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doc/ffmpeg: document trailing "?" in map option

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This feature was added in 2375a85c36.

Signed-off-by: Lou Logan <lou@lrcd.com>
This commit is contained in:
Lou Logan 2017-02-13 15:26:43 -09:00
parent c1a5fca06f
commit 1c049d5ffe
1 changed files with 13 additions and 1 deletions
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doc/ffmpeg.texi
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@ -871,7 +871,7 @@ Set the size of the canvas used to render subtitles.
@section Advanced options
@table @option
@item -map [-]@var{input_file_id}[:@var{stream_specifier}][,@var{sync_file_id}[:@var{stream_specifier}]] | @var{[linklabel]} (@emph{output})
@item -map [-]@var{input_file_id}[:@var{stream_specifier}][?][,@var{sync_file_id}[:@var{stream_specifier}]] | @var{[linklabel]} (@emph{output})
Designate one or more input streams as a source for the output file. Each input
stream is identified by the input file index @var{input_file_id} and
@ -887,6 +887,11 @@ the source for output stream 1, etc.
A @code{-} character before the stream identifier creates a "negative" mapping.
It disables matching streams from already created mappings.
A trailing @code{?} after the stream index will allow the map to be
optional: if the map matches no streams the map will be ignored instead
of failing. Note the map will still fail if an invalid input file index
is used; such as if the map refers to a non-existant input.
An alternative @var{[linklabel]} form will map outputs from complex filter
graphs (see the @option{-filter_complex} option) to the output file.
@var{linklabel} must correspond to a defined output link label in the graph.
@ -924,6 +929,13 @@ To map all the streams except the second audio, use negative mappings
ffmpeg -i INPUT -map 0 -map -0:a:1 OUTPUT
@end example
To map the video and audio streams from the first input, and using the
trailing @code{?}, ignore the audio mapping if no audio streams exist in
the first input:
@example
ffmpeg -i INPUT -map 0:v -map 0:a? OUTPUT
@end example
To pick the English audio stream:
@example
ffmpeg -i INPUT -map 0:m:language:eng OUTPUT