@Megalomaniak said:
Well, all I can offer as a thought is that webm is a container and not a codec, so the question is what codecs were used in it?
I used this script from stackoverflow to convert mp4, which keeps reasonable quality at a small size:
#!/bin/bash
# Usage: ./mp4towebm video.mp4
ffmpeg -y -i $1 -b:v 0 -crf 30 -pass 1 -an -f webm /dev/null
ffmpeg -i $1 -b:v 0 -crf 30 -pass 2 ${1%%.*}.webm
Don't know if it indicate the codec info. If not, maybe you can figure out from above google drive,
