White frames with v4l2 source & GstGLUploadElement

[Nicolas Dufresne]

Le mardi 26 avril 2016 à 21:58 +0200, Gottfried Haider a écrit :
> I am trying to make an application [1] that uses GStreamer's GL API
> in
> a very similar way to the testegl.c [2] example work with v4l2
> sources, but I am only getting white frames.
> 
> The code previously had a playbin with uri=file:///..., which worked.
> Now I am trying uri=v4l2:///dev/video0, which points to a webcam.
> 
> Running "gst-launch-1.0 playbin uri=v4l2:///dev/video0" in the
> terminal also works, and shows reasonable images from the camera.
> 
> Is there anything obvious that I am missing here? (I see the format
> is
> YUY2 all the way to the end of the pipeline, is this perhaps what
> needs changing?)
> 
> I uploaded a DOT file [3], as well as the debug output [4] when using
> the webcam. The same for playing back a regular H.264 encoded video
> file as well [5].
> 
> Thanks for any leads!

Sorry that it took a while before someone answer this one. There is
nothing obvious in your pipeline that could explain white frames.
Sounds like GL incompatibility issue. Which GStreamer version are you
using ? What is the paltform / GL stack involved here ?

For the from-file case, you'll notice you are using omxdecoder with
EGLImage support, that is much easyer to render on screen, as you only
have to bind the EGLImage to a texture and display it. While in the
v4l2 case, you have raw image that you need to upload and transform
using shaders.

cheers,
Nicolas
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