and the protocols layer. See the discussion on
 * nesting in @ref avoptions documentation to learn how to access those.
 *
 * @defgroup lavf_decoding Demuxing
 * @{
 * Demuxers read a media file and split it into chunks of data (@em packets). A
 * @ref AVPacket "packet" contains one or more encoded frames which belongs to a
 * single elementary stream. In the lavf API this process is represented by the
 * avformat_open_input() function for opening a file, av_read_frame() for
 * reading a single packet and finally avformat_close_input(), which does the
 * cleanup.
 *
 * @section lavf_decoding_open Opening a media file
 * The minimum information required to open a file is its URL or filename, which
 * is passed to avformat_open_input(), as in the following code:
 * @code
 * const char    *url = "in.mp3";
 * AVFormatContext *s = NULL;
 * int ret = avformat_open_input(&s, url, NULL, NULL);
 * if (ret < 0)
 *     abort();
 * @endcode
 * The above code attempts to allocate an AVFormatContext, open the
 * specified file (autodetecting the format) and read the header, exporting the
 * information stored there into s. Some formats do not have a header or do not
 * store enough information there, so it is recommended that you call the
 * avformat_find_stream_info() function which tries to read and decode a few
 * frames to find missing information.
 *
 * In some cases you might want to preallocate an AVFormatContext yourself with
 * avformat_alloc_context() and do some tweaking on it before passing it to
 * avformat_open_input(). One such case is when you want to use custom functions
 * for reading input data instead of lavf internal I/O layer.
 * To do that, create your own AVIOContext with avio_alloc_context(), passing
 * your reading callbacks to it. Then set the @em pb field of your
 * AVFormatContext to newly created AVIOContext.
 *
 * Since the format of the opened file is in general not known until after
 * avformat_open_input() has returned, it is not possible to set demuxer private
 * options on a preallocated context. Instead, the options should be passed to
 * avformat_open_input() wrapped in an AVDictionary:
 * @code
 * AVDictionary *options = NULL;
 * av_dict_set(&options, "video_size", "640x480", 0);
 * av_dict_set(&options, "pixel_format", "rgb24", 0);
 *
 * if (avformat_open_input(&s, url, NULL, &options) < 0)
 *     abort();
 * av_dict_free(&options);
 * @endcode
 * This code passes the private options 'video_size' and 'pixel_format' to the
 * demuxer. They would be necessary for e.g. the rawvideo demuxer, since it
 * cannot know how to interpret raw video data otherwise. If the format turns
 * out to be something different than raw video, those options will not be
 * recognized by the demuxer and therefore will not be applied. Such unrecognized
 * options are then returned in the options dictionary (recognized options are
 * consumed). The calling program can handle such unrecognized options as it
 * wishes, e.g.
 * @code
 * AVDictionaryEntry *e;
 * if (e = av_dict_get(options, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
 *     fprintf(stderr, "Option %s not recognized by the demuxer.\n", e->key);
 *     abort();
 * }
 * @endcode
 *
 * After you have finished reading the file, you must close it with
 * avformat_close_input(). It will free everything associated with the file.
 *
 * @section lavf_decoding_read Reading from an opened file
 * Reading data from an opened AVFormatContext is done by repeatedly calling
 * av_read_frame() on it. Each call, if successful, will return an AVPacket
 * containing encoded data for one AVStream, identified by
 * AVPacket.stream_index. This packet may be passed straight into the libavcodec
 * decoding functions avcodec_decode_video2(), avcodec_decode_audio4() or
 * avcodec_decode_subtitle2() if the caller wishes to decode the data.
 *
 * AVPacket.pts, AVPacket.dts and AVPacket.duration timing information will be
 * set if known. They may also be unset (i.e. AV_NOPTS_VALUE for
 * pts/dts, 0 for duration) if the stream does not provide them. The timing
 * information will be in AVStream.time_base units, i.e. it has to be
 * multiplied by the timebase to convert them to seconds.
 *
 * If AVPacket.buf is set on the returned packet, then the packet is
 * allocated dynamically and the user may keep it indefinitely.
 * Otherwise, if AVPacket.buf is NULL, the packet data is backed by a
 * static storage somewhere inside the demuxer and the packet is only valid
 * until the next av_read_frame() call or closing the file. If the caller
 * requires a longer lifetime, av_dup_packet() will make an av_malloc()ed copy
 * of it.
 * In both cases, the packet must be freed with av_free_packet() when it is no
 * longer needed.
 *
 * @section lavf_decoding_seek Seeking
 * @}
 *
 * @defgroup lavf_encoding Muxing
 * @{
 * Muxers take encoded data in the form of @ref AVPacket "AVPackets" and write
 * it into files or other output bytestreams in the specified container format.
 *
 * The main API functions for muxing are avformat_write_header() for writing the
 * file header, av_write_frame() / av_interleaved_write_frame() for writing the
 * packets and av_write_trailer() for finalizing the file.
 *
 * At the beginning of the muxing process, the caller must first call
 * avformat_alloc_context() to create a muxing context. The caller then sets up
 * the muxer by filling the various fields in this context:
 *
 * - The @ref AVFormatContext.oformat "oformat" field must be set to select the
 *   muxer that will be used.
 * - Unless the format is of the AVFMT_NOFILE type, the @ref AVFormatContext.pb
 *   "pb" field must be set to an opened IO context, either returned from
 *   avio_open2() or a custom one.
 * - Unless the format is of the AVFMT_NOSTREAMS type, at least one stream must
 *   be created with the avformat_new_stream() function. The caller should fill
 *   the @ref AVStream.codec "stream codec context" information, such as the
 *   codec @ref AVCodecContext.codec_type "type", @ref AVCodecContext.codec_id
 *   "id" and other parameters (e.g. width / height, the pixel or sample format,
 *   etc.) as known. The @ref AVCodecContext.time_base "codec timebase" should
 *   be set to the timebase that the caller desires to use for this stream (note
 *   that the timebase actually used by the muxer can be different, as will be
 *   described later).
 * - The caller may fill in additional information, such as @ref
 *   AVFormatContext.metadata "global" or @ref AVStream.metadata "per-stream"
 *   metadata, @ref AVFormatContext.chapters "chapters", @ref
 *   AVFormatContext.programs "programs", etc. as described in the
 *   AVFormatContext documentation. Whether such information will actually be
 *   stored in the output depends on what the container format and the muxer
 *   support.
 *
 * When the muxing context is fully set up, the caller must call
 * avformat_write_header() to initialize the muxer internals and write the file
 * header. Whether anything actually is written to the IO context at this step
 * depends on the muxer, but this function must always be called. Any muxer
 * private options must be passed in the options parameter to this function.
 *
 * The data is then sent to the muxer by repeatedly calling av_write_frame() or
 * av_interleaved_write_frame() (consult those functions' documentation for
 * discussion on the difference between them; only one of them may be used with
 * a single muxing context, they should not be mixed). Do note that the timing
 * information on the packets sent to the muxer must be in the corresponding
 * AVStream's timebase. That timebase is set by the muxer (in the
 * avformat_write_header() step) and may be different from the timebase the
 * caller set on the codec context.
 *
 * Once all the data has been written, the caller must call av_write_trailer()
 * to flush any buffered packets and finalize the output file, then close the IO
 * context (if any) and finally free the muxing context with
 * avformat_free_context().
 * @}
 *
 * @defgroup lavf_io I/O Read/Write
 * @{
 * @}
 *
 * @defgroup lavf_codec Demuxers
 * @{
 * @defgroup lavf_codec_native Native Demuxers
 * @{
 * @}
 * @defgroup lavf_codec_wrappers External library wrappers
 * @{
 * @}
 * @}
 * @defgroup lavf_protos I/O Protocols
 * @{
 * @}
 * @defgroup lavf_internal Internal
 * @{
 * @}
 * @}
 *
 */

#include <time.h>
#include <stdio.h>  /* FILE */
#include "libavcodec/avcodec.h"
#include "libavutil/dict.h"
#include "libavutil/log.h"

#include "avio.h"
#include "libavformat/version.h"

struct AVFormatContext;


/**
 * @defgroup metadata_api Public Metadata API
 * @{
 * @ingroup libavf
 * The metadata API allows libavformat to export metadata tags to a client
 * application when demuxing. Conversely it allows a client application to
 * set metadata when muxing.
 *
 * Metadata is exported or set as pairs of key/value strings in the 'metadata'
 * fields of the AVFormatContext, AVStream, AVChapter and AVProgram structs
 * using the @ref lavu_dict "AVDictionary" API. Like all strings in FFmpeg,
 * metadata is assumed to be UTF-8 encoded Unicode. Note that metadata
 * exported by demuxers isn't checked to be valid UTF-8 in most cases.
 *
 * Important concepts to keep in mind:
 * -  Keys are unique; there can never be 2 tags with the same key. This is
 *    also meant semantically, i.e., a demuxer should not knowingly produce
 *    several keys that are literally different but semantically identical.
 *    E.g., key=Author5, key=Author6. In this example, all authors must be
 *    placed in the same tag.
 * -  Metadata is flat, not hierarchical; there are no subtags. If you
 *    want to store, e.g., the email address of the child of producer Alice
 *    and actor Bob, that could have key=alice_and_bobs_childs_email_address.
 * -  Several modifiers can be applied to the tag name. This is done by
 *    appending a dash character ('-') and the modifier name in the order
 *    they appear in the list below -- e.g. foo-eng-sort, not foo-sort-eng.
 *    -  language -- a tag whose value is localized for a particular language
 *       is appended with the ISO 639-2/B 3-letter language code.
 *       For example: Author-ger=Michael, Author-eng=Mike
 *       The original/default language is in the unqualified "Author" tag.
 *       A demuxer should set a default if it sets any translated tag.
 *    -  sorting  -- a modified version of a tag that should be used for
 *       sorting will have '-sort' appended. E.g. artist="The Beatles",
 *       artist-sort="Beatles, The".
 *
 * -  Demuxers attempt to export metadata in a generic format, however tags
 *    with no generic equivalents are left as they are stored in the container.
 *    Follows a list of generic tag names:
 *
 @verbatim
 album        -- name of the set this work belongs to
 album_artist -- main creator of the set/album, if different from artist.
                 e.g. "Various Artists" for compilation albums.
 artist       -- main creator of the work
 comment      -- any additional description of the file.
 composer     -- who composed the work, if different from artist.
 copyright    -- name of copyright holder.
 creation_time-- date when the file was created, preferably in ISO 8601.
 date         -- date when the work was created, preferably in ISO 8601.
 disc         -- number of a subset, e.g. disc in a multi-disc collection.
 encoder      -- name/settings of the software/hardware that produced the file.
 encoded_by   -- person/group who created the file.
 filename     -- original name of the file.
 genre        -- <self-evident>.
 language     -- main language in which the work is performed, preferably
                 in ISO 639-2 format. Multiple languages can be specified by
                 separating them with commas.
 performer    -- artist who performed the work, if different from artist.
                 E.g for "Also sprach Zarathustra", artist would be "Richard
                 Strauss" and performer "London Philharmonic Orchestra".
 publisher    -- name of the label/publisher.
 service_name     -- name of the service in broadcasting (channel name).
 service_provider -- name of the service provider in broadcasting.
 title        -- name of the work.
 track        -- number of this work in the set, can be in form current/total.
 variant_bitrate -- the total bitrate of the bitrate variant that the current stream is part of
 @endverbatim
 *
 * Look in the examples section for an application example how to use the Metadata API.
 *
 * @}
 */

