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fftools/ffmpeg_demux: implement -bsf for input

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Previously bitstream filters could only be applied right before muxing,
this allows to apply them right after demuxing.
This commit is contained in:
Anton Khirnov
2023-12-13 17:59:39 +01:00
parent 6cb7295abf
commit ae06111d74
6 changed files with 165 additions and 22 deletions
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22
doc/ffmpeg.texi
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@@ -2093,13 +2093,13 @@ an output mpegts file:
ffmpeg -i inurl -streamid 0:33 -streamid 1:36 out.ts
@end example
@item -bsf[:@var{stream_specifier}] @var{bitstream_filters} (@emph{output,per-stream})
Apply bitstream filters to matching streams.
@item -bsf[:@var{stream_specifier}] @var{bitstream_filters} (@emph{input/output,per-stream})
Apply bitstream filters to matching streams. The filters are applied to each
packet as it is received from the demuxer (when used as an input option) or
before it is sent to the muxer (when used as an output option).
@var{bitstream_filters} is a comma-separated list of bitstream filter
specifications. The specified bitstream filters are applied to coded packets in
the order they are written in. Each bitstream filter specification is of the
form
specifications, each of the form
@example
@var{filter}[=@var{optname0}=@var{optval0}:@var{optname1}=@var{optval1}:...]
@end example
@@ -2107,12 +2107,22 @@ Any of the ',=:' characters that are to be a part of an option value need to be
escaped with a backslash.
Use the @code{-bsfs} option to get the list of bitstream filters.
E.g.
@example
ffmpeg -i h264.mp4 -c:v copy -bsf:v h264_mp4toannexb -an out.h264
ffmpeg -bsf:v h264_mp4toannexb -i h264.mp4 -c:v copy -an out.h264
@end example
applies the @code{h264_mp4toannexb} bitstream filter (which converts
MP4-encapsulated H.264 stream to Annex B) to the @emph{input} video stream.
On the other hand,
@example
ffmpeg -i file.mov -an -vn -bsf:s mov2textsub -c:s copy -f rawvideo sub.txt
@end example
applies the @code{mov2textsub} bitstream filter (which extracts text from MOV
subtitles) to the @emph{output} subtitle stream. Note, however, that since both
examples use @code{-c copy}, it matters little whether the filters are applied
on input or output - that would change if transcoding was happening.
@item -tag[:@var{stream_specifier}] @var{codec_tag} (@emph{input/output,per-stream})
Force a tag/fourcc for matching streams.