Hi Daniel,
Hi Volker,
On 9 May 2017 at 12:32, Volker Vogelhuber
<v.vogelhu...@digitalendoscopy.de> wrote:
On 09.05.2017 12:59, Philipp Zabel wrote:
You create two separate EGLImages, calling eglCreateImage once for each
plane. See for example:
https://cgit.freedesktop.org/gstreamer/gst-plugins-bad/tree/gst-libs/gst/gl/gstglupload.c#n646
or
https://cgit.freedesktop.org/wayland/weston/tree/libweston/gl-renderer.c#n1536
That assumes I have two planes available. But as mentioned the planes
are created internally by dri2_create_image_dma_buf during my call of
eglCreateImage.
So from the API point of view I only have one FD from the V4L2 buffer that
is of type
FOURCC('Y','U','Y','V'). Passing that FD to eglCreateImage returns only one
EGLImage.
Although understanding gstreamer code is always a bit hard, I think in their
case they have
a mulit plane V4L2 buffer, where I only have a single plane buffer.
What Philipp is suggesting is that you import the same plane to an
EGLImage twice: once as DRM_FORMAT_RG8 and once as
DRM_FORMAT_ARGB8888. This gives you two EGLImages, which you bind to
two separate texture units / samplers: you sample the Y channel from
the DRM_FORMAT_RG8 image (ignoring the other channel), and you sample
the U and V channels from the DRM_FORMAT_ARGB8888 image (ignoring the
other two channels). This is what GStreamer and Weston do when
confronted with such a buffer, and it does work.
That's why I wonder if there is a way to retrieve the "second" EGLImage
after eglCreateImage
has been called for the single V4L2 DMABUF file descriptor.
There is not a way to do this.
Ah, OK, now I got it. Thanks! I guess the DRM_FORMAT_ARGB8888
width parameter has to be half the original width, as I only have 16bit
per pixel.
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