/* packet functions */


/**
 * Allocate and read the payload of a packet and initialize its
 * fields with default values.
 *
 * @param pkt packet
 * @param size desired payload size
 * @return >0 (read size) if OK, AVERROR_xxx otherwise
 */
int av_get_packet(AVIOContext *s, AVPacket *pkt, int size);


/**
 * Read data and append it to the current content of the AVPacket.
 * If pkt->size is 0 this is identical to av_get_packet.
 * Note that this uses av_grow_packet and thus involves a realloc
 * which is inefficient. Thus this function should only be used
 * when there is no reasonable way to know (an upper bound of)
 * the final size.
 *
 * @param pkt packet
 * @param size amount of data to read
 * @return >0 (read size) if OK, AVERROR_xxx otherwise, previous data
 *         will not be lost even if an error occurs.
 */
int av_append_packet(AVIOContext *s, AVPacket *pkt, int size);

/*************************************************/
/* fractional numbers for exact pts handling */

/**
 * The exact value of the fractional number is: 'val + num / den'.
 * num is assumed to be 0 <= num < den.
 */
typedef struct AVFrac {
    int64_t val, num, den;
} AVFrac;

/*************************************************/
/* input/output formats */

struct AVCodecTag;

/**
 * This structure contains the data a format has to probe a file.
 */
typedef struct AVProbeData {
    const char *filename;
    unsigned char *buf; /**< Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero. */
    int buf_size;       /**< Size of buf except extra allocated bytes */
} AVProbeData;

#define AVPROBE_SCORE_RETRY (AVPROBE_SCORE_MAX/4)
#define AVPROBE_SCORE_STREAM_RETRY (AVPROBE_SCORE_MAX/4-1)

#define AVPROBE_SCORE_EXTENSION  50 ///< score for file extension
#define AVPROBE_SCORE_MAX       100 ///< maximum score

#define AVPROBE_PADDING_SIZE 32             ///< extra allocated bytes at the end of the probe buffer

/// Demuxer will use avio_open, no opened file should be provided by the caller.
#define AVFMT_NOFILE        0x0001
#define AVFMT_NEEDNUMBER    0x0002 /**< Needs '%d' in filename. */
#define AVFMT_SHOW_IDS      0x0008 /**< Show format stream IDs numbers. */
#define AVFMT_RAWPICTURE    0x0020 /**< Format wants AVPicture structure for
                                      raw picture data. */
#define AVFMT_GLOBALHEADER  0x0040 /**< Format wants global header. */
#define AVFMT_NOTIMESTAMPS  0x0080 /**< Format does not need / have any timestamps. */
#define AVFMT_GENERIC_INDEX 0x0100 /**< Use generic index building code. */
#define AVFMT_TS_DISCONT    0x0200 /**< Format allows timestamp discontinuities. Note, muxers always require valid (monotone) timestamps */
#define AVFMT_VARIABLE_FPS  0x0400 /**< Format allows variable fps. */
#define AVFMT_NODIMENSIONS  0x0800 /**< Format does not need width/height */
#define AVFMT_NOSTREAMS     0x1000 /**< Format does not require any streams */
#define AVFMT_NOBINSEARCH   0x2000 /**< Format does not allow to fall back on binary search via read_timestamp */
#define AVFMT_NOGENSEARCH   0x4000 /**< Format does not allow to fall back on generic search */
#define AVFMT_NO_BYTE_SEEK  0x8000 /**< Format does not allow seeking by bytes */
#define AVFMT_ALLOW_FLUSH  0x10000 /**< Format allows flushing. If not set, the muxer will not receive a NULL packet in the write_packet function. */
#if LIBAVFORMAT_VERSION_MAJOR <= 54
#define AVFMT_TS_NONSTRICT 0x8020000 //we try to be compatible to the ABIs of ffmpeg and major forks
#else
#define AVFMT_TS_NONSTRICT 0x20000
#endif
                                   /**< Format does not require strictly
                                        increasing timestamps, but they must
                                        still be monotonic */
#define AVFMT_TS_NEGATIVE  0x40000 /**< Format allows muxing negative
                                        timestamps. If not set the timestamp
                                        will be shifted in av_write_frame and
                                        av_interleaved_write_frame so they
                                        start from 0.
                                        The user or muxer can override this through
                                        AVFormatContext.avoid_negative_ts
                                        */

#define AVFMT_SEEK_TO_PTS   0x4000000 /**< Seeking is based on PTS */

/**
 * @addtogroup lavf_encoding
 * @{
 */
typedef struct AVOutputFormat {
    const char *name;
    /**
     * Descriptive name for the format, meant to be more human-readable
     * than name. You should use the NULL_IF_CONFIG_SMALL() macro
     * to define it.
     */
    const char *long_name;
    const char *mime_type;
    const char *extensions; /**< comma-separated filename extensions */
    /* output support */
    enum AVCodecID audio_codec;    /**< default audio codec */
    enum AVCodecID video_codec;    /**< default video codec */
    enum AVCodecID subtitle_codec; /**< default subtitle codec */
    /**
     * can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER, AVFMT_RAWPICTURE,
     * AVFMT_GLOBALHEADER, AVFMT_NOTIMESTAMPS, AVFMT_VARIABLE_FPS,
     * AVFMT_NODIMENSIONS, AVFMT_NOSTREAMS, AVFMT_ALLOW_FLUSH,
     * AVFMT_TS_NONSTRICT
     */
    int flags;

    /**
     * List of supported codec_id-codec_tag pairs, ordered by "better
     * choice first". The arrays are all terminated by AV_CODEC_ID_NONE.
     */
    const struct AVCodecTag * const *codec_tag;


    const AVClass *priv_class; ///< AVClass for the private context

    /*****************************************************************
     * No fields below this line are part of the public API. They
     * may not be used outside of libavformat and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */
    struct AVOutputFormat *next;
    /**
     * size of private data so that it can be allocated in the wrapper
     */
    int priv_data_size;

    int (*write_header)(struct AVFormatContext *);
    /**
     * Write a packet. If AVFMT_ALLOW_FLUSH is set in flags,
     * pkt can be NULL in order to flush data buffered in the muxer.
     * When flushing, return 0 if there still is more data to flush,
     * or 1 if everything was flushed and there is no more buffered
     * data.
     */
    int (*write_packet)(struct AVFormatContext *, AVPacket *pkt);
    int (*write_trailer)(struct AVFormatContext *);
    /**
     * Currently only used to set pixel format if not YUV420P.
     */
    int (*interleave_packet)(struct AVFormatContext *, AVPacket *out,
                             AVPacket *in, int flush);
    /**
     * Test if the given codec can be stored in this container.
     *
     * @return 1 if the codec is supported, 0 if it is not.
     *         A negative number if unknown.
     *         MKTAG('A', 'P', 'I', 'C') if the codec is only supported as AV_DISPOSITION_ATTACHED_PIC
     */
    int (*query_codec)(enum AVCodecID id, int std_compliance);

    void (*get_output_timestamp)(struct AVFormatContext *s, int stream,
                                 int64_t *dts, int64_t *wall);
    /**
     * Allows sending messages from application to device.
     */
    int (*control_message)(struct AVFormatContext *s, int type,
                           void *data, size_t data_size);

    /**
     * Write an uncoded AVFrame.
     *
     * See av_write_uncoded_frame() for details.
     *
     * The library will free *frame afterwards, but the muxer can prevent it
     * by setting the pointer to NULL.
     */
    int (*write_uncoded_frame)(struct AVFormatContext *, int stream_index,
                               AVFrame **frame, unsigned flags);
} AVOutputFormat;
/**
 * @}
 */

/**
 * @addtogroup lavf_decoding
 * @{
 */
typedef struct AVInputFormat {
    /**
     * A comma separated list of short names for the format. New names
     * may be appended with a minor bump.
     */
    const char *name;

    /**
     * Descriptive name for the format, meant to be more human-readable
     * than name. You should use the NULL_IF_CONFIG_SMALL() macro
     * to define it.
     */
    const char *long_name;

    /**
     * Can use flags: AVFMT_NOFILE, AVFMT_NEEDNUMBER, AVFMT_SHOW_IDS,
     * AVFMT_GENERIC_INDEX, AVFMT_TS_DISCONT, AVFMT_NOBINSEARCH,
     * AVFMT_NOGENSEARCH, AVFMT_NO_BYTE_SEEK, AVFMT_SEEK_TO_PTS.
     */
    int flags;

    /**
     * If extensions are defined, then no probe is done. You should
     * usually not use extension format guessing because it is not
     * reliable enough
     */
    const char *extensions;

    const struct AVCodecTag * const *codec_tag;

    const AVClass *priv_class; ///< AVClass for the private context

    /*****************************************************************
     * No fields below this line are part of the public API. They
     * may not be used outside of libavformat and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */
    struct AVInputFormat *next;

    /**
     * Raw demuxers store their codec ID here.
     */
    int raw_codec_id;

    /**
     * Size of private data so that it can be allocated in the wrapper.
     */
    int priv_data_size;

    /**
     * Tell if a given file has a chance of being parsed as this format.
     * The buffer provided is guaranteed to be AVPROBE_PADDING_SIZE bytes
     * big so you do not have to check for that unless you need more.
     */
    int (*read_probe)(AVProbeData *);

    /**
     * Read the format header and initialize the AVFormatContext
     * structure. Return 0 if OK. Only used in raw format right
     * now. 'avformat_new_stream' should be called to create new streams.
     */
    int (*read_header)(struct AVFormatContext *);

