Muxing

Modules

 Utility functions
 Miscellaneous utility functions related to both muxing and demuxing (or neither).
 Demuxing
 Demuxers read a media file and split it into chunks of data (packets).

Data Structures

struct  AVOutputFormat

Typedefs

typedef struct AVOutputFormat AVOutputFormat

Functions

int avformat_write_header (AVFormatContext *s, AVDictionary **options)
 Allocate the stream private data and write the stream header to an output media file.
int av_write_frame (AVFormatContext *s, AVPacket *pkt)
 Write a packet to an output media file.
int av_interleaved_write_frame (AVFormatContext *s, AVPacket *pkt)
 Write a packet to an output media file ensuring correct interleaving.
int av_write_trailer (AVFormatContext *s)
 Write the stream trailer to an output media file and free the file private data.
AVOutputFormatav_guess_format (const char *short_name, const char *filename, const char *mime_type)
 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.
enum AVCodecID av_guess_codec (AVOutputFormat *fmt, const char *short_name, const char *filename, const char *mime_type, enum AVMediaType type)
 Guess the codec ID based upon muxer and filename.

Detailed Description

Allocate and read the payload of a packet and initialize its fields with default values.

Parameters
pktpacket
sizedesired payload size
Returns
>0 (read size) if OK, AVERROR_xxx otherwise

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.

Parameters
pktpacket
sizeamount of data to read
Returns
>0 (read size) if OK, AVERROR_xxx otherwise, previous data will not be lost even if an error occurs.

The exact value of the fractional number is: 'val + num / den'. num is assumed to be 0 <= num < den.

This structure contains the data a format has to probe a file.

< Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.

< Size of buf except extra allocated bytes

Demuxer will use avio_open, no opened file should be provided by the caller.

Typedef Documentation

Function Documentation

enum AVCodecID av_guess_codec ( AVOutputFormat fmt,
const char *  short_name,
const char *  filename,
const char *  mime_type,
enum AVMediaType  type 
)

Guess the codec ID based upon muxer and filename.

Definition at line 186 of file utils.c.

Referenced by choose_encoder().

AVOutputFormat* av_guess_format ( const char *  short_name,
const char *  filename,
const char *  mime_type 
)

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.

Parameters
short_nameif non-NULL checks if short_name matches with the names of the registered formats
filenameif non-NULL checks if filename terminates with the extensions of the registered formats
mime_typeif non-NULL checks if mime_type matches with the MIME type of the registered formats
Examples:
libavformat/output-example.c.

Definition at line 151 of file utils.c.

Referenced by av_guess_format(), avserver_guess_format(), ff_rtp_chain_mux_open(), hls_write_header(), ism_write_header(), main(), mpegts_write_header(), open_output_file(), parse_ffconfig(), rtp_new_av_stream(), seg_write_header(), and show_help_muxer().

int av_interleaved_write_frame ( AVFormatContext s,
AVPacket pkt 
)

Write a packet to an output media file ensuring correct interleaving.

The packet must contain one audio or video frame. If the packets are already correctly interleaved, the application should call av_write_frame() instead as it is slightly faster. It is also important to keep in mind that completely non-interleaved input will need huge amounts of memory to interleave with this, so it is preferable to interleave at the demuxer level.

Parameters
smedia file handle
pktThe packet containing the data to be written. Libavformat takes ownership of the data and will free it when it sees fit using the packet's destruct field. The caller must not access the data after this function returns, as it may already be freed. This can be NULL (at any time, not just at the end), to flush the interleaving queues. Packet's stream_index field must be set to the index of the corresponding stream in s.streams. It is very strongly recommended that timing information (pts, dts duration) is set to correct values.
Returns
0 on success, a negative AVERROR on error.
Examples:
libavformat/output-example.c.

Definition at line 524 of file mux.c.

Referenced by write_audio_frame(), write_frame(), and write_video_frame().

int av_write_frame ( AVFormatContext s,
AVPacket pkt 
)

Write a packet to an output media file.

The packet shall contain one audio or video frame. The packet must be correctly interleaved according to the container specification, if not then av_interleaved_write_frame must be used.

Parameters
smedia file handle
pktThe packet, which contains the stream_index, buf/buf_size, dts/pts, ... This 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.
Returns
< 0 on error, = 0 if OK, 1 if flushed and there is no more data to flush

Definition at line 394 of file mux.c.

Referenced by ff_write_chained(), hls_write_packet(), http_prepare_data(), ism_flush(), mpegts_write_packet_internal(), and segment_end().

int av_write_trailer ( AVFormatContext s)

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.

Parameters
smedia file handle
Returns
0 if OK, AVERROR_xxx on error
Examples:
libavformat/output-example.c.

Definition at line 565 of file mux.c.

Referenced by close_connection(), ff_mov_close_hinting(), ff_rtsp_undo_setup(), hls_write_trailer(), http_prepare_data(), ism_free(), main(), sap_write_close(), seg_write_trailer(), segment_end(), and transcode().

int avformat_write_header ( AVFormatContext s,
AVDictionary **  options 
)

Allocate the stream private data and write the stream header to an output media file.

Parameters
sMedia 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 openened AVIOContext.
optionsAn 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.
Returns
0 on success, negative AVERROR on failure.
See Also
av_opt_find, av_dict_set, avio_open, av_oformat_next.
Examples:
libavformat/output-example.c.

Definition at line 295 of file mux.c.

Referenced by build_feed_streams(), ff_rtp_chain_mux_open(), hls_write_header(), http_prepare_data(), ism_write_header(), main(), mpegts_write_header(), rtp_new_av_stream(), seg_write_header(), segment_start(), and transcode_init().