My specific use case is using vpx_codec_decode to decode a WEBM video file that has an embedded alpha channel.
Does VP9 support an alpha channel? Is the YUVA420p video format viable in the libvpx library? There is a little bit of code that references the alpha channel, but it doesn't appear to do anything. (VPX_PLANE_ALPHA, VPX_IMG_FMT_HAS_ALPHA)
Is there a special flag that I need to set before compiling the VPX library in order to enable alpha channel support?