    /**
     * Read one packet and put it in 'pkt'. pts and flags are also
     * set. 'avformat_new_stream' can be called only if the flag
     * AVFMTCTX_NOHEADER is used and only in the calling thread (not in a
     * background thread).
     * @return 0 on success, < 0 on error.
     *         When returning an error, pkt must not have been allocated
     *         or must be freed before returning
     */
    int (*read_packet)(struct AVFormatContext *, AVPacket *pkt);

    /**
     * Close the stream. The AVFormatContext and AVStreams are not
     * freed by this function
     */
    int (*read_close)(struct AVFormatContext *);

    /**
     * Seek to a given timestamp relative to the frames in
     * stream component stream_index.
     * @param stream_index Must not be -1.
     * @param flags Selects which direction should be preferred if no exact
     *              match is available.
     * @return >= 0 on success (but not necessarily the new offset)
     */
    int (*read_seek)(struct AVFormatContext *,
                     int stream_index, int64_t timestamp, int flags);

    /**
     * Get the next timestamp in stream[stream_index].time_base units.
     * @return the timestamp or AV_NOPTS_VALUE if an error occurred
     */
    int64_t (*read_timestamp)(struct AVFormatContext *s, int stream_index,
                              int64_t *pos, int64_t pos_limit);

    /**
     * Start/resume playing - only meaningful if using a network-based format
     * (RTSP).
     */
    int (*read_play)(struct AVFormatContext *);

    /**
     * Pause playing - only meaningful if using a network-based format
     * (RTSP).
     */
    int (*read_pause)(struct AVFormatContext *);

    /**
     * Seek to timestamp ts.
     * Seeking will be done so that the point from which all active streams
     * can be presented successfully will be closest to ts and within min/max_ts.
     * Active streams are all streams that have AVStream.discard < AVDISCARD_ALL.
     */
    int (*read_seek2)(struct AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags);
} AVInputFormat;
/**
 * @}
 */

enum AVStreamParseType {
    AVSTREAM_PARSE_NONE,
    AVSTREAM_PARSE_FULL,       /**< full parsing and repack */
    AVSTREAM_PARSE_HEADERS,    /**< Only parse headers, do not repack. */
    AVSTREAM_PARSE_TIMESTAMPS, /**< full parsing and interpolation of timestamps for frames not starting on a packet boundary */
    AVSTREAM_PARSE_FULL_ONCE,  /**< full parsing and repack of the first frame only, only implemented for H.264 currently */
    AVSTREAM_PARSE_FULL_RAW=MKTAG(0,'R','A','W'),       /**< full parsing and repack with timestamp and position generation by parser for raw
                                                             this assumes that each packet in the file contains no demuxer level headers and
                                                             just codec level data, otherwise position generation would fail */
};

typedef struct AVIndexEntry {
    int64_t pos;
    int64_t timestamp;        /**<
                               * Timestamp in AVStream.time_base units, preferably the time from which on correctly decoded frames are available
                               * when seeking to this entry. That means preferable PTS on keyframe based formats.
                               * But demuxers can choose to store a different timestamp, if it is more convenient for the implementation or nothing better
                               * is known
                               */
#define AVINDEX_KEYFRAME 0x0001
    int flags:2;
    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).
    int min_distance;         /**< Minimum distance between this and the previous keyframe, used to avoid unneeded searching. */
} AVIndexEntry;

#define AV_DISPOSITION_DEFAULT   0x0001
#define AV_DISPOSITION_DUB       0x0002
#define AV_DISPOSITION_ORIGINAL  0x0004
#define AV_DISPOSITION_COMMENT   0x0008
#define AV_DISPOSITION_LYRICS    0x0010
#define AV_DISPOSITION_KARAOKE   0x0020

/**
 * Track should be used during playback by default.
 * Useful for subtitle track that should be displayed
 * even when user did not explicitly ask for subtitles.
 */
#define AV_DISPOSITION_FORCED    0x0040
#define AV_DISPOSITION_HEARING_IMPAIRED  0x0080  /**< stream for hearing impaired audiences */
#define AV_DISPOSITION_VISUAL_IMPAIRED   0x0100  /**< stream for visual impaired audiences */
#define AV_DISPOSITION_CLEAN_EFFECTS     0x0200  /**< stream without voice */
/**
 * The stream is stored in the file as an attached picture/"cover art" (e.g.
 * APIC frame in ID3v2). The single packet associated with it will be returned
 * among the first few packets read from the file unless seeking takes place.
 * It can also be accessed at any time in AVStream.attached_pic.
 */
#define AV_DISPOSITION_ATTACHED_PIC      0x0400

/**
 * To specify text track kind (different from subtitles default).
 */
#define AV_DISPOSITION_CAPTIONS     0x10000
#define AV_DISPOSITION_DESCRIPTIONS 0x20000
#define AV_DISPOSITION_METADATA     0x40000

/**
 * Options for behavior on timestamp wrap detection.
 */
#define AV_PTS_WRAP_IGNORE      0   ///< ignore the wrap
#define AV_PTS_WRAP_ADD_OFFSET  1   ///< add the format specific offset on wrap detection
#define AV_PTS_WRAP_SUB_OFFSET  -1  ///< subtract the format specific offset on wrap detection

/**
 * Stream structure.
 * New fields can be added to the end with minor version bumps.
 * Removal, reordering and changes to existing fields require a major
 * version bump.
 * sizeof(AVStream) must not be used outside libav*.
 */
typedef struct AVStream {
    int index;    /**< stream index in AVFormatContext */
    /**
     * Format-specific stream ID.
     * decoding: set by libavformat
     * encoding: set by the user, replaced by libavformat if left unset
     */
    int id;
    /**
     * Codec context associated with this stream. Allocated and freed by
     * libavformat.
     *
     * - decoding: The demuxer exports codec information stored in the headers
     *             here.
     * - encoding: The user sets codec information, the muxer writes it to the
     *             output. Mandatory fields as specified in AVCodecContext
     *             documentation must be set even if this AVCodecContext is
     *             not actually used for encoding.
     */
    AVCodecContext *codec;
    void *priv_data;

    /**
     * encoding: pts generation when outputting stream
     */
    struct AVFrac pts;

    /**
     * This is the fundamental unit of time (in seconds) in terms
     * of which frame timestamps are represented.
     *
     * decoding: set by libavformat
     * encoding: set by libavformat in avformat_write_header. The muxer may use the
     * user-provided value of @ref AVCodecContext.time_base "codec->time_base"
     * as a hint.
     */
    AVRational time_base;

    /**
     * Decoding: pts of the first frame of the stream in presentation order, in stream time base.
     * Only set this if you are absolutely 100% sure that the value you set
     * it to really is the pts of the first frame.
     * This may be undefined (AV_NOPTS_VALUE).
     * @note The ASF header does NOT contain a correct start_time the ASF
     * demuxer must NOT set this.
     */
    int64_t start_time;

    /**
     * Decoding: duration of the stream, in stream time base.
     * If a source file does not specify a duration, but does specify
     * a bitrate, this value will be estimated from bitrate and file size.
     */
    int64_t duration;

    int64_t nb_frames;                 ///< number of frames in this stream if known or 0

    int disposition; /**< AV_DISPOSITION_* bit field */

    enum AVDiscard discard; ///< Selects which packets can be discarded at will and do not need to be demuxed.

    /**
     * sample aspect ratio (0 if unknown)
     * - encoding: Set by user.
     * - decoding: Set by libavformat.
     */
    AVRational sample_aspect_ratio;

    AVDictionary *metadata;

    /**
     * Average framerate
     */
    AVRational avg_frame_rate;

    /**
     * For streams with AV_DISPOSITION_ATTACHED_PIC disposition, this packet
     * will contain the attached picture.
     *
     * decoding: set by libavformat, must not be modified by the caller.
     * encoding: unused
     */
    AVPacket attached_pic;

    /*****************************************************************
     * All fields below this line are not part of the public API. They
     * may not be used outside of libavformat and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */

    /**
     * Stream information used internally by av_find_stream_info()
     */
#define MAX_STD_TIMEBASES (60*12+6)
    struct {
        int64_t last_dts;
        int64_t duration_gcd;
        int duration_count;
        int64_t rfps_duration_sum;
        double (*duration_error)[2][MAX_STD_TIMEBASES];
        int64_t codec_info_duration;
        int64_t codec_info_duration_fields;
        int found_decoder;

        int64_t last_duration;

        /**
         * Those are used for average framerate estimation.
         */
        int64_t fps_first_dts;
        int     fps_first_dts_idx;
        int64_t fps_last_dts;
        int     fps_last_dts_idx;

    } *info;

    int pts_wrap_bits; /**< number of bits in pts (used for wrapping control) */

#if FF_API_REFERENCE_DTS
    /* a hack to keep ABI compatibility for ffmpeg and other applications, which accesses parser even
     * though it should not */
    int64_t do_not_use;
#endif
    // Timestamp generation support:
    /**
     * Timestamp corresponding to the last dts sync point.
     *
     * Initialized when AVCodecParserContext.dts_sync_point >= 0 and
     * a DTS is received from the underlying container. Otherwise set to
     * AV_NOPTS_VALUE by default.
     */
    int64_t first_dts;
    int64_t cur_dts;
    int64_t last_IP_pts;
    int last_IP_duration;

    /**
     * Number of packets to buffer for codec probing
     */
#define MAX_PROBE_PACKETS 2500
    int probe_packets;

    /**
     * Number of frames that have been demuxed during av_find_stream_info()
     */
    int codec_info_nb_frames;

    /* av_read_frame() support */
    enum AVStreamParseType need_parsing;
    struct AVCodecParserContext *parser;

    /**
     * last packet in packet_buffer for this stream when muxing.
     */
    struct AVPacketList *last_in_packet_buffer;
    AVProbeData probe_data;
#define MAX_REORDER_DELAY 16
    int64_t pts_buffer[MAX_REORDER_DELAY+1];

    AVIndexEntry *index_entries; /**< Only used if the format does not
                                    support seeking natively. */
    int nb_index_entries;
    unsigned int index_entries_allocated_size;

    /**
     * Real base framerate of the stream.
     * This is the lowest framerate with which all timestamps can be
     * represented accurately (it is the least common multiple of all
     * framerates in the stream). Note, this value is just a guess!
     * For example, if the time base is 1/90000 and all frames have either
     * approximately 3600 or 1800 timer ticks, then r_frame_rate will be 50/1.
     *
     * Code outside avformat should access this field using:
     * av_stream_get/set_r_frame_rate(stream)
     */
    AVRational r_frame_rate;

