Correcting Video Levels (Patrick Cusack)

t1mbre at t1mbre at
Sun May 15 17:18:55 UTC 2022

>From: Patrick Cusack <patrickcusack at>
>Subject: Re: Correcting Video Levels
>Message-ID: <CB1F5CF9-40DB-44D1-B9B2-198BB5E11198 at>
>Content-Type: text/plain;	charset=utf-8

> Can you indulge me a little thought experiment? Would it be possible to
use another tool to write yup frames to a socket that GStreamer then uses as
input? Or can you direct me to a plugin example where I cold do the
calculations my self?

> Thanks,

> Patrick

Fifos work.

mkfifo   something
gst-launch-1,0 filesrc location=something blocksize=fill-in-expected-size !
gst-launch-1.0 somepipeline ! filesink location=something

rm something               --- clean up when you're done

> On May 13, 2022, at 1:47 PM, Nicolas Dufresne via gstreamer-devel
<gstreamer-devel at> wrote:
> Le jeudi 12 mai 2022 ? 07:57 -0700, Patrick Cusack via gstreamer-devel a
?crit :
>> GStreamer team,
>> I am capturing video using a BlackMagic Video device, sending out 
>> using a VP9 encoder, and then using a payloader for use with webRTC. 
>> When I view the stream, my blacks and whites are mapped 16-235 
>> instead of 0-255. Is there a way to correct this? WIth ffmpeg, I can 
>> use a filter graph and and set the input and output scale
> I don't think our converters current handle this, but the range is 
> part of the colorimetry= filed in caps. Would be nice to fix this of 
> course, range conversion seems pretty handy.
>> Thanks,
>> Patrick


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