ffmpeg conversion - vp8 with alpha 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=&quot;1&quot; 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?
I took the sample from apple https://developer.apple.com/videos/play/wwdc2019/506/
My command line using on colab was
!ffmpeg -y -i https://devstreaming-cdn.apple.com/videos/wwdc/2019/506lqy7sprpfyo800/506/506_hd_hevc_video_with_alpha.mp4 -s 960x540 -vcodec vp8 -metadata:s:v:0 alpha_mode=&quot;1&quot; c0016_alpha.webm

Hope it matches your scenario.