    /**
     * Stream Identifier
     * This is the MPEG-TS stream identifier +1
     * 0 means unknown
     */
    int stream_identifier;

    int64_t interleaver_chunk_size;
    int64_t interleaver_chunk_duration;

    /**
     * stream probing state
     * -1   -> probing finished
     *  0   -> no probing requested
     * rest -> perform probing with request_probe being the minimum score to accept.
     * NOT PART OF PUBLIC API
     */
    int request_probe;
    /**
     * Indicates that everything up to the next keyframe
     * should be discarded.
     */
    int skip_to_keyframe;

    /**
     * Number of samples to skip at the start of the frame decoded from the next packet.
     */
    int skip_samples;

    /**
     * Number of internally decoded frames, used internally in libavformat, do not access
     * its lifetime differs from info which is why it is not in that structure.
     */
    int nb_decoded_frames;

    /**
     * Timestamp offset added to timestamps before muxing
     * NOT PART OF PUBLIC API
     */
    int64_t mux_ts_offset;

    /**
     * Internal data to check for wrapping of the time stamp
     */
    int64_t pts_wrap_reference;

    /**
     * Options for behavior, when a wrap is detected.
     *
     * Defined by AV_PTS_WRAP_ values.
     *
     * If correction is enabled, there are two possibilities:
     * If the first time stamp is near the wrap point, the wrap offset
     * will be subtracted, which will create negative time stamps.
     * Otherwise the offset will be added.
     */
    int pts_wrap_behavior;

    /**
     * Internal data to prevent doing update_initial_durations() twice
     */
    int update_initial_durations_done;
} AVStream;

AVRational av_stream_get_r_frame_rate(const AVStream *s);
void       av_stream_set_r_frame_rate(AVStream *s, AVRational r);

#define AV_PROGRAM_RUNNING 1

/**
 * New fields can be added to the end with minor version bumps.
 * Removal, reordering and changes to existing fields require a major
 * version bump.
 * sizeof(AVProgram) must not be used outside libav*.
 */
typedef struct AVProgram {
    int            id;
    int            flags;
    enum AVDiscard discard;        ///< selects which program to discard and which to feed to the caller
    unsigned int   *stream_index;
    unsigned int   nb_stream_indexes;
    AVDictionary *metadata;

    int program_num;
    int pmt_pid;
    int pcr_pid;

    /*****************************************************************
     * All fields below this line are not part of the public API. They
     * may not be used outside of libavformat and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */
    int64_t start_time;
    int64_t end_time;

    int64_t pts_wrap_reference;    ///< reference dts for wrap detection
    int pts_wrap_behavior;         ///< behavior on wrap detection
} AVProgram;

#define AVFMTCTX_NOHEADER      0x0001 /**< signal that no header is present
                                         (streams are added dynamically) */

typedef struct AVChapter {
    int id;                 ///< unique ID to identify the chapter
    AVRational time_base;   ///< time base in which the start/end timestamps are specified
    int64_t start, end;     ///< chapter start/end time in time_base units
    AVDictionary *metadata;
} AVChapter;


/**
 * Callback used by devices to communicate with application.
 */
typedef int (*av_format_control_message)(struct AVFormatContext *s, int type,
                                         void *data, size_t data_size);


/**
 * The duration of a video can be estimated through various ways, and this enum can be used
 * to know how the duration was estimated.
 */
enum AVDurationEstimationMethod {
    AVFMT_DURATION_FROM_PTS,    ///< Duration accurately estimated from PTSes
    AVFMT_DURATION_FROM_STREAM, ///< Duration estimated from a stream with a known duration
    AVFMT_DURATION_FROM_BITRATE ///< Duration estimated from bitrate (less accurate)
};

typedef struct AVFormatInternal AVFormatInternal;

/**
 * Format I/O context.
 * New fields can be added to the end with minor version bumps.
 * Removal, reordering and changes to existing fields require a major
 * version bump.
 * sizeof(AVFormatContext) must not be used outside libav*, use
 * avformat_alloc_context() to create an AVFormatContext.
 */
typedef struct AVFormatContext {
    /**
     * A class for logging and @ref avoptions. Set by avformat_alloc_context().
     * Exports (de)muxer private options if they exist.
     */
    const AVClass *av_class;

    /**
     * The input container format.
     *
     * Demuxing only, set by avformat_open_input().
     */
    struct AVInputFormat *iformat;

    /**
     * The output container format.
     *
     * Muxing only, must be set by the caller before avformat_write_header().
     */
    struct AVOutputFormat *oformat;

    /**
     * Format private data. This is an AVOptions-enabled struct
     * if and only if iformat/oformat.priv_class is not NULL.
     *
     * - muxing: set by avformat_write_header()
     * - demuxing: set by avformat_open_input()
     */
    void *priv_data;

    /**
     * I/O context.
     *
     * - demuxing: either set by the user before avformat_open_input() (then
     *             the user must close it manually) or set by avformat_open_input().
     * - muxing: set by the user before avformat_write_header(). The caller must
     *           take care of closing / freeing the IO context.
     *
     * Do NOT set this field if AVFMT_NOFILE flag is set in
     * iformat/oformat.flags. In such a case, the (de)muxer will handle
     * I/O in some other way and this field will be NULL.
     */
    AVIOContext *pb;

    /* stream info */
    int ctx_flags; /**< Format-specific flags, see AVFMTCTX_xx */

    /**
     * Number of elements in AVFormatContext.streams.
     *
     * Set by avformat_new_stream(), must not be modified by any other code.
     */
    unsigned int nb_streams;
    /**
     * A list of all streams in the file. New streams are created with
     * avformat_new_stream().
     *
     * - demuxing: streams are created by libavformat in avformat_open_input().
     *             If AVFMTCTX_NOHEADER is set in ctx_flags, then new streams may also
     *             appear in av_read_frame().
     * - muxing: streams are created by the user before avformat_write_header().
     *
     * Freed by libavformat in avformat_free_context().
     */
    AVStream **streams;

    /**
     * input or output filename
     *
     * - demuxing: set by avformat_open_input()
     * - muxing: may be set by the caller before avformat_write_header()
     */
    char filename[1024];

    /**
     * Position of the first frame of the component, in
     * AV_TIME_BASE fractional seconds. NEVER set this value directly:
     * It is deduced from the AVStream values.
     *
     * Demuxing only, set by libavformat.
     */
    int64_t start_time;

    /**
     * Duration of the stream, in AV_TIME_BASE fractional
     * seconds. Only set this value if you know none of the individual stream
     * durations and also do not set any of them. This is deduced from the
     * AVStream values if not set.
     *
     * Demuxing only, set by libavformat.
     */
    int64_t duration;

    /**
     * Total stream bitrate in bit/s, 0 if not
     * available. Never set it directly if the file_size and the
     * duration are known as FFmpeg can compute it automatically.
     */
    int bit_rate;

    unsigned int packet_size;
    int max_delay;

    int flags;
#define AVFMT_FLAG_GENPTS       0x0001 ///< Generate missing pts even if it requires parsing future frames.
#define AVFMT_FLAG_IGNIDX       0x0002 ///< Ignore index.
#define AVFMT_FLAG_NONBLOCK     0x0004 ///< Do not block when reading packets from input.
#define AVFMT_FLAG_IGNDTS       0x0008 ///< Ignore DTS on frames that contain both DTS & PTS
#define AVFMT_FLAG_NOFILLIN     0x0010 ///< Do not infer any values from other values, just return what is stored in the container
#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
#define AVFMT_FLAG_NOBUFFER     0x0040 ///< Do not buffer frames when possible
#define AVFMT_FLAG_CUSTOM_IO    0x0080 ///< The caller has supplied a custom AVIOContext, don't avio_close() it.
#define AVFMT_FLAG_DISCARD_CORRUPT  0x0100 ///< Discard frames marked corrupted
#define AVFMT_FLAG_FLUSH_PACKETS    0x0200 ///< Flush the AVIOContext every packet.
#define AVFMT_FLAG_MP4A_LATM    0x8000 ///< Enable RTP MP4A-LATM payload
#define AVFMT_FLAG_SORT_DTS    0x10000 ///< try to interleave outputted packets by dts (using this flag can slow demuxing down)
#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)
#define AVFMT_FLAG_KEEP_SIDE_DATA 0x40000 ///< Don't merge side data but keep it separate.

    /**
     * Maximum size of the data read from input for determining
     * the input container format.
     * Demuxing only, set by the caller before avformat_open_input().
     */
    unsigned int probesize;

    /**
     * Maximum duration (in AV_TIME_BASE units) of the data read
     * from input in avformat_find_stream_info().
     * Demuxing only, set by the caller before avformat_find_stream_info().
     */
    int max_analyze_duration;

    const uint8_t *key;
    int keylen;

    unsigned int nb_programs;
    AVProgram **programs;

    /**
     * Forced video codec_id.
     * Demuxing: Set by user.
     */
    enum AVCodecID video_codec_id;

    /**
     * Forced audio codec_id.
     * Demuxing: Set by user.
     */
    enum AVCodecID audio_codec_id;

    /**
     * Forced subtitle codec_id.
     * Demuxing: Set by user.
     */
    enum AVCodecID subtitle_codec_id;

    /**
     * Maximum amount of memory in bytes to use for the index of each stream.
     * If the index exceeds this size, entries will be discarded as
     * needed to maintain a smaller size. This can lead to slower or less
     * accurate seeking (depends on demuxer).
     * Demuxers for which a full in-memory index is mandatory will ignore
     * this.
     * - muxing: unused
     * - demuxing: set by user
     */
    unsigned int max_index_size;

    /**
     * Maximum amount of memory in bytes to use for buffering frames
     * obtained from realtime capture devices.
     */
    unsigned int max_picture_buffer;

    /**
     * Number of chapters in AVChapter array.
     * When muxing, chapters are normally written in the file header,
     * so nb_chapters should normally be initialized before write_header
     * is called. Some muxers (e.g. mov and mkv) can also write chapters
     * in the trailer.  To write chapters in the trailer, nb_chapters
     * must be zero when write_header is called and non-zero when
     * write_trailer is called.
     * - muxing: set by user
     * - demuxing: set by libavformat
     */
    unsigned int nb_chapters;
    AVChapter **chapters;

    /**
     * Metadata that applies to the whole file.
     *
     * - demuxing: set by libavformat in avformat_open_input()
     * - muxing: may be set by the caller before avformat_write_header()
     *
     * Freed by libavformat in avformat_free_context().
     */
    AVDictionary *metadata;

