v4l2src and dynamic image/jpeg

Nicolas Dufresne nicolas at ndufresne.ca
Mon Aug 28 17:43:05 UTC 2017

Le samedi 19 août 2017 à 22:39 -0500, Matteo Valdina a écrit :
> Hi,
> It is probably a basic question but I didn't find a good answer.
> I'm trying to write a Bin that it is something like:
> v4l2src ! capsfilter! vaapijpegdec ! srcpad
> I would like to add and remove jpeg decoder if my target resolution
> requires image/jpeg or x-raw. 
> For example, I have some camera that provides image/jpeg and other
> that provide I420.
> How can I approach this problem?
> Should I configure the caps filter with image/jpeg and I420 and use a
> probe query_downstream/upstream to dynamically link/remove the
> jpegdec?

You could use decodebin, it will passthrough on raw caps. Something
like this will set the preference to jpeg:

gst-launch-1.0 -v v4l2src device=/dev/video1 ! "image/jpeg;video/x-raw" ! decodebin ! glimagesink

> There is a simpler approach for that?
> Best
> Matteo
> -- 
> “There are two ways of constructing a software design: One way is to
> make it so simple that there are obviously no deficiencies, and the
> other way is to make it so complicated that there are no obvious
> deficiencies. The first method is far more difficult.”
> - Tony Hoare
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> gstreamer-devel at lists.freedesktop.org
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