[gst-devel] Adding alpha or transparency to video

[Jonathan Wong]

Hi,

Thanks for the info!

 > However, not all videosinks and video codecs support such colorspaces, so
 > that depends on what you are planning to do with the video.

Play it in a Qt widget, on Windows, then on Linux.

Any idea which videosink or codecs do support alpha channel? Has anyone done this before to show 
it works? At some point, I'll try every codec or sink there is to find out.

In DirectShow, I could get 2 videos playing, one on top of the other. The top one is transparent. 
I can even get it to play inverted (and other cool transforms). Hoping to do just that with GStreamer.

LRN wrote:
> Jonathan Wong wrote:
>> Hi,
>>
>> I forgot to mention I need it on Windows (and then Linux later).
>>
>> I found this: http://pbx.mine.nu/effectv/ (a port of effectv to win32, using DirectShow no less)
>>
>> I am hoping to programmatically make a video stream semi-transparent (alpha channel).
>>   
> GStreamer (GstBuffer) supports colorspaces with alpha-channel. Adding
> transparency is as simple as converting your video to the right
> colorspace (AYUV or RGBA) using ffmpegcolorspace element and then
> changing the alpha values to something other than default (this could be
> done by your own element, or by existing one, if you manage to find it).
> However, not all videosinks and video codecs support such colorspaces,
> so that depends on what you are planning to do with the video.
> 
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