    /**
     * Start time of the stream in real world time, in microseconds
     * since the Unix epoch (00:00 1st January 1970). That is, pts=0 in the
     * stream was captured at this real world time.
     * Muxing only, set by the caller before avformat_write_header().
     */
    int64_t start_time_realtime;

    /**
     * The number of frames used for determining the framerate in
     * avformat_find_stream_info().
     * Demuxing only, set by the caller before avformat_find_stream_info().
     */
    int fps_probe_size;

    /**
     * Error recognition; higher values will detect more errors but may
     * misdetect some more or less valid parts as errors.
     * Demuxing only, set by the caller before avformat_open_input().
     */
    int error_recognition;

    /**
     * Custom interrupt callbacks for the I/O layer.
     *
     * demuxing: set by the user before avformat_open_input().
     * muxing: set by the user before avformat_write_header()
     * (mainly useful for AVFMT_NOFILE formats). The callback
     * should also be passed to avio_open2() if it's used to
     * open the file.
     */
    AVIOInterruptCB interrupt_callback;

    /**
     * Flags to enable debugging.
     */
    int debug;
#define FF_FDEBUG_TS        0x0001

    /**
     * Maximum buffering duration for interleaving.
     *
     * To ensure all the streams are interleaved correctly,
     * av_interleaved_write_frame() will wait until it has at least one packet
     * for each stream before actually writing any packets to the output file.
     * When some streams are "sparse" (i.e. there are large gaps between
     * successive packets), this can result in excessive buffering.
     *
     * This field specifies the maximum difference between the timestamps of the
     * first and the last packet in the muxing queue, above which libavformat
     * will output a packet regardless of whether it has queued a packet for all
     * the streams.
     *
     * Muxing only, set by the caller before avformat_write_header().
     */
    int64_t max_interleave_delta;

    /**
     * Transport stream id.
     * This will be moved into demuxer private options. Thus no API/ABI compatibility
     */
    int ts_id;

    /**
     * Audio preload in microseconds.
     * Note, not all formats support this and unpredictable things may happen if it is used when not supported.
     * - encoding: Set by user via AVOptions (NO direct access)
     * - decoding: unused
     */
    int audio_preload;

    /**
     * Max chunk time in microseconds.
     * Note, not all formats support this and unpredictable things may happen if it is used when not supported.
     * - encoding: Set by user via AVOptions (NO direct access)
     * - decoding: unused
     */
    int max_chunk_duration;

    /**
     * Max chunk size in bytes
     * Note, not all formats support this and unpredictable things may happen if it is used when not supported.
     * - encoding: Set by user via AVOptions (NO direct access)
     * - decoding: unused
     */
    int max_chunk_size;

    /**
     * forces the use of wallclock timestamps as pts/dts of packets
     * This has undefined results in the presence of B frames.
     * - encoding: unused
     * - decoding: Set by user via AVOptions (NO direct access)
     */
    int use_wallclock_as_timestamps;

    /**
     * Avoid negative timestamps during muxing.
     *  0 -> allow negative timestamps
     *  1 -> avoid negative timestamps
     * -1 -> choose automatically (default)
     * Note, this only works when interleave_packet_per_dts is in use.
     * - encoding: Set by user via AVOptions (NO direct access)
     * - decoding: unused
     */
    int avoid_negative_ts;

    /**
     * avio flags, used to force AVIO_FLAG_DIRECT.
     * - encoding: unused
     * - decoding: Set by user via AVOptions (NO direct access)
     */
    int avio_flags;

    /**
     * The duration field can be estimated through various ways, and this field can be used
     * to know how the duration was estimated.
     * - encoding: unused
     * - decoding: Read by user via AVOptions (NO direct access)
     */
    enum AVDurationEstimationMethod duration_estimation_method;

    /**
     * Skip initial bytes when opening stream
     * - encoding: unused
     * - decoding: Set by user via AVOptions (NO direct access)
     */
    unsigned int skip_initial_bytes;

    /**
     * Correct single timestamp overflows
     * - encoding: unused
     * - decoding: Set by user via AVOptions (NO direct access)
     */
    unsigned int correct_ts_overflow;

    /**
     * Force seeking to any (also non key) frames.
     * - encoding: unused
     * - decoding: Set by user via AVOptions (NO direct access)
     */
    int seek2any;

    /**
     * Flush the I/O context after each packet.
     * - encoding: Set by user via AVOptions (NO direct access)
     * - decoding: unused
     */
    int flush_packets;

    /**
     * format probing score.
     * The maximal score is AVPROBE_SCORE_MAX, its set when the demuxer probes
     * the format.
     * - encoding: unused
     * - decoding: set by avformat, read by user via av_format_get_probe_score() (NO direct access)
     */
    int probe_score;

    /*****************************************************************
     * All fields below this line are not part of the public API. They
     * may not be used outside of libavformat and can be changed and
     * removed at will.
     * New public fields should be added right above.
     *****************************************************************
     */

    /**
     * This buffer is only needed when packets were already buffered but
     * not decoded, for example to get the codec parameters in MPEG
     * streams.
     */
    struct AVPacketList *packet_buffer;
    struct AVPacketList *packet_buffer_end;

    /* av_seek_frame() support */
    int64_t data_offset; /**< offset of the first packet */

    /**
     * Raw packets from the demuxer, prior to parsing and decoding.
     * This buffer is used for buffering packets until the codec can
     * be identified, as parsing cannot be done without knowing the
     * codec.
     */
    struct AVPacketList *raw_packet_buffer;
    struct AVPacketList *raw_packet_buffer_end;
    /**
     * Packets split by the parser get queued here.
     */
    struct AVPacketList *parse_queue;
    struct AVPacketList *parse_queue_end;
    /**
     * Remaining size available for raw_packet_buffer, in bytes.
     */
#define RAW_PACKET_BUFFER_SIZE 2500000
    int raw_packet_buffer_remaining_size;

    /**
     * Offset to remap timestamps to be non-negative.
     * Expressed in timebase units.
     * @see AVStream.mux_ts_offset
     */
    int64_t offset;

    /**
     * Timebase for the timestamp offset.
     */
    AVRational offset_timebase;

    /**
     * An opaque field for libavformat internal usage.
     * Must not be accessed in any way by callers.
     */
    AVFormatInternal *internal;

    /**
     * IO repositioned flag.
     * This is set by avformat when the underlaying IO context read pointer
     * is repositioned, for example when doing byte based seeking.
     * Demuxers can use the flag to detect such changes.
     */
    int io_repositioned;

    /**
     * Forced video codec.
     * This allows forcing a specific decoder, even when there are multiple with
     * the same codec_id.
     * Demuxing: Set by user via av_format_set_video_codec (NO direct access).
     */
    AVCodec *video_codec;

    /**
     * Forced audio codec.
     * This allows forcing a specific decoder, even when there are multiple with
     * the same codec_id.
     * Demuxing: Set by user via av_format_set_audio_codec (NO direct access).
     */
    AVCodec *audio_codec;

    /**
     * Forced subtitle codec.
     * This allows forcing a specific decoder, even when there are multiple with
     * the same codec_id.
     * Demuxing: Set by user via av_format_set_subtitle_codec (NO direct access).
     */
    AVCodec *subtitle_codec;

    /**
     * Number of bytes to be written as padding in a metadata header.
     * Demuxing: Unused.
     * Muxing: Set by user via av_format_set_metadata_header_padding.
     */
    int metadata_header_padding;

    /**
     * User data.
     * This is a place for some private data of the user.
     * Mostly usable with control_message_cb or any future callbacks in device's context.
     */
    void *opaque;

    /**
     * Callback used by devices to communicate with application.
     */
    av_format_control_message control_message_cb;

    /**
     * Output timestamp offset, in microseconds.
     * Muxing: set by user via AVOptions (NO direct access)
     */
    int64_t output_ts_offset;
} AVFormatContext;

int av_format_get_probe_score(const AVFormatContext *s);
AVCodec * av_format_get_video_codec(const AVFormatContext *s);
void      av_format_set_video_codec(AVFormatContext *s, AVCodec *c);
AVCodec * av_format_get_audio_codec(const AVFormatContext *s);
void      av_format_set_audio_codec(AVFormatContext *s, AVCodec *c);
AVCodec * av_format_get_subtitle_codec(const AVFormatContext *s);
void      av_format_set_subtitle_codec(AVFormatContext *s, AVCodec *c);
int       av_format_get_metadata_header_padding(const AVFormatContext *s);
void      av_format_set_metadata_header_padding(AVFormatContext *s, int c);
void *    av_format_get_opaque(const AVFormatContext *s);
void      av_format_set_opaque(AVFormatContext *s, void *opaque);
av_format_control_message av_format_get_control_message_cb(const AVFormatContext *s);
void      av_format_set_control_message_cb(AVFormatContext *s, av_format_control_message callback);

/**
 * Returns the method used to set ctx->duration.
 *
 * @return AVFMT_DURATION_FROM_PTS, AVFMT_DURATION_FROM_STREAM, or AVFMT_DURATION_FROM_BITRATE.
 */
enum AVDurationEstimationMethod av_fmt_ctx_get_duration_estimation_method(const AVFormatContext* ctx);

typedef struct AVPacketList {
    AVPacket pkt;
    struct AVPacketList *next;
} AVPacketList;


/**
 * @defgroup lavf_core Core functions
 * @ingroup libavf
 *
 * Functions for querying libavformat capabilities, allocating core structures,
 * etc.
 * @{
 */

/**
 * Return the LIBAVFORMAT_VERSION_INT constant.
 */
unsigned avformat_version(void);

/**
 * Return the libavformat build-time configuration.
 */
const char *avformat_configuration(void);

/**
 * Return the libavformat license.
 */
const char *avformat_license(void);

/**
 * Initialize libavformat and register all the muxers, demuxers and
 * protocols. If you do not call this function, then you can select
 * exactly which formats you want to support.
 *
 * @see av_register_input_format()
 * @see av_register_output_format()
 */
void av_register_all(void);

void av_register_input_format(AVInputFormat *format);
void av_register_output_format(AVOutputFormat *format);

/**
 * Do global initialization of network components. This is optional,
 * but recommended, since it avoids the overhead of implicitly
 * doing the setup for each session.
 *
 * Calling this function will become mandatory if using network
 * protocols at some major version bump.
 */
int avformat_network_init(void);

/**
 * Undo the initialization done by avformat_network_init.
 */
int avformat_network_deinit(void);

