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doc/muxers: tee muxer - rearrange, add notes and general tidy-up

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doc/muxers.texi
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@ -2037,20 +2037,35 @@ ffmpeg -re -i ... -c:v libx264 -c:a aac -f fifo -fifo_format flv -map 0:v -map 0
@anchor{tee}
@section tee
The tee muxer can be used to write the same data to several files or any
other kind of muxer. It can be used, for example, to both stream a video to
the network and save it to disk at the same time.
The tee muxer can be used to write the same data to several outputs, such as files or streams.
It can be used, for example, to stream a video over a network and save it to disk at the same time.
It is different from specifying several outputs to the @command{ffmpeg}
command-line tool because the audio and video data will be encoded only once
with the tee muxer; encoding can be a very expensive process. It is not
useful when using the libavformat API directly because it is then possible
to feed the same packets to several muxers directly.
command-line tool. With the tee muxer, the audio and video data will be encoded only once.
With conventional multiple outputs, multiple encoding operations in parallel are initiated,
which can be a very expensive process. The tee muxer is not useful when using the libavformat API
directly because it is then possible to feed the same packets to several muxers directly.
Since the tee muxer does not represent any particular output format, ffmpeg cannot auto-select
output streams. So all streams intended for output must be specified using @code{-map}. See
the examples below.
Some encoders may need different options depending on the output format;
the auto-detection of this can not work with the tee muxer, so they need to be explicitly specified.
The main example is the @option{global_header} flag.
The slave outputs are specified in the file name given to the muxer,
separated by '|'. If any of the slave name contains the '|' separator,
leading or trailing spaces or any special character, those must be
escaped (see @ref{quoting_and_escaping,,the "Quoting and escaping"
section in the ffmpeg-utils(1) manual,ffmpeg-utils}).
@subsection Options
@table @option
@item use_fifo @var{bool}
If set to 1, slave outputs will be processed in separate thread using @ref{fifo}
If set to 1, slave outputs will be processed in separate threads using the @ref{fifo}
muxer. This allows to compensate for different speed/latency/reliability of
outputs and setup transparent recovery. By default this feature is turned off.
@ -2059,12 +2074,6 @@ Options to pass to fifo pseudo-muxer instances. See @ref{fifo}.
@end table
The slave outputs are specified in the file name given to the muxer,
separated by '|'. If any of the slave name contains the '|' separator,
leading or trailing spaces or any special character, it must be
escaped (see @ref{quoting_and_escaping,,the "Quoting and escaping"
section in the ffmpeg-utils(1) manual,ffmpeg-utils}).
Muxer options can be specified for each slave by prepending them as a list of
@var{key}=@var{value} pairs separated by ':', between square brackets. If
the options values contain a special character or the ':' separator, they
@ -2073,13 +2082,27 @@ must be escaped; note that this is a second level escaping.
The following special options are also recognized:
@table @option
@item f
Specify the format name. Useful if it cannot be guessed from the
output name suffix.
Specify the format name. Required if it cannot be guessed from the
output URL.
@item bsfs[/@var{spec}]
Specify a list of bitstream filters to apply to the specified
output.
It is possible to specify to which streams a given bitstream filter
applies, by appending a stream specifier to the option separated by
@code{/}. @var{spec} must be a stream specifier (see @ref{Format
stream specifiers}).
If the stream specifier is not specified, the bitstream filters will be
applied to all streams in the output. This will cause that output operation
to fail if the output contains streams to which the bitstream filter cannot
be applied e.g. @code{h264_mp4toannexb} being applied to an output containing an audio stream.
Options for a bitstream filter must be specified in the form of @code{opt=value}.
Several bitstream filters can be specified, separated by ",".
@item use_fifo @var{bool}
This allows to override tee muxer use_fifo option for individual slave muxer.
@ -2087,19 +2110,13 @@ This allows to override tee muxer use_fifo option for individual slave muxer.
This allows to override tee muxer fifo_options for individual slave muxer.
See @ref{fifo}.
It is possible to specify to which streams a given bitstream filter
applies, by appending a stream specifier to the option separated by
@code{/}. @var{spec} must be a stream specifier (see @ref{Format
stream specifiers}). If the stream specifier is not specified, the
bitstream filters will be applied to all streams in the output.
Several bitstream filters can be specified, separated by ",".
@item select
Select the streams that should be mapped to the slave output,
specified by a stream specifier. If not specified, this defaults to
all the input streams. You may use multiple stream specifiers
separated by commas (@code{,}) e.g.: @code{a:0,v}
all the mapped streams. This will cause that output operation to fail
if the output format does not accept all mapped streams.
You may use multiple stream specifiers separated by commas (@code{,}) e.g.: @code{a:0,v}
@item onfail
Specify behaviour on output failure. This can be set to either @code{abort} (which is
@ -2113,7 +2130,7 @@ will continue without being affected.
@itemize
@item
Encode something and both archive it in a WebM file and stream it
as MPEG-TS over UDP (the streams need to be explicitly mapped):
as MPEG-TS over UDP:
@example
ffmpeg -i ... -c:v libx264 -c:a mp2 -f tee -map 0:v -map 0:a
"archive-20121107.mkv|[f=mpegts]udp://10.0.1.255:1234/"
@ -2136,23 +2153,19 @@ option is applied to @file{out.aac} in order to make it contain only
audio packets.
@example
ffmpeg -i ... -map 0 -flags +global_header -c:v libx264 -c:a aac
-f tee "[bsfs/v=dump_extra]out.ts|[movflags=+faststart]out.mp4|[select=a]out.aac"
-f tee "[bsfs/v=dump_extra=freq=keyframe]out.ts|[movflags=+faststart]out.mp4|[select=a]out.aac"
@end example
@item
As below, but select only stream @code{a:1} for the audio output. Note
As above, but select only stream @code{a:1} for the audio output. Note
that a second level escaping must be performed, as ":" is a special
character used to separate options.
@example
ffmpeg -i ... -map 0 -flags +global_header -c:v libx264 -c:a aac
-f tee "[bsfs/v=dump_extra]out.ts|[movflags=+faststart]out.mp4|[select=\'a:1\']out.aac"
-f tee "[bsfs/v=dump_extra=freq=keyframe]out.ts|[movflags=+faststart]out.mp4|[select=\'a:1\']out.aac"
@end example
@end itemize
Note: some codecs may need different options depending on the output format;
the auto-detection of this can not work with the tee muxer. The main example
is the @option{global_header} flag.
@section webm_dash_manifest
WebM DASH Manifest muxer.