This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

This thread was archived. Please ask a new question if you need help.

Why are MP4 video playback problems solved when the MP4 is converted to M4V?

  • 1 reply
  • 2 have this problem
  • 2 views
  • Last reply by guigs

FXFx
FXFx
more options

Something weird is happening with my website's MP4 videos in Firefox (39.0.3), using the videojs html5 player. For example, in a 4-minute video: sometimes there is no audio; sometimes the audio starts but cuts out after 30 seconds; sometimes the last 30 seconds of audio starts playing after the first 30 seconds. This behaviour is only seen (or heard) in files accessed off the server - accessed off the C-drive, they play fine.

The MP4-with-audio-problems was created from a .MOV file using Handbrake 0.10. I noticed that other MP4s I did last year (with Handbrake 0.09) do not have audio problems in Firefox. So it may be a Handbrake issue?

Anyway, workaround! I converted the same .MOV to .M4V (using Handbrake) and the audio problems have disappeared. It's odd, because M4V is supposedly the exact same file as the MP4 - only the extension is different. But it works.

Something weird is happening with my website's MP4 videos in Firefox (39.0.3), using the videojs html5 player. For example, in a 4-minute video: sometimes there is no audio; sometimes the audio starts but cuts out after 30 seconds; sometimes the last 30 seconds of audio starts playing after the first 30 seconds. This behaviour is only seen (or heard) in files accessed off the server - accessed off the C-drive, they play fine. The MP4-with-audio-problems was created from a .MOV file using Handbrake 0.10. I noticed that other MP4s I did last year (with Handbrake 0.09) do not have audio problems in Firefox. So it may be a Handbrake issue? Anyway, workaround! I converted the same .MOV to .M4V (using Handbrake) and the audio problems have disappeared. It's odd, because M4V is supposedly the exact same file as the MP4 - only the extension is different. But it works.

All Replies (1)

guigs
guigs
more options

This might have to do with it: