AVFormatContext

AVFormatContext是描述媒体文件或者媒体流的构成和基本信息

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;//用于记录和@ref avoptions的类。由avformat_alloc_context（）设置/*** The input container format.//输入容器格式。** Demuxing only, set by avformat_open_input().*/struct AVInputFormat *iformat;/*** The output container format.//输出容器格式** Muxing only, must be set by the caller before avformat_write_header().*/struct AVOutputFormat *oformat;/*** Format private data. This is an AVOptions-enabled struct //格式化私有数据。这是一个支持AVOptions的结构* 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;//输入数据的缓存/* stream info */   //流信息/*** Flags signalling stream properties. A combination of AVFMTCTX_*.* Set by libavformat.*/int ctx_flags; //标记信令流属性。AVFMTCTX的组合。/*** Number of elements in AVFormatContext.streams.** Set by avformat_new_stream(), must not be modified by any other code.*/unsigned int nb_streams;//流个数/*** 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;//文件中所有流的列表。使用创建新流#if FF_API_FORMAT_FILENAME/*** input or output filename  //输入或输出文件名** - demuxing: set by avformat_open_input()* - muxing: may be set by the caller before avformat_write_header()** @deprecated Use url instead.*/attribute_deprecatedchar filename[1024];//文件名
#endif/*** input or output URL. Unlike the old filename field, this field has no* length restriction.** - demuxing: set by avformat_open_input(), initialized to an empty*             string if url parameter was NULL in avformat_open_input().* - muxing: may be set by the caller before calling avformat_write_header()*           (or avformat_init_output() if that is called first) to a string*           which is freeable by av_free(). Set to an empty string if it*           was NULL in avformat_init_output().** Freed by libavformat in avformat_free_context().*/char *url;//输入或输出URL。/*** 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;//第一个帧的开始时间/*** 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;//持续时长/*** 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.*/int64_t bit_rate;//比特率unsigned int packet_size;//包大小int max_delay;//最大延迟/*** 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
#if FF_API_LAVF_MP4A_LATM
#define AVFMT_FLAG_MP4A_LATM    0x8000 ///< Deprecated, does nothing.
#endif
#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)
#if FF_API_LAVF_KEEPSIDE_FLAG
#define AVFMT_FLAG_KEEP_SIDE_DATA 0x40000 ///< Deprecated, does nothing.
#endif
#define AVFMT_FLAG_FAST_SEEK   0x80000 ///< Enable fast, but inaccurate seeks for some formats
#define AVFMT_FLAG_SHORTEST   0x100000 ///< Stop muxing when the shortest stream stops.
#define AVFMT_FLAG_AUTO_BSF   0x200000 ///< Add bitstream filters as requested by the muxer/*** Maximum size of the data read from input for determining* the input container format.* Demuxing only, set by the caller before avformat_open_input().*/int64_t 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().* Can be set to 0 to let avformat choose using a heuristic.*/int64_t 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* - 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* - 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* - 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*/int use_wallclock_as_timestamps;/*** avio flags, used to force AVIO_FLAG_DIRECT.* - encoding: unused* - decoding: Set by user*/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*/enum AVDurationEstimationMethod duration_estimation_method;/*** Skip initial bytes when opening stream* - encoding: unused* - decoding: Set by user*/int64_t skip_initial_bytes;/*** Correct single timestamp overflows* - encoding: unused* - decoding: Set by user*/unsigned int correct_ts_overflow;/*** Force seeking to any (also non key) frames.* - encoding: unused* - decoding: Set by user*/int seek2any;/*** Flush the I/O context after each packet.* - encoding: Set by user* - 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*/int probe_score;/*** number of bytes to read maximally to identify format.* - encoding: unused* - decoding: set by user*/int format_probesize;/*** ',' separated list of allowed decoders.* If NULL then all are allowed* - encoding: unused* - decoding: set by user*/char *codec_whitelist;/*** ',' separated list of allowed demuxers.* If NULL then all are allowed* - encoding: unused* - decoding: set by user*/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*/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*/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*/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*/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.*/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*/int64_t output_ts_offset;/*** dump format separator.* can be ", " or "\n      " or anything else* - 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;#if FF_API_OLD_OPEN_CALLBACKS/*** Called to open further IO contexts when needed for demuxing.** This can be set by the user application to perform security checks on* the URLs before opening them.* The function should behave like avio_open2(), AVFormatContext is provided* as contextual information and to reach AVFormatContext.opaque.** If NULL then some simple checks are used together with avio_open2().** Must not be accessed directly from outside avformat.* @See av_format_set_open_cb()** Demuxing: Set by user.** @deprecated Use io_open and io_close.*/attribute_deprecatedint (*open_cb)(struct AVFormatContext *s, AVIOContext **p, const char *url, int flags, const AVIOInterruptCB *int_cb, AVDictionary **options);
#endif/*** ',' separated list of allowed protocols.* - encoding: unused* - decoding: set by user*/char *protocol_whitelist;/*** A callback for opening new IO streams.** Whenever a muxer or a demuxer needs to open an IO stream (typically from* avformat_open_input() for demuxers, but for certain formats can happen at* other times as well), it will call this callback to obtain an IO context.** @param s the format context* @param pb on success, the newly opened IO context should be returned here* @param url the url to open* @param flags a combination of AVIO_FLAG_** @param options a dictionary of additional options, with the same*                semantics as in avio_open2()* @return 0 on success, a negative AVERROR code on failure** @note Certain muxers and demuxers do nesting, i.e. they open one or more* additional internal format contexts. Thus the AVFormatContext pointer* passed to this callback may be different from the one facing the caller.* It will, however, have the same 'opaque' field.*/int (*io_open)(struct AVFormatContext *s, AVIOContext **pb, const char *url,int flags, AVDictionary **options);/*** A callback for closing the streams opened with AVFormatContext.io_open().*/void (*io_close)(struct AVFormatContext *s, AVIOContext *pb);/*** ',' separated list of disallowed protocols.* - encoding: unused* - decoding: set by user*/char *protocol_blacklist;/*** The maximum number of streams.* - encoding: unused* - decoding: set by user*/int max_streams;/*** Skip duration calcuation in estimate_timings_from_pts.* - encoding: unused* - decoding: set by user*/int skip_estimate_duration_from_pts;
}

