ed9363052f
Yet another probesize used to get the durations when estimate_timings_from_pts is required. It is aimed at users interested in better durations probing for itself, or because using avformat_find_stream_info indirectly and requiring exact values: for concatdec for example, especially if streamcopying above it. The current code is a performance trade-off that can fail to get video stream durations in a scenario with high bitrates and buffering for files ending cleanly (as opposed to live captures): the physical gap between the last video packet and the last audio packet is very high in such a case. Default behaviour is unchanged: 250k up to 250k << 6 (step by step). Setting this new option has two effects: - override the maximum probesize (currently 250k << 6) - reduce the number of steps to 1 instead of 6, this is to avoid detecting the audio "too early" and failing to reach a video packet. Even if a single audio stream duration is found but not the other audio/video stream durations, there will be a retry, so at the end the full user-overriden probesize will be used as expected by the user. Signed-off-by: Nicolas Gaullier <nicolas.gaullier@cji.paris>
291 lines
10 KiB
Plaintext
291 lines
10 KiB
Plaintext
@chapter Format Options
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@c man begin FORMAT OPTIONS
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The libavformat library provides some generic global options, which
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can be set on all the muxers and demuxers. In addition each muxer or
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demuxer may support so-called private options, which are specific for
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that component.
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Options may be set by specifying -@var{option} @var{value} in the
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FFmpeg tools, or by setting the value explicitly in the
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@code{AVFormatContext} options or using the @file{libavutil/opt.h} API
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for programmatic use.
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The list of supported options follows:
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@table @option
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@item avioflags @var{flags} (@emph{input/output})
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Possible values:
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@table @samp
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@item direct
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Reduce buffering.
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@end table
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@item probesize @var{integer} (@emph{input})
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Set probing size in bytes, i.e. the size of the data to analyze to get
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stream information. A higher value will enable detecting more
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information in case it is dispersed into the stream, but will increase
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latency. Must be an integer not lesser than 32. It is 5000000 by default.
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@item max_probe_packets @var{integer} (@emph{input})
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Set the maximum number of buffered packets when probing a codec.
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Default is 2500 packets.
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@item packetsize @var{integer} (@emph{output})
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Set packet size.
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@item fflags @var{flags}
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Set format flags. Some are implemented for a limited number of formats.
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Possible values for input files:
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@table @samp
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@item discardcorrupt
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Discard corrupted packets.
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@item fastseek
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Enable fast, but inaccurate seeks for some formats.
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@item genpts
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Generate missing PTS if DTS is present.
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@item igndts
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Ignore DTS if PTS is also set. In case the PTS is set, the DTS value
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is set to NOPTS. This is ignored when the @code{nofillin} flag is set.
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@item ignidx
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Ignore index.
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@item nobuffer
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Reduce the latency introduced by buffering during initial input streams analysis.
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@item nofillin
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Do not fill in missing values in packet fields that can be exactly calculated.
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@item noparse
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Disable AVParsers, this needs @code{+nofillin} too.
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@item sortdts
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Try to interleave output packets by DTS. At present, available only for AVIs with an index.
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@end table
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Possible values for output files:
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@table @samp
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@item autobsf
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Automatically apply bitstream filters as required by the output format. Enabled by default.
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@item bitexact
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Only write platform-, build- and time-independent data.
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This ensures that file and data checksums are reproducible and match between
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platforms. Its primary use is for regression testing.
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@item flush_packets
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Write out packets immediately.
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@item shortest
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Stop muxing at the end of the shortest stream.
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It may be needed to increase max_interleave_delta to avoid flushing the longer
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streams before EOF.
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@end table
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@item seek2any @var{integer} (@emph{input})
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Allow seeking to non-keyframes on demuxer level when supported if set to 1.
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Default is 0.
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@item analyzeduration @var{integer} (@emph{input})
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Specify how many microseconds are analyzed to probe the input. A
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higher value will enable detecting more accurate information, but will
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increase latency. It defaults to 5,000,000 microseconds = 5 seconds.
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@item cryptokey @var{hexadecimal string} (@emph{input})
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Set decryption key.
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@item indexmem @var{integer} (@emph{input})
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Set max memory used for timestamp index (per stream).
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@item rtbufsize @var{integer} (@emph{input})
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Set max memory used for buffering real-time frames.
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@item fdebug @var{flags} (@emph{input/output})
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Print specific debug info.
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Possible values:
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@table @samp
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@item ts
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@end table
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@item max_delay @var{integer} (@emph{input/output})
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Set maximum muxing or demuxing delay in microseconds.
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@item fpsprobesize @var{integer} (@emph{input})
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Set number of frames used to probe fps.
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@item audio_preload @var{integer} (@emph{output})
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Set microseconds by which audio packets should be interleaved earlier.
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@item chunk_duration @var{integer} (@emph{output})
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Set microseconds for each chunk.
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@item chunk_size @var{integer} (@emph{output})
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Set size in bytes for each chunk.
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@item err_detect, f_err_detect @var{flags} (@emph{input})
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Set error detection flags. @code{f_err_detect} is deprecated and
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should be used only via the @command{ffmpeg} tool.
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Possible values:
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@table @samp
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@item crccheck
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Verify embedded CRCs.
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@item bitstream
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Detect bitstream specification deviations.
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@item buffer
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Detect improper bitstream length.
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@item explode
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Abort decoding on minor error detection.
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@item careful
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Consider things that violate the spec and have not been seen in the
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wild as errors.
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@item compliant
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Consider all spec non compliancies as errors.
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@item aggressive
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Consider things that a sane encoder should not do as an error.