/**
 * If f is NULL, returns the first registered input format,
 * if f is non-NULL, returns the next registered input format after f
 * or NULL if f is the last one.
 */
AVInputFormat  *av_iformat_next(AVInputFormat  *f);

/**
 * If f is NULL, returns the first registered output format,
 * if f is non-NULL, returns the next registered output format after f
 * or NULL if f is the last one.
 */
AVOutputFormat *av_oformat_next(AVOutputFormat *f);

/**
 * Allocate an AVFormatContext.
 * avformat_free_context() can be used to free the context and everything
 * allocated by the framework within it.
 */
AVFormatContext *avformat_alloc_context(void);

/**
 * Free an AVFormatContext and all its streams.
 * @param s context to free
 */
void avformat_free_context(AVFormatContext *s);

/**
 * Get the AVClass for AVFormatContext. It can be used in combination with
 * AV_OPT_SEARCH_FAKE_OBJ for examining options.
 *
 * @see av_opt_find().
 */
const AVClass *avformat_get_class(void);

/**
 * Add a new stream to a media file.
 *
 * When demuxing, it is called by the demuxer in read_header(). If the
 * flag AVFMTCTX_NOHEADER is set in s.ctx_flags, then it may also
 * be called in read_packet().
 *
 * When muxing, should be called by the user before avformat_write_header().
 *
 * User is required to call avcodec_close() and avformat_free_context() to
 * clean up the allocation by avformat_new_stream().
 *
 * @param c If non-NULL, the AVCodecContext corresponding to the new stream
 * will be initialized to use this codec. This is needed for e.g. codec-specific
 * defaults to be set, so codec should be provided if it is known.
 *
 * @return newly created stream or NULL on error.
 */
AVStream *avformat_new_stream(AVFormatContext *s, const AVCodec *c);

AVProgram *av_new_program(AVFormatContext *s, int id);

/**
 * @}
 */


#if FF_API_ALLOC_OUTPUT_CONTEXT
/**
 * @deprecated deprecated in favor of avformat_alloc_output_context2()
 */
attribute_deprecated
AVFormatContext *avformat_alloc_output_context(const char *format,
                                               AVOutputFormat *oformat,
                                               const char *filename);
#endif

/**
 * Allocate an AVFormatContext for an output format.
 * avformat_free_context() can be used to free the context and
 * everything allocated by the framework within it.
 *
 * @param *ctx is set to the created format context, or to NULL in
 * case of failure
 * @param oformat format to use for allocating the context, if NULL
 * format_name and filename are used instead
 * @param format_name the name of output format to use for allocating the
 * context, if NULL filename is used instead
 * @param filename the name of the filename to use for allocating the
 * context, may be NULL
 * @return >= 0 in case of success, a negative AVERROR code in case of
 * failure
 */
int avformat_alloc_output_context2(AVFormatContext **ctx, AVOutputFormat *oformat,
                                   const char *format_name, const char *filename);

/**
 * @addtogroup lavf_decoding
 * @{
 */

/**
 * Find AVInputFormat based on the short name of the input format.
 */
AVInputFormat *av_find_input_format(const char *short_name);

/**
 * Guess the file format.
 *
 * @param is_opened Whether the file is already opened; determines whether
 *                  demuxers with or without AVFMT_NOFILE are probed.
 */
AVInputFormat *av_probe_input_format(AVProbeData *pd, int is_opened);

/**
 * Guess the file format.
 *
 * @param is_opened Whether the file is already opened; determines whether
 *                  demuxers with or without AVFMT_NOFILE are probed.
 * @param score_max A probe score larger that this is required to accept a
 *                  detection, the variable is set to the actual detection
 *                  score afterwards.
 *                  If the score is <= AVPROBE_SCORE_MAX / 4 it is recommended
 *                  to retry with a larger probe buffer.
 */
AVInputFormat *av_probe_input_format2(AVProbeData *pd, int is_opened, int *score_max);

/**
 * Guess the file format.
 *
 * @param is_opened Whether the file is already opened; determines whether
 *                  demuxers with or without AVFMT_NOFILE are probed.
 * @param score_ret The score of the best detection.
 */
AVInputFormat *av_probe_input_format3(AVProbeData *pd, int is_opened, int *score_ret);

/**
 * Probe a bytestream to determine the input format. Each time a probe returns
 * with a score that is too low, the probe buffer size is increased and another
 * attempt is made. When the maximum probe size is reached, the input format
 * with the highest score is returned.
 *
 * @param pb the bytestream to probe
 * @param fmt the input format is put here
 * @param filename the filename of the stream
 * @param logctx the log context
 * @param offset the offset within the bytestream to probe from
 * @param max_probe_size the maximum probe buffer size (zero for default)
 * @return the score in case of success, a negative value corresponding to an
 *         the maximal score is AVPROBE_SCORE_MAX
 * AVERROR code otherwise
 */
int av_probe_input_buffer2(AVIOContext *pb, AVInputFormat **fmt,
                           const char *filename, void *logctx,
                           unsigned int offset, unsigned int max_probe_size);

/**
 * Like av_probe_input_buffer2() but returns 0 on success
 */
int av_probe_input_buffer(AVIOContext *pb, AVInputFormat **fmt,
                          const char *filename, void *logctx,
                          unsigned int offset, unsigned int max_probe_size);

/**
 * Open an input stream and read the header. The codecs are not opened.
 * The stream must be closed with avformat_close_input().
 *
 * @param ps Pointer to user-supplied AVFormatContext (allocated by avformat_alloc_context).
 *           May be a pointer to NULL, in which case an AVFormatContext is allocated by this
 *           function and written into ps.
 *           Note that a user-supplied AVFormatContext will be freed on failure.
 * @param filename Name of the stream to open.
 * @param fmt If non-NULL, this parameter forces a specific input format.
 *            Otherwise the format is autodetected.
 * @param options  A dictionary filled with AVFormatContext and demuxer-private options.
 *                 On return this parameter will be destroyed and replaced with a dict containing
 *                 options that were not found. May be NULL.
 *
 * @return 0 on success, a negative AVERROR on failure.
 *
 * @note If you want to use custom IO, preallocate the format context and set its pb field.
 */
int avformat_open_input(AVFormatContext **ps, const char *filename, AVInputFormat *fmt, AVDictionary **options);

attribute_deprecated
int av_demuxer_open(AVFormatContext *ic);

#if FF_API_FORMAT_PARAMETERS
/**
 * Read packets of a media file to get stream information. This
 * is useful for file formats with no headers such as MPEG. This
 * function also computes the real framerate in case of MPEG-2 repeat
 * frame mode.
 * The logical file position is not changed by this function;
 * examined packets may be buffered for later processing.
 *
 * @param ic media file handle
 * @return >=0 if OK, AVERROR_xxx on error
 * @todo Let the user decide somehow what information is needed so that
 *       we do not waste time getting stuff the user does not need.
 *
 * @deprecated use avformat_find_stream_info.
 */
attribute_deprecated
int av_find_stream_info(AVFormatContext *ic);
#endif

/**
 * Read packets of a media file to get stream information. This
 * is useful for file formats with no headers such as MPEG. This
 * function also computes the real framerate in case of MPEG-2 repeat
 * frame mode.
 * The logical file position is not changed by this function;
 * examined packets may be buffered for later processing.
 *
 * @param ic media file handle
 * @param options  If non-NULL, an ic.nb_streams long array of pointers to
 *                 dictionaries, where i-th member contains options for
 *                 codec corresponding to i-th stream.
 *                 On return each dictionary will be filled with options that were not found.
 * @return >=0 if OK, AVERROR_xxx on error
 *
 * @note this function isn't guaranteed to open all the codecs, so
 *       options being non-empty at return is a perfectly normal behavior.
 *
 * @todo Let the user decide somehow what information is needed so that
 *       we do not waste time getting stuff the user does not need.
 */
int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options);

/**
 * Find the programs which belong to a given stream.
 *
 * @param ic    media file handle
 * @param last  the last found program, the search will start after this
 *              program, or from the beginning if it is NULL
 * @param s     stream index
 * @return the next program which belongs to s, NULL if no program is found or
 *         the last program is not among the programs of ic.
 */
AVProgram *av_find_program_from_stream(AVFormatContext *ic, AVProgram *last, int s);

/**
 * Find the "best" stream in the file.
 * The best stream is determined according to various heuristics as the most
 * likely to be what the user expects.
 * If the decoder parameter is non-NULL, av_find_best_stream will find the
 * default decoder for the stream's codec; streams for which no decoder can
 * be found are ignored.
 *
 * @param ic                media file handle
 * @param type              stream type: video, audio, subtitles, etc.
 * @param wanted_stream_nb  user-requested stream number,
 *                          or -1 for automatic selection
 * @param related_stream    try to find a stream related (eg. in the same
 *                          program) to this one, or -1 if none
 * @param decoder_ret       if non-NULL, returns the decoder for the
 *                          selected stream
 * @param flags             flags; none are currently defined
 * @return  the non-negative stream number in case of success,
 *          AVERROR_STREAM_NOT_FOUND if no stream with the requested type
 *          could be found,
 *          AVERROR_DECODER_NOT_FOUND if streams were found but no decoder
 * @note  If av_find_best_stream returns successfully and decoder_ret is not
 *        NULL, then *decoder_ret is guaranteed to be set to a valid AVCodec.
 */
int av_find_best_stream(AVFormatContext *ic,
                        enum AVMediaType type,
                        int wanted_stream_nb,
                        int related_stream,
                        AVCodec **decoder_ret,
                        int flags);

#if FF_API_READ_PACKET
/**
 * @deprecated use AVFMT_FLAG_NOFILLIN | AVFMT_FLAG_NOPARSE to read raw
 * unprocessed packets
 *
 * Read a transport packet from a media file.
 *
 * This function is obsolete and should never be used.
 * Use av_read_frame() instead.
 *
 * @param s media file handle
 * @param pkt is filled
 * @return 0 if OK, AVERROR_xxx on error
 */
attribute_deprecated
int av_read_packet(AVFormatContext *s, AVPacket *pkt);
#endif

