[FFmpeg-user] Encode VP9 (or VP8) WITH alpha channel

[Wagner Patriota]

Is FFmpeg supporting encoding of WebM with VP9 (or VP8) with alpha channel
through libvpx?

I tried the very basic:
ffmpeg -i input.mov -vcodec libvpx-vp9 output.webm

but nothing happens... my video doesn´t get the transparency from
input.mov... any hints?

Thank you,
Wagner