Coda: imx53 plays video with incorrect colors

[Philipp Zabel]

Hi Fabio,

On Mon, 2021-01-18 at 15:36 -0300, Fabio Estevam wrote:
> Hi Philipp,
> 
> On Mon, Jan 18, 2021 at 12:29 PM Philipp Zabel <p.zabel at pengutronix.de> wrote:
> 
> > Please try forcing decoder output to NV12 instead of I420.
> 
> Your suggestion works, thank you. After applying your IPU patch and
> using this Gstreamer pipeline:
> 
> gst-launch-1.0 filesrc location=/media/clip.mp4 ! qtdemux ! h264parse
> ! v4l2h264dec ! video/x-raw,format=NV12  !  kmssink
> 
> The video is played with correct colors.

Ok, thank you. It looks to me like the I420 issue is either a bug in
coda-dev, or an interaction issue between GStreamer and coda-dev, where
coda-dev doesn't let GStreamer change the format at a point where it
expects to be able to. The b/w image (with slight discolorations in a
regular pattern) could very well be actual NV12 interpreted as I420 by
GStreamer (and thus kmssink). I'll have closer look.

> Can we make the NV12 format be used automatically so that a simple
> 'gst-play-1.0 /media/clip.mp4' works?

That would be a matter of increasing the rank of the NV12 format
in gst_v4l2_object_format_get_rank() above that of I420 and YV12.

> > Yes. Please try if the following patch makes it work:
> 
> With this Gstreamer patch, I don't see the segfault anymore, but it
> plays in black-and-white.

Thanks for testing. I've opened

https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/856

to track this.

regards
Philipp