/**
 * Return the next frame of a stream.
 * This function returns what is stored in the file, and does not validate
 * that what is there are valid frames for the decoder. It will split what is
 * stored in the file into frames and return one for each call. It will not
 * omit invalid data between valid frames so as to give the decoder the maximum
 * information possible for decoding.
 *
 * If pkt->buf is NULL, then the packet is valid until the next
 * av_read_frame() or until avformat_close_input(). Otherwise the packet
 * is valid indefinitely. In both cases the packet must be freed with
 * av_free_packet when it is no longer needed. For video, the packet contains
 * exactly one frame. For audio, it contains an integer number of frames if each
 * frame has a known fixed size (e.g. PCM or ADPCM data). If the audio frames
 * have a variable size (e.g. MPEG audio), then it contains one frame.
 *
 * pkt->pts, pkt->dts and pkt->duration are always set to correct
 * values in AVStream.time_base units (and guessed if the format cannot
 * provide them). pkt->pts can be AV_NOPTS_VALUE if the video format
 * has B-frames, so it is better to rely on pkt->dts if you do not
 * decompress the payload.
 *
 * @return 0 if OK, < 0 on error or end of file
 */
int av_read_frame(AVFormatContext *s, AVPacket *pkt);

/**
 * Seek to the keyframe at timestamp.
 * 'timestamp' in 'stream_index'.
 * @param stream_index If stream_index is (-1), a default
 * stream is selected, and timestamp is automatically converted
 * from AV_TIME_BASE units to the stream specific time_base.
 * @param timestamp Timestamp in AVStream.time_base units
 *        or, if no stream is specified, in AV_TIME_BASE units.
 * @param flags flags which select direction and seeking mode
 * @return >= 0 on success
 */
int av_seek_frame(AVFormatContext *s, int stream_index, int64_t timestamp,
                  int flags);

/**
 * Seek to timestamp ts.
 * Seeking will be done so that the point from which all active streams
 * can be presented successfully will be closest to ts and within min/max_ts.
 * Active streams are all streams that have AVStream.discard < AVDISCARD_ALL.
 *
 * If flags contain AVSEEK_FLAG_BYTE, then all timestamps are in bytes and
 * are the file position (this may not be supported by all demuxers).
 * If flags contain AVSEEK_FLAG_FRAME, then all timestamps are in frames
 * in the stream with stream_index (this may not be supported by all demuxers).
 * Otherwise all timestamps are in units of the stream selected by stream_index
 * or if stream_index is -1, in AV_TIME_BASE units.
 * If flags contain AVSEEK_FLAG_ANY, then non-keyframes are treated as
 * keyframes (this may not be supported by all demuxers).
 * If flags contain AVSEEK_FLAG_BACKWARD, it is ignored.
 *
 * @param stream_index index of the stream which is used as time base reference
 * @param min_ts smallest acceptable timestamp
 * @param ts target timestamp
 * @param max_ts largest acceptable timestamp
 * @param flags flags
 * @return >=0 on success, error code otherwise
 *
 * @note This is part of the new seek API which is still under construction.
 *       Thus do not use this yet. It may change at any time, do not expect
 *       ABI compatibility yet!
 */
int avformat_seek_file(AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags);

/**
 * Start playing a network-based stream (e.g. RTSP stream) at the
 * current position.
 */
int av_read_play(AVFormatContext *s);

/**
 * Pause a network-based stream (e.g. RTSP stream).
 *
 * Use av_read_play() to resume it.
 */
int av_read_pause(AVFormatContext *s);

#if FF_API_CLOSE_INPUT_FILE
/**
 * @deprecated use avformat_close_input()
 * Close a media file (but not its codecs).
 *
 * @param s media file handle
 */
attribute_deprecated
void av_close_input_file(AVFormatContext *s);
#endif

/**
 * Close an opened input AVFormatContext. Free it and all its contents
 * and set *s to NULL.
 */
void avformat_close_input(AVFormatContext **s);
/**
 * @}
 */

#if FF_API_NEW_STREAM
/**
 * Add a new stream to a media file.
 *
 * Can only be called in the read_header() function. If the flag
 * AVFMTCTX_NOHEADER is in the format context, then new streams
 * can be added in read_packet too.
 *
 * @param s media file handle
 * @param id file-format-dependent stream ID
 */
attribute_deprecated
AVStream *av_new_stream(AVFormatContext *s, int id);
#endif

#if FF_API_SET_PTS_INFO
/**
 * @deprecated this function is not supposed to be called outside of lavf
 */
attribute_deprecated
void av_set_pts_info(AVStream *s, int pts_wrap_bits,
                     unsigned int pts_num, unsigned int pts_den);
#endif

#define AVSEEK_FLAG_BACKWARD 1 ///< seek backward
#define AVSEEK_FLAG_BYTE     2 ///< seeking based on position in bytes
#define AVSEEK_FLAG_ANY      4 ///< seek to any frame, even non-keyframes
#define AVSEEK_FLAG_FRAME    8 ///< seeking based on frame number

/**
 * @addtogroup lavf_encoding
 * @{
 */
/**
 * Allocate the stream private data and write the stream header to
 * an output media file.
 *
 * @param s Media file handle, must be allocated with avformat_alloc_context().
 *          Its oformat field must be set to the desired output format;
 *          Its pb field must be set to an already opened AVIOContext.
 * @param options  An AVDictionary filled with AVFormatContext and muxer-private options.
 *                 On return this parameter will be destroyed and replaced with a dict containing
 *                 options that were not found. May be NULL.
 *
 * @return 0 on success, negative AVERROR on failure.
 *
 * @see av_opt_find, av_dict_set, avio_open, av_oformat_next.
 */
int avformat_write_header(AVFormatContext *s, AVDictionary **options);

/**
 * Write a packet to an output media file.
 *
 * This function passes the packet directly to the muxer, without any buffering
 * or reordering. The caller is responsible for correctly interleaving the
 * packets if the format requires it. Callers that want libavformat to handle
 * the interleaving should call av_interleaved_write_frame() instead of this
 * function.
 *
 * @param s media file handle
 * @param pkt @parblock
 *            The packet containing the data to be written. Note that unlike
 *            av_interleaved_write_frame(), this function does not take
 *            ownership of the packet passed to it (though some muxers may make
 *            an internal reference to the input packet).
 *
 *            This parameter can be NULL (at any time, not just at the end), in
 *            order to immediately flush data buffered within the muxer, for
 *            muxers that buffer up data internally before writing it to the
 *            output.
 *
 *            Packet's @ref AVPacket.stream_index "stream_index" field must be
 *            set to the index of the corresponding stream in @ref
 *            AVFormatContext.streams "s->streams". It is very strongly
 *            recommended that timing information (@ref AVPacket.pts "pts", @ref
 *            AVPacket.dts "dts", @ref AVPacket.duration "duration") is set to
 *            correct values.
 *            @endparblock
 * @return < 0 on error, = 0 if OK, 1 if flushed and there is no more data to flush
 *
 * @see av_interleaved_write_frame()
 */
int av_write_frame(AVFormatContext *s, AVPacket *pkt);

/**
 * Write a packet to an output media file ensuring correct interleaving.
 *
 * This function will buffer the packets internally as needed to make sure the
 * packets in the output file are properly interleaved in the order of
 * increasing dts. Callers doing their own interleaving should call
 * av_write_frame() instead of this function.
 *
 * @param s media file handle
 * @param pkt @parblock
 *            The packet containing the data to be written.
 *
 *            If the packet is reference-counted, this function will take
 *            ownership of this reference and unreference it later when it sees
 *            fit.
 *            The caller must not access the data through this reference after
 *            this function returns. If the packet is not reference-counted,
 *            libavformat will make a copy.
 *
 *            This parameter can be NULL (at any time, not just at the end), to
 *            flush the interleaving queues.
 *
 *            Packet's @ref AVPacket.stream_index "stream_index" field must be
 *            set to the index of the corresponding stream in @ref
 *            AVFormatContext.streams "s->streams". It is very strongly
 *            recommended that timing information (@ref AVPacket.pts "pts", @ref
 *            AVPacket.dts "dts", @ref AVPacket.duration "duration") is set to
 *            correct values.
 *            @endparblock
 *
 * @return 0 on success, a negative AVERROR on error. Libavformat will always
 *         take care of freeing the packet, even if this function fails.
 *
 * @see av_write_frame(), AVFormatContext.max_interleave_delta
 */
int av_interleaved_write_frame(AVFormatContext *s, AVPacket *pkt);

/**
 * Write a uncoded frame to an output media file.
 *
 * The frame must be correctly interleaved according to the container
 * specification; if not, then av_interleaved_write_frame() must be used.
 *
 * See av_interleaved_write_frame() for details.
 */
int av_write_uncoded_frame(AVFormatContext *s, int stream_index,
                           AVFrame *frame);

/**
 * Write a uncoded frame to an output media file.
 *
 * If the muxer supports it, this function allows to write an AVFrame
 * structure directly, without encoding it into a packet.
 * It is mostly useful for devices and similar special muxers that use raw
 * video or PCM data and will not serialize it into a byte stream.
 *
 * To test whether it is possible to use it with a given muxer and stream,
 * use av_write_uncoded_frame_query().
 *
 * The caller gives up ownership of the frame and must not access it
 * afterwards.
 *
 * @return  >=0 for success, a negative code on error
 */
int av_interleaved_write_uncoded_frame(AVFormatContext *s, int stream_index,
                                       AVFrame *frame);

/**
 * Test whether a muxer supports uncoded frame.
 *
 * @return  >=0 if an uncoded frame can be written to that muxer and stream,
 *          <0 if not
 */
int av_write_uncoded_frame_query(AVFormatContext *s, int stream_index);

/**
 * Write the stream trailer to an output media file and free the
 * file private data.
 *
 * May only be called after a successful call to avformat_write_header.
 *
 * @param s media file handle
 * @return 0 if OK, AVERROR_xxx on error
 */
int av_write_trailer(AVFormatContext *s);

/**
 * Return the output format in the list of registered output formats
 * which best matches the provided parameters, or return NULL if
 * there is no match.
 *
 * @param short_name if non-NULL checks if short_name matches with the
 * names of the registered formats
 * @param filename if non-NULL checks if filename terminates with the
 * extensions of the registered formats
 * @param mime_type if non-NULL checks if mime_type matches with the
 * MIME type of the registered formats
 */
AVOutputFormat *av_guess_format(const char *short_name,
                                const char *filename,
                                const char *mime_type);

/**
 * Guess the codec ID based upon muxer and filename.
 */
enum AVCodecID av_guess_codec(AVOutputFormat *fmt, const char *short_name,
                            const char *filename, const char *mime_type,
                            enum AVMediaType type);

