Kinda bummed that Mastodon won't let you upload straight audio, so I decided to muck around with ffmpeg to make a still-image "video". Let's see how it looks:
@nivex
@lostnbronx did you ever write up your method for this?
Aww, bummer. I get a "Can't play this video" in Tusky. Android must not do VP8.
That worked pretty well. How it's done:
ffmpeg -i image.png -i tt-weasels.opus -acodec copy test.webm
I had already encoded the file with opusenc. If you provide a .wav, leave off the "-acodec copy" and ffmpeg will do the encoding for you.