Blacks appear as 'fickery white' when compositing certain sized images

[Duncan Palmer]

This problem is caused by the videobox element, which I had been using
because I needed Y444 support at one point. I don't now, and can use
videocrop instead, which doesn't exhibit this issue.

On 16 June 2016 at 15:41, Duncan Palmer <dunk.palmer at gmail.com> wrote:

> Hi,
>
> I have a pipeline I use to compose a video stream from multiple cameras.
> I've found a problem whereby blacks appear as 'flickery white' in the
> resulting image. This problem only appears when I blend using pixel formats
> which contain an alpha channel, and using images below a certain height.
>
> The following example feeds a 1280x577 stream to the compositor, and does
> not exhibit the problem;
>
> gst-launch-1.0 uridecodebin uri=file://`pwd`/b.1.mkv ! videobox  top=143
> ! videorate  ! 'video/x-raw,framerate=25/1,format=AYUV' !   compositor  !
> glimagesink
>
> The following example feeds a 1280x576 stream to the compositor, and does
> exhibit the problem (the '576' is a bit of a red flag perhaps?).
>
> gst-launch-1.0 uridecodebin uri=file://`pwd`/b.1.mkv ! videobox  top=144
> ! videorate  ! 'video/x-raw,framerate=25/1,format=AYUV' !   compositor  !
> glimagesink
>
> I'm still digging, but feel this could take some time. Can anyone offer
> suggestions or point me in a direction for investigation? The problem
> occurs with both the software and gl compositors.
>
> Note: I force the used of an alpha pixel format in the pipeline above, to
> produce a small example, but in practice I insert the alpha element. I'm
> also showing only one video source; in practice I use more.
>
> Cheers,
> Dunk
>
>
>
>
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