[gst-devel] 2x2 videowall pipeline

[Luciana Fujii Pontello]

On Thu, 2010-11-18 at 15:40 +0000, David Balch wrote:
> Hi,

> gst-launch-0.10 v4l2src device=/dev/video0 !
> video/x-raw-yuv,width=320,height=240 ! queue ! videomixer name=mix !
> ffmpegcolorspace ! autovideosink \
>   videotestsrc pattern="green" ! video/x-raw-yuv,width=320,height=240
> ! videobox left=-320 border-alpha=0 ! ffmpegcolorspace ! queue ! mix.
> \
>   videotestsrc pattern="blue" ! video/x-raw-yuv,width=320,height=240 !
> videobox top=-240 border-alpha=0 ! ffmpegcolorspace ! queue ! mix. \
>   videotestsrc pattern="red" ! video/x-raw-yuv,width=320,height=240 !
> videobox left=-320 top=-240 border-alpha=0 ! ffmpegcolorspace ! queue
> ! mix.
> 
> Unfortunately, the webcam doesn't actually show - it's corner is just
> black. (The webcam works with "gst-launch-0.10 v4l2src
> device=/dev/video0 ! video/x-raw-yuv,width=320,height=240 !
> autovideosink".)

It seems like the property border-alpha is not working for you because
your video doesn't have alpha channel. Add an alpha element in every
video like this: videotestsrc pattern="blue" !
video/x-raw-yuv,width=320,height=240 ! alpha ! videobox top=-240
border-alpha=0 ! queue ! mix.

(I think you can remove some of the colorspaces as well)

Regards,

Luciana Fujii