[FFmpeg-devel] [PATCH] ffmpeg: implement input file stream disabling

Michael Niedermayer michael at niedermayer.cc
Wed Dec 12 21:20:03 EET 2018

On Wed, Dec 12, 2018 at 10:25:46AM +0530, Gyan wrote:
> On 12-12-2018 03:40 AM, Michael Niedermayer wrote:
> >On Mon, Dec 10, 2018 at 08:57:44PM +0530, Gyan wrote:
> >>At Michael's suggestion, this patch lets -vn/-an/-sn/-dn work for input
> >>files. Individual streams can still be let through e.g.
> >>
> >>     ffmpeg -an -discard:a:1 none -i file ...
> >>
> >>will let (only) the 2nd audio stream be seen during stream selection and
> >>filtergraph construction.
> >>
> >>Thanks,
> >>Gyan
> >>  ffmpeg_filter.c |    7 +++++++
> >>  ffmpeg_opt.c    |   17 +++++++++++++++++
> >>  2 files changed, 24 insertions(+)
> >>212c7bcecbd62329f3f18893c71f464ebeee3b67  0001-ffmpeg-implement-input-file-stream-disabling.patch
> >> From 9823a71f2055f2c4c4484536291bbd2afee36a81 Mon Sep 17 00:00:00 2001
> >>From: Gyan Doshi <ffmpeg at gyani.pro>
> >>Date: Mon, 10 Dec 2018 20:38:20 +0530
> >>Subject: [PATCH] ffmpeg: implement input file stream disabling
> >>
> >>-vn/-an/-sn/-dn can be set to stop processing of streams
> >>of said type from an input file.
> >isnt this 2 seperate changes ?
> >one is adding -vn/-an/-sn/-dn input support and the other is fixing some input
> >discard issues related to existing -discard functionality
> Only one change. I provided an example command syntax to show how to
> selectively enable streams while leaving others of the same type disabled.

You misunderstand me i think
patches should be split in self contained changes.
part of this patch adds support for -vn/-an/-sn/-dn
and other parts are fixing bugs

the patch for example adds a error check for disabled filter inputs
using this example:
ffmpeg -discard all  -i tests/data/asynth-44100-1.wav -i tests/data/asynth-44100-1.wav -filter_complex '[0:a][1:a]amerge=inputs=2[aout]' -map '[aout]'  -f framecrc -

This newly added code triggers and prints
"Stream specifier ':a' in filtergraph description [0:a][1:a]amerge=inputs=2[aout] matches a disabled input stream."

before the patch the code did not error out.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No human being will ever know the Truth, for even if they happen to say it
by chance, they would not even known they had done so. -- Xenophanes
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