AVFormatContext相关推荐

【Android FFMPEG 开发】FFMPEG 获取 AVStream 音视频流 ( AVFormatContext 结构体 | 获取音视频流信息 | 获取音视频流个数 | 获取音视频流 )
文章目录博客简介 . FFMPEG 音视频流获取流程 I . FFMPEG 获取音视频流信息 ( AVFormatContext 结构体 ) II . FFMPEG 获取音视频流数量 III ...
FFMPEG结构体分析之AVFormatContext
它是FFMPEG解封装(flv,mp4,rmvb,avi)功能的结构体. 接口定义文件路径ffmpeg\libavformat\avformat.h, 看完该结构体的定义,就一句感慨,尼玛好长 /** ...
解封装(三):AVFormatContext分析
AVFormatContext是一个结构体,我们在IDE中对其转到定义之后,会发现有很多它的成员. 1.AVIOContext *pb:指的是我们自己定义一个读写格式. 2.char filename ...
FFmpeg源代码简单分析：常见结构体的初始化和销毁（AVFormatContext，AVFrame等）
===================================================== FFmpeg的库函数源代码分析文章列表: [架构图] FFmpeg源代码结构图 - 解码 F ...
FFMPEG结构体分析：AVFormatContext
注:写了一系列的结构体的分析的文章,在这里列一个列表: FFMPEG结构体分析:AVFrame FFMPEG结构体分析:AVFormatContext FFMPEG结构体分析:AVCodecConte ...
AVFormatContext、AV_read_frame、av_seek_frame
一. AVFormatContext 结构体描述了一个媒体文件或媒体流的构成和基本信息 int avformat_open_input(AVFormatContext **ps,const char ...
FFMPEG学习(4)-使用ffmpeg读取基本音视频文件信息，熟释AVFormatContext结构
前段时间把环境整了下,闲时学习下ffmpeg. 最近在看雷神的创作,边看,边学,感谢雷神! 头文件: // // ffmpeg_read_av_info.hpp // ffmpegDemo // // ...
【FFmpeg】结构体详解（一）：AVCodec、AVCodecContext、AVCodecParserContext、AVFrame、AVFormatContext 、AVIOContext
FFmpeg结构体详解一.FFmpeg中最关键的结构体之间的关系 1.解协议(http,rtsp,rtmp,mms) 2.解封装(flv,avi,rmvb,mp4) 3.解码(h264,mpeg2, ...
ffmpeg architecture（下）
ffmpeg architecture(下) 第3章-转码 TLDR:给我看代码和执行. $ make run_transcoding 我们将跳过一些细节,但是请放心:源代码可在github上找到. ...

AVFormatContext

AVFormatContext相关推荐

最新文章

热门文章