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@chapter Format Options

@c man begin FORMAT OPTIONS

The libavformat library provides some generic global options, which

can be set on all the muxers and demuxers. In addition each muxer or

demuxer may support so-called private options, which are specific for

that component.

Options may be set by specifying -@var{option} @var{value} in the

FFmpeg tools, or by setting the value explicitly in the

@code{AVFormatContext} options or using the @file{libavutil/opt.h} API

for programmatic use.

The list of supported options follows:

@table @option

@item avioflags @var{flags} (@emph{input/output})

Possible values:

@table @samp

@item direct

Reduce buffering.

@end table

@item probesize @var{integer} (@emph{input})

Set probing size in bytes, i.e. the size of the data to analyze to get

stream information. A higher value will allow to detect more

information in case it is dispersed into the stream, but will increase

latency. Must be an integer not lesser than 32. It is 5000000 by default.

@item packetsize @var{integer} (@emph{output})

Set packet size.

@item fflags @var{flags} (@emph{input/output})

Set format flags.

Possible values:

@table @samp

@item ignidx

Ignore index.

@item genpts

Generate PTS.

@item nofillin

Do not fill in missing values that can be exactly calculated.

@item noparse

Disable AVParsers, this needs @code{+nofillin} too.

@item igndts

Ignore DTS.

@item discardcorrupt

Discard corrupted frames.

@item sortdts

Try to interleave output packets by DTS.

@item keepside

Do not merge side data.

@item latm

Enable RTP MP4A-LATM payload.

@item nobuffer

Reduce the latency introduced by optional buffering

@end table

@item seek2any @var{integer} (@emph{input})

Allow seeking to non-keyframes on demuxer level when supported if set to 1.

Default is 0.

@item analyzeduration @var{integer} (@emph{input})

Specify how many microseconds are analyzed to probe the input. A

higher value will allow to detect more accurate information, but will

increase latency. It defaults to 5,000,000 microseconds = 5 seconds.

@item cryptokey @var{hexadecimal string} (@emph{input})

Set decryption key.

@item indexmem @var{integer} (@emph{input})

Set max memory used for timestamp index (per stream).

@item rtbufsize @var{integer} (@emph{input})

Set max memory used for buffering real-time frames.

@item fdebug @var{flags} (@emph{input/output})

Print specific debug info.

Possible values:

@table @samp

@item ts

@end table

@item max_delay @var{integer} (@emph{input/output})

Set maximum muxing or demuxing delay in microseconds.

@item fpsprobesize @var{integer} (@emph{input})

Set number of frames used to probe fps.

@item audio_preload @var{integer} (@emph{output})

Set microseconds by which audio packets should be interleaved earlier.

@item chunk_duration @var{integer} (@emph{output})

Set microseconds for each chunk.

@item chunk_size @var{integer} (@emph{output})

Set size in bytes for each chunk.

@item err_detect, f_err_detect @var{flags} (@emph{input})

Set error detection flags. @code{f_err_detect} is deprecated and

should be used only via the @command{ffmpeg} tool.

Possible values:

@table @samp

@item crccheck

Verify embedded CRCs.

@item bitstream

Detect bitstream specification deviations.

@item buffer

Detect improper bitstream length.

@item explode

Abort decoding on minor error detection.

@item careful

Consider things that violate the spec and have not been seen in the

wild as errors.

@item compliant

Consider all spec non compliancies as errors.

@item aggressive

Consider things that a sane encoder should not do as an error.

@end table

@item use_wallclock_as_timestamps @var{integer} (@emph{input})

Use wallclock as timestamps.

@item avoid_negative_ts @var{integer} (@emph{output})

Shift timestamps to make them non-negative. A value of 1 enables shifting,

a value of 0 disables it, the default value of -1 enables shifting

when required by the target format.

When shifting is enabled, all output timestamps are shifted by the

same amount. Audio, video, and subtitles desynching and relative

timestamp differences are preserved compared to how they would have

been without shifting.

Also note that this affects only leading negative timestamps, and not

non-monotonic negative timestamps.

@item skip_initial_bytes @var{integer} (@emph{input})

Set number of bytes to skip before reading header and frames if set to 1.

Default is 0.

@item correct_ts_overflow @var{integer} (@emph{input})

Correct single timestamp overflows if set to 1. Default is 1.

@item flush_packets @var{integer} (@emph{output})

Flush the underlying I/O stream after each packet. Default 1 enables it, and

has the effect of reducing the latency; 0 disables it and may slightly

increase performance in some cases.

@end table

@c man end FORMAT OPTIONS

@anchor{Format stream specifiers}

@section Format stream specifiers

Format stream specifiers allow selection of one or more streams that

match specific properties.

Possible forms of stream specifiers are:

@table @option

@item @var{stream_index}

Matches the stream with this index.

@item @var{stream_type}[:@var{stream_index}]

@var{stream_type} is one of following: 'v' for video, 'a' for audio,

's' for subtitle, 'd' for data, and 't' for attachments. If

@var{stream_index} is given, then it matches the stream number

@var{stream_index} of this type. Otherwise, it matches all streams of

this type.

@item p:@var{program_id}[:@var{stream_index}]

If @var{stream_index} is given, then it matches the stream with number

@var{stream_index} in the program with the id

@var{program_id}. Otherwise, it matches all streams in the program.

@item #@var{stream_id}

Matches the stream by a format-specific ID.

@end table

The exact semantics of stream specifiers is defined by the

@code{avformat_match_stream_specifier()} function declared in the

@file{libavformat/avformat.h} header.

@include demuxers.texi

@include muxers.texi

@include metadata.texi