Yeah, I tried that command too and it gave me the same error message.
I took a closer look at ffmpeg's terminal output and it mentioned that avconv was intended to be its replacement, as ffmpeg is no longer maintained. Luckily enough, it appeared to have already been installed on my machine as part of the libav-tools package. So running:
avconv -i input.ogv output.webm
took a while longer than under ffmpeg, but the end result did not have the same visual issues. I'll be switching to using that now.
Yeah, I tried that command too and it gave me the same error message.
I took a closer look at ffmpeg's terminal output and it mentioned that avconv was intended to be its replacement, as ffmpeg is no longer maintained. Luckily enough, it appeared to have already been installed on my machine as part of the libav-tools package. So running:
avconv -i input.ogv output.webm
took a while longer than under ffmpeg, but the end result did not have the same visual issues. I'll be switching to using that now.