/**
 * Get timing information for the data currently output.
 * The exact meaning of "currently output" depends on the format.
 * It is mostly relevant for devices that have an internal buffer and/or
 * work in real time.
 * @param s          media file handle
 * @param stream     stream in the media file
 * @param[out] dts   DTS of the last packet output for the stream, in stream
 *                   time_base units
 * @param[out] wall  absolute time when that packet whas output,
 *                   in microsecond
 * @return  0 if OK, AVERROR(ENOSYS) if the format does not support it
 * Note: some formats or devices may not allow to measure dts and wall
 * atomically.
 */
int av_get_output_timestamp(struct AVFormatContext *s, int stream,
                            int64_t *dts, int64_t *wall);


/**
 * @}
 */


/**
 * @defgroup lavf_misc Utility functions
 * @ingroup libavf
 * @{
 *
 * Miscellaneous utility functions related to both muxing and demuxing
 * (or neither).
 */

/**
 * Send a nice hexadecimal dump of a buffer to the specified file stream.
 *
 * @param f The file stream pointer where the dump should be sent to.
 * @param buf buffer
 * @param size buffer size
 *
 * @see av_hex_dump_log, av_pkt_dump2, av_pkt_dump_log2
 */
void av_hex_dump(FILE *f, const uint8_t *buf, int size);

/**
 * Send a nice hexadecimal dump of a buffer to the log.
 *
 * @param avcl A pointer to an arbitrary struct of which the first field is a
 * pointer to an AVClass struct.
 * @param level The importance level of the message, lower values signifying
 * higher importance.
 * @param buf buffer
 * @param size buffer size
 *
 * @see av_hex_dump, av_pkt_dump2, av_pkt_dump_log2
 */
void av_hex_dump_log(void *avcl, int level, const uint8_t *buf, int size);

/**
 * Send a nice dump of a packet to the specified file stream.
 *
 * @param f The file stream pointer where the dump should be sent to.
 * @param pkt packet to dump
 * @param dump_payload True if the payload must be displayed, too.
 * @param st AVStream that the packet belongs to
 */
void av_pkt_dump2(FILE *f, AVPacket *pkt, int dump_payload, AVStream *st);


/**
 * Send a nice dump of a packet to the log.
 *
 * @param avcl A pointer to an arbitrary struct of which the first field is a
 * pointer to an AVClass struct.
 * @param level The importance level of the message, lower values signifying
 * higher importance.
 * @param pkt packet to dump
 * @param dump_payload True if the payload must be displayed, too.
 * @param st AVStream that the packet belongs to
 */
void av_pkt_dump_log2(void *avcl, int level, AVPacket *pkt, int dump_payload,
                      AVStream *st);

/**
 * Get the AVCodecID for the given codec tag tag.
 * If no codec id is found returns AV_CODEC_ID_NONE.
 *
 * @param tags list of supported codec_id-codec_tag pairs, as stored
 * in AVInputFormat.codec_tag and AVOutputFormat.codec_tag
 */
enum AVCodecID av_codec_get_id(const struct AVCodecTag * const *tags, unsigned int tag);

/**
 * Get the codec tag for the given codec id id.
 * If no codec tag is found returns 0.
 *
 * @param tags list of supported codec_id-codec_tag pairs, as stored
 * in AVInputFormat.codec_tag and AVOutputFormat.codec_tag
 */
unsigned int av_codec_get_tag(const struct AVCodecTag * const *tags, enum AVCodecID id);

/**
 * Get the codec tag for the given codec id.
 *
 * @param tags list of supported codec_id - codec_tag pairs, as stored
 * in AVInputFormat.codec_tag and AVOutputFormat.codec_tag
 * @param id codec id that should be searched for in the list
 * @param tag A pointer to the found tag
 * @return 0 if id was not found in tags, > 0 if it was found
 */
int av_codec_get_tag2(const struct AVCodecTag * const *tags, enum AVCodecID id,
                      unsigned int *tag);

int av_find_default_stream_index(AVFormatContext *s);

/**
 * Get the index for a specific timestamp.
 * @param flags if AVSEEK_FLAG_BACKWARD then the returned index will correspond
 *                 to the timestamp which is <= the requested one, if backward
 *                 is 0, then it will be >=
 *              if AVSEEK_FLAG_ANY seek to any frame, only keyframes otherwise
 * @return < 0 if no such timestamp could be found
 */
int av_index_search_timestamp(AVStream *st, int64_t timestamp, int flags);

/**
 * Add an index entry into a sorted list. Update the entry if the list
 * already contains it.
 *
 * @param timestamp timestamp in the time base of the given stream
 */
int av_add_index_entry(AVStream *st, int64_t pos, int64_t timestamp,
                       int size, int distance, int flags);


/**
 * Split a URL string into components.
 *
 * The pointers to buffers for storing individual components may be null,
 * in order to ignore that component. Buffers for components not found are
 * set to empty strings. If the port is not found, it is set to a negative
 * value.
 *
 * @param proto the buffer for the protocol
 * @param proto_size the size of the proto buffer
 * @param authorization the buffer for the authorization
 * @param authorization_size the size of the authorization buffer
 * @param hostname the buffer for the host name
 * @param hostname_size the size of the hostname buffer
 * @param port_ptr a pointer to store the port number in
 * @param path the buffer for the path
 * @param path_size the size of the path buffer
 * @param url the URL to split
 */
void av_url_split(char *proto,         int proto_size,
                  char *authorization, int authorization_size,
                  char *hostname,      int hostname_size,
                  int *port_ptr,
                  char *path,          int path_size,
                  const char *url);


void av_dump_format(AVFormatContext *ic,
                    int index,
                    const char *url,
                    int is_output);

/**
 * Return in 'buf' the path with '%d' replaced by a number.
 *
 * Also handles the '%0nd' format where 'n' is the total number
 * of digits and '%%'.
 *
 * @param buf destination buffer
 * @param buf_size destination buffer size
 * @param path numbered sequence string
 * @param number frame number
 * @return 0 if OK, -1 on format error
 */
int av_get_frame_filename(char *buf, int buf_size,
                          const char *path, int number);

/**
 * Check whether filename actually is a numbered sequence generator.
 *
 * @param filename possible numbered sequence string
 * @return 1 if a valid numbered sequence string, 0 otherwise
 */
int av_filename_number_test(const char *filename);

/**
 * Generate an SDP for an RTP session.
 *
 * Note, this overwrites the id values of AVStreams in the muxer contexts
 * for getting unique dynamic payload types.
 *
 * @param ac array of AVFormatContexts describing the RTP streams. If the
 *           array is composed by only one context, such context can contain
 *           multiple AVStreams (one AVStream per RTP stream). Otherwise,
 *           all the contexts in the array (an AVCodecContext per RTP stream)
 *           must contain only one AVStream.
 * @param n_files number of AVCodecContexts contained in ac
 * @param buf buffer where the SDP will be stored (must be allocated by
 *            the caller)
 * @param size the size of the buffer
 * @return 0 if OK, AVERROR_xxx on error
 */
int av_sdp_create(AVFormatContext *ac[], int n_files, char *buf, int size);

/**
 * Return a positive value if the given filename has one of the given
 * extensions, 0 otherwise.
 *
 * @param extensions a comma-separated list of filename extensions
 */
int av_match_ext(const char *filename, const char *extensions);

/**
 * Test if the given container can store a codec.
 *
 * @param std_compliance standards compliance level, one of FF_COMPLIANCE_*
 *
 * @return 1 if codec with ID codec_id can be stored in ofmt, 0 if it cannot.
 *         A negative number if this information is not available.
 */
int avformat_query_codec(AVOutputFormat *ofmt, enum AVCodecID codec_id, int std_compliance);

/**
 * @defgroup riff_fourcc RIFF FourCCs
 * @{
 * Get the tables mapping RIFF FourCCs to libavcodec AVCodecIDs. The tables are
 * meant to be passed to av_codec_get_id()/av_codec_get_tag() as in the
 * following code:
 * @code
 * uint32_t tag = MKTAG('H', '2', '6', '4');
 * const struct AVCodecTag *table[] = { avformat_get_riff_video_tags(), 0 };
 * enum AVCodecID id = av_codec_get_id(table, tag);
 * @endcode
 */
/**
 * @return the table mapping RIFF FourCCs for video to libavcodec AVCodecID.
 */
const struct AVCodecTag *avformat_get_riff_video_tags(void);
/**
 * @return the table mapping RIFF FourCCs for audio to AVCodecID.
 */
const struct AVCodecTag *avformat_get_riff_audio_tags(void);
/**
 * @return the table mapping MOV FourCCs for video to libavcodec AVCodecID.
 */
const struct AVCodecTag *avformat_get_mov_video_tags(void);
/**
 * @return the table mapping MOV FourCCs for audio to AVCodecID.
 */
const struct AVCodecTag *avformat_get_mov_audio_tags(void);

/**
 * @}
 */

/**
 * Guess the sample aspect ratio of a frame, based on both the stream and the
 * frame aspect ratio.
 *
 * Since the frame aspect ratio is set by the codec but the stream aspect ratio
 * is set by the demuxer, these two may not be equal. This function tries to
 * return the value that you should use if you would like to display the frame.
 *
 * Basic logic is to use the stream aspect ratio if it is set to something sane
 * otherwise use the frame aspect ratio. This way a container setting, which is
 * usually easy to modify can override the coded value in the frames.
 *
 * @param format the format context which the stream is part of
 * @param stream the stream which the frame is part of
 * @param frame the frame with the aspect ratio to be determined
 * @return the guessed (valid) sample_aspect_ratio, 0/1 if no idea
 */
AVRational av_guess_sample_aspect_ratio(AVFormatContext *format, AVStream *stream, AVFrame *frame);

/**
 * Guess the frame rate, based on both the container and codec information.
 *
 * @param ctx the format context which the stream is part of
 * @param stream the stream which the frame is part of
 * @param frame the frame for which the frame rate should be determined, may be NULL
 * @return the guessed (valid) frame rate, 0/1 if no idea
 */
AVRational av_guess_frame_rate(AVFormatContext *ctx, AVStream *stream, AVFrame *frame);

/**
 * Check if the stream st contained in s is matched by the stream specifier
 * spec.
 *
 * See the "stream specifiers" chapter in the documentation for the syntax
 * of spec.
 *
 * @return  >0 if st is matched by spec;
 *          0  if st is not matched by spec;
 *          AVERROR code if spec is invalid
 *
 * @note  A stream specifier can match several streams in the format.
 */
int avformat_match_stream_specifier(AVFormatContext *s, AVStream *st,
                                    const char *spec);

int avformat_queue_attached_pictures(AVFormatContext *s);


/**
 * @}
 */

#endif /* AVFORMAT_AVFORMAT_H */