I'm trying to convert a mov file (with alpha channel) to webm, vp8 with alpha, on windows.
ffmpeg -i C0016.mov -s 960x540 -vcodec vp8 -pix_fmt yuva420p -metadata:s:v:0 alpha_mode="1" c0016_alpha.webm
gives me:
[NULL @ 00000204af221e80] Unable to find a suitable output format for 'c0016_alpha.webm' c0016_alpha.webm: Invalid argument
How can I fix it?