[FFmpeg-devel] On libavfilter: A Summary of Issues

Clément Bœsch ubitux at gmail.com
Mon Oct 8 20:14:07 CEST 2012

On Sat, Oct 06, 2012 at 09:34:05PM -0600, Michael Bradshaw wrote:
> Thanks for that list. I summarizes many of my own thoughts.
> On Sat, Oct 6, 2012 at 5:38 PM, Derek Buitenhuis <derek.buitenhuis at gmail.com
> > wrote:
> > Is it supposed to be an extensible filtering framework that 3rd
> > party devs write filters for and use for a lot of video processing,
> > like Avisynth and VapourSynth? Is it supposed to be something to
> > mainly be used as a C API from others' applications? Just ffmpeg.c?
> >
> This one in particular gets me. I use the C API of libav* and rarely use
> the command line ffmpeg, but many of the libavfilter filters are quite
> useless in the C API. Take, for example, the silencedetect filter.
> Detecting silence is useful, and I would certainly use it, but all that
> filter does is print it out to the console. Is it meant to be useful only
> to ffmpeg.c (and even then... how useful is that?), or in the C API as
> well? In other words, the ability to get data *out* of libavfilter is
> severely lacking in the C API, so I'm not even sure if it's targeting the C
> API or not.

It's been a long time we're talking about that, and since it seems no one
is going to fix that, I'm trying to do that at the moment (metadata

I'm going to use it in silencedetect and ebur128 to start with, maybe
select for the scene detection as well (to store the scene detect score
for each frame).

Also, I guess it will have to be done in blackdetect/blackframe and

About the re-usage of these metadata, I can think of volume re-using
ebur128, and maybe select re-using these meta (like if the ref has a
select=true meta or something, set by a blackdetect for example).

ffprobe should be able to dump in any fancy output for users to re-exploit
these meta.

Any other potential filter or idea in mind?

Clément B.
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