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@end table
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@item max_interleave_delta @var{integer} (@emph{output})
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Set maximum buffering duration for interleaving. The duration is
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expressed in microseconds, and defaults to 10000000 (10 seconds).
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To ensure all the streams are interleaved correctly, libavformat will
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wait until it has at least one packet for each stream before actually
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writing any packets to the output file. When some streams are
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"sparse" (i.e. there are large gaps between successive packets), this
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can result in excessive buffering.
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This field specifies the maximum difference between the timestamps of the
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first and the last packet in the muxing queue, above which libavformat
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will output a packet regardless of whether it has queued a packet for all
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the streams.
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If set to 0, libavformat will continue buffering packets until it has
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a packet for each stream, regardless of the maximum timestamp
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difference between the buffered packets.
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@item use_wallclock_as_timestamps @var{integer} (@emph{input})
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Use wallclock as timestamps if set to 1. Default is 0.
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@item avoid_negative_ts @var{integer} (@emph{output})
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Possible values:
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@table @samp
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@item make_non_negative
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Shift timestamps to make them non-negative.
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Also note that this affects only leading negative timestamps, and not
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non-monotonic negative timestamps.
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@item make_zero
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Shift timestamps so that the first timestamp is 0.
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@item auto (default)
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Enables shifting when required by the target format.
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@item disabled
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Disables shifting of timestamp.
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@end table
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When shifting is enabled, all output timestamps are shifted by the
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same amount. Audio, video, and subtitles desynching and relative
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timestamp differences are preserved compared to how they would have
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been without shifting.
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@item skip_initial_bytes @var{integer} (@emph{input})
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Set number of bytes to skip before reading header and frames if set to 1.
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Default is 0.
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@item correct_ts_overflow @var{integer} (@emph{input})
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Correct single timestamp overflows if set to 1. Default is 1.
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@item flush_packets @var{integer} (@emph{output})
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Flush the underlying I/O stream after each packet. Default is -1 (auto), which
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means that the underlying protocol will decide, 1 enables it, and has the
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effect of reducing the latency, 0 disables it and may increase IO throughput in
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some cases.
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@item output_ts_offset @var{offset} (@emph{output})
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Set the output time offset.
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@var{offset} must be a time duration specification,
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see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.
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The offset is added by the muxer to the output timestamps.
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Specifying a positive offset means that the corresponding streams are
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delayed bt the time duration specified in @var{offset}. Default value
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is @code{0} (meaning that no offset is applied).
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@item format_whitelist @var{list} (@emph{input})
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"," separated list of allowed demuxers. By default all are allowed.
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@item dump_separator @var{string} (@emph{input})
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Separator used to separate the fields printed on the command line about the
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Stream parameters.
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For example, to separate the fields with newlines and indentation:
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@example
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ffprobe -dump_separator "
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" -i ~/videos/matrixbench_mpeg2.mpg
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@end example
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@item max_streams @var{integer} (@emph{input})
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Specifies the maximum number of streams. This can be used to reject files that
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would require too many resources due to a large number of streams.
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@item skip_estimate_duration_from_pts @var{bool} (@emph{input})
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Skip estimation of input duration if it requires an additional probing for PTS at end of file.
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At present, applicable for MPEG-PS and MPEG-TS.
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@item duration_probesize @var{integer} (@emph{input})
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Set probing size, in bytes, for input duration estimation when it actually requires
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an additional probing for PTS at end of file (at present: MPEG-PS and MPEG-TS).
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It is aimed at users interested in better durations probing for itself, or indirectly
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because using the concat demuxer, for example.
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The typical use case is an MPEG-TS CBR with a high bitrate, high video buffering and
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ending cleaning with similar PTS for video and audio: in such a scenario, the large
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physical gap between the last video packet and the last audio packet makes it necessary
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to read many bytes in order to get the video stream duration.
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Another use case is where the default probing behaviour only reaches a single video frame which is
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not the last one of the stream due to frame reordering, so the duration is not accurate.
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Setting this option has a performance impact even for small files because the probing
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size is fixed.
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Default behaviour is a general purpose trade-off, largely adaptive, but the probing size
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will not be extended to get streams durations at all costs.
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Must be an integer not lesser than 1, or 0 for default behaviour.
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@item strict, f_strict @var{integer} (@emph{input/output})
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Specify how strictly to follow the standards. @code{f_strict} is deprecated and
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should be used only via the @command{ffmpeg} tool.
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Possible values:
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@table @samp
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@item very
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strictly conform to an older more strict version of the spec or reference software
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@item strict
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strictly conform to all the things in the spec no matter what consequences
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@item normal
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@item unofficial
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allow unofficial extensions
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@item experimental
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allow non standardized experimental things, experimental
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(unfinished/work in progress/not well tested) decoders and encoders.
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Note: experimental decoders can pose a security risk, do not use this for
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decoding untrusted input.
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@end table
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@end table
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@c man end FORMAT OPTIONS
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@anchor{Format stream specifiers}
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@section Format stream specifiers
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Format stream specifiers allow selection of one or more streams that
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match specific properties.
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The exact semantics of stream specifiers is defined by the
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@code{avformat_match_stream_specifier()} function declared in the
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@file{libavformat/avformat.h} header and documented in the
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@ref{Stream specifiers,,Stream specifiers section in the ffmpeg(1) manual,ffmpeg}.
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@ifclear config-writeonly
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@include demuxers.texi
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@end ifclear
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@ifclear config-readonly
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@include muxers.texi
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@end ifclear
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@include metadata.texi
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