Many embedded videos not working

[larryedwards]

I just found that a problem I have had for months is linked to Good Twitter and similar extensions (Old Twitter, Twitter Old UI). If I have any one of them enabled some embedded videos in tweets will not play. In all cases the static image appears very briefly on-screen, and the I get a gray video area saying "We cannot play the video in this browser. Please try a different web browser". If I disable the extension, then all videos work correctly.

I have Win7 and (always) the latest Firefox update. In Web Console for problem tweets, this is the error message: [Quote]
Cannot play media. No decoders for requested formats: video/mp4; codecs="avc1.42E01E mp4a.40.2", video/quicktime; codecs="avc1.42E01E mp4a.40.2", video/x-m4v; codecs="avc1.42E01E mp4a.40.2", video/mp4; codecs="avc1.42E01E mp4a.40.2", video/quicktime; codecs="avc1.42E01E mp4a.40.2", video/x-m4v; codecs="avc1.42E01E mp4a.40.2", application/x-mpegURL, video/mp4; codecs="avc1.42E01E mp4a.40.2"
[End Quote]

That's all I know. Willing to work with you on troubleshooting this.