.webm video plays in Chrome and Opera but not Firefox

Question

I converted some .mp4 files to .webm with Miro. They play in Chrome and Opera but they do not play in Firefox 16. Firefox has supported .webm since FF 4. I tested video.canPlayType() and it returns "probably". I know that the MIME types are correct in .htaccess. I downloaded the a test .webm file from html5rocks and uploaded it to the same server and it played fine in FF, which makes me think it must be the encoding. I tried converting the videos multiple times and still no dice. Can anyone think of what would cause the them to not work in FF? Is there a more reliable way to convert videos to .webm?

Chrome_ImF.webm <== works in FF

amber-miro.webm <== does not work in FF

costa-miro.webm <== does not work in FF

Answer 1

There seems to be no problem with the encoding, however there are some errors with the file format on the webm files you created with Miro. I suggest using ffmpeg.

I've tested amber.webm which you provided as a sample. I used ffmpeg to re-format it into webm, without encoding, using the commandline:

ffmpeg -i amber.webm -acodec copy -vcodec copy amber1.webm

And the resulting file seems to play well in Firefox.

To directly convert .mov to .webm via ffmpeg you can use:

ffmpeg -i amber.mov -qscale 0 amber.webm

-qscale 0 is meant to retain the highest quality. See the ffmpeg docs.

Answer 2

The issue is in the version of ffmpeg included with MVC 3.0 on windows. It appears that it's skipping frames at the beginning of the webm conversion.

To workaround this issue for now, you can download an updated version of ffmpeg for windows from here: http://ffmpeg.zeranoe.com/builds/.

Extract the files and copy the updated ffmpeg.exe file here: C://Program Files/Participatory Culture Foundation/Miro Video Converter/ffmpeg/ replacing the outdated ffmpeg.exe file.

After that your webm conversions with Miro Video Converter should work fine on Firefox.