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

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Duncan Palmer-2

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

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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Duncan Palmer-2

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

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 <[hidden email]> 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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Nicolas Dufresne-5

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

Le 16 juin 2016 8:37 PM, "Duncan Palmer" <[hidden email]> a écrit :
>
> 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.

If not already done, please file a bug. Though in general videobox is slow and can be replaced with crop and compositor.

>
> On 16 June 2016 at 15:41, Duncan Palmer <[hidden email]> 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
>>
>>
>>
>
>
> _______________________________________________
> gstreamer-devel mailing list
> [hidden email]
> https://lists.freedesktop.org/mailman/listinfo/gstreamer-devel
>

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