Adding pixel shader + overlay on Raspberry Pi with eglglessink/glimagesink

[Matthew Waters]

On 11/05/14 21:46, Michael Tyson wrote:
> Hi folks,
>
> I'm building some stuff based on GStreamer on Raspberry Pi. I'm 
> wanting to (a) display an overlay on top of the video feed and (b) 
> split and possibly distort the incoming video for display on the 
> Oculus Rift. I have been using eglglessink with GST 1.2.3 so far, 
> although I see that that seems to have been superseded recently by 
> glimagesink - it's a bit hard to keep up!
>
> (a) seems to be quite doable, and I've already built some stuff that 
> interacts with the dispmanx API to create display contexts for 
> eglglessink 
> <https://github.com/monsieurpod/raspifpv/blob/master/src/gstreamer_renderer.c> and 
> my own overlay 
> <https://github.com/monsieurpod/raspifpv/blob/master/src/egl_telemetry_renderer.c> and 
> it appears to function adequately.
>
> I'm not sure how to go about (b), however, particularly given recent 
> developments. Seems like glshader/glimagesink would be perfect for 
> this (there's even a _tutorial_ on it!), but gst-plugins-bad 1.3.1's 
> source package isn't in the Raspbian repository yet and given that 
> it's only 8 days old, I wasn't sure if it'd be fully operational yet 
> anyway, on RasPi.
>
> So: Any chance of a pointer, to save me a bit of messing about? Should 
> I be starting to use glimagesink, with a glshader? Is it likely to 
> work with gst_video_overlay_set_window_handle (in order to provide my 
> own graphical context) in a similar way as eglglessink, so I can still 
> use an overlay?

Sure, glimagesink is the way forward for a GL-based video sink however 
it does not seem to have support for the GstVideoOverlay API on the RPI 
[1].  glshader is a little finicky in that it expects a couple of things 
in order to integrate with the video pipeline. Most notably would be the 
texture parameter in order to access the frame data, which is a NPOT 2D 
texture represented by "sampler2D tex" in GLSL.

> Many thanks, and cheers for your ongoing work.
> Michael
[1] 
http://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/gst-libs/gst/gl/dispmanx/gstglwindow_dispmanx_egl.c#n224
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