Luma -> Alpha with v1.18

[Nirbheek Chauhan]

On Thu, Jan 6, 2022 at 5:00 AM amindfv--- via gstreamer-devel
<gstreamer-devel at lists.freedesktop.org> wrote:
>
> I'm looking for a way to use the luma plane of one video as the alpha plane of another.
>
> It appears the "alphacombine" element (https://gstreamer.freedesktop.org/documentation/codecalpha/alphacombine.html?gi-language=c) can do this, but it's too new even for the unstable release of GStreamer, and for a variety of reasons I'm stuck on the latest stable (1.18).
>
> What I'm trying to do is also possible in ffmpeg with "extractplanes=y" + "alphamerge".
>
> I'd welcome any way to do this, no matter how much of a hack. Big pipeline? Fine. Somehow using GPU/shaders? No prob.

You can copy the plugin's source code into your project, and then either:

1. Build it as a dynamic plugin and set GST_PLUGIN_PATH to it, or
2. Link to it statically and register it manually with gst_element_register()

This is probably the easiest thing you can do. You can keep syncing
the plugin sources with upstream till you can move to 1.20

Cheers,
Nirbheek