VP9 video encoded by AWS MediaConvert will play in Chrome but not Firefox
I have recently used AWS MediaConvert to create a webm video file using the VP9 codec.
This file will play for me locally using VLC and ffplay. It will also play in Chrome (either locally or from the web).
However it will not play in Firefox. Error is "Video cannot be played because the file is corrupt" and the console shows "Media resource http://s3-eu-west-1.amazonaws.com/lg-watch/ff-test_fromaws.webm could not be decoded, error: Error Code: NS_ERROR_DOM_MEDIA_FATAL_ERR (0x806e0005)"
But if I encode the same file via VP9 codec using ffmpeg then the file will play perfectly in firefox.
Using mediainfo to examine the files I cannot see any difference in them. Can anyone help me understand what is preventing the AWS video from playing?
Test files:
(this is the one that won't play, encoded using AWS Mediaconvert with default settings for VP9/webm) http://s3-eu-west-1.amazonaws.com/lg-watch/ff-test_fromaws.webm
(this is the one that will play, encoded using ffmpeg with default settings - -c:v libvpx-vp9 -b:v 2M) http://s3-eu-west-1.amazonaws.com/lg-watch/ff-test-from_ffmpeg.webm
Firefox v83 (Fedora 33, Wayland)