ffmpeg接收网络流AVFormatContext设置

   在使用ffmpeg接收网络ts流时，如不对AVFormatContext作设置，则在执行avformat_find_stream_info时会出现等待时间过长的情况。

   需设置的两个参数为probesize，max_analyze_duration，分别代表为确定输入格式而从输入读取的最大数据大小以及从输入avformat_find_stream_info()中读取数据的最大持续时间，将其设置足够大即可。

    /**     * @deprecated deprecated in favor of probesize2     */    unsigned int probesize;    /**     * @deprecated deprecated in favor of max_analyze_duration2     */    attribute_deprecated    int max_analyze_duration;    /**     * 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()     * via AVOptions (NO direct access).     * Can be set to 0 to let avformat choose using a heuristic.     */    int64_t max_analyze_duration2;    /**     * Maximum size of the data read from input for determining     * the input container format.     * Demuxing only, set by the caller before avformat_open_input()     * via AVOptions (NO direct access).     */    int64_t probesize2;

    AVFormatContext结构如下：

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 */    /**     * Flags signalling stream properties. A combination of AVFMTCTX_*.     * Set by libavformat.     */    int ctx_flags;    /**     * 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;    /**     * Flags modifying the (de)muxer behaviour. A combination of AVFMT_FLAG_*.     * Set by the user before avformat_open_input() / avformat_write_header().     */    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./** * When muxing, try to avoid writing any random/volatile data to the output. * This includes any random IDs, real-time timestamps/dates, muxer version, etc. * * This flag is mainly intended for testing. */#define AVFMT_FLAG_BITEXACT         0x0400#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.    /**     * @deprecated deprecated in favor of probesize2     */    unsigned int probesize;    /**     * @deprecated deprecated in favor of max_analyze_duration2     */    attribute_deprecated    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: Set by the caller before avformat_write_header(). If set to     *           either 0 or AV_NOPTS_VALUE, then the current wall-time will     *           be used.     * - demuxing: Set by libavformat. AV_NOPTS_VALUE if unknown. Note that     *             the value may become known after some number of frames     *             have been received.     */    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;    /**     * Allow non-standard and experimental extension     * @see AVCodecContext.strict_std_compliance     */    int strict_std_compliance;    /**     * Flags for the user to detect events happening on the file. Flags must     * be cleared by the user once the event has been handled.     * A combination of AVFMT_EVENT_FLAG_*.     */    int event_flags;#define AVFMT_EVENT_FLAG_METADATA_UPDATED 0x0001 ///< The call resulted in updated metadata.    /**     * Maximum number of packets to read while waiting for the first timestamp.     * Decoding only.     */    int max_ts_probe;    /**     * Avoid negative timestamps during muxing.     * Any value of the AVFMT_AVOID_NEG_TS_* constants.     * Note, this only works when using av_interleaved_write_frame. (interleave_packet_per_dts is in use)     * - muxing: Set by user     * - demuxing: unused     */    int avoid_negative_ts;#define AVFMT_AVOID_NEG_TS_AUTO             -1 ///< Enabled when required by target format#define AVFMT_AVOID_NEG_TS_MAKE_NON_NEGATIVE 1 ///< Shift timestamps so they are non negative#define AVFMT_AVOID_NEG_TS_MAKE_ZERO         2 ///< Shift timestamps so that they start at 0    /**     * 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;    /**     * 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)     */    int64_t 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;    /**     * number of bytes to read maximally to identify format.     * - encoding: unused     * - decoding: set by user through AVOPtions (NO direct access)     */    int format_probesize;    /**     * ',' separated list of allowed decoders.     * If NULL then all are allowed     * - encoding: unused     * - decoding: set by user through AVOptions (NO direct access)     */    char *codec_whitelist;    /**     * ',' separated list of allowed demuxers.     * If NULL then all are allowed     * - encoding: unused     * - decoding: set by user through AVOptions (NO direct access)     */    char *format_whitelist;    /**     * 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;    /**     * Forced data 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_data_codec (NO direct access).     */    AVCodec *data_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;    /**     * 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()     * via AVOptions (NO direct access).     * Can be set to 0 to let avformat choose using a heuristic.     */    int64_t max_analyze_duration2;    /**     * Maximum size of the data read from input for determining     * the input container format.     * Demuxing only, set by the caller before avformat_open_input()     * via AVOptions (NO direct access).     */    int64_t probesize2;    /**     * dump format separator.     * can be ", " or "\n      " or anything else     * Code outside libavformat should access this field using AVOptions     * (NO direct access).     * - muxing: Set by user.     * - demuxing: Set by user.     */    uint8_t *dump_separator;    /**     * Forced Data codec_id.     * Demuxing: Set by user.     */    enum AVCodecID data_codec_id;} AVFormatContext;