HTML5 audio starts from the wrong position in Firefox

Question

I'm trying to play an mp3 file and I want to jump to specific location in the file. In Chrome 33 on Windows, the file jumps the correct position (as compared with VLC playing the mp3 locally) but in Firefox 28 on Windows it plays too far forward and in Internet Explorer 11 it plays too far behind.

It used to work correctly in Firefox 27 and earlier.

Is there a better way of doing this?

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EDIT: The problem doesn't even require SoundManager2. You can replicate the same issue with just the <audio> tag in Firefox. These two lines are all the code you need to reproduce it:

<audio autoplay id="audio" src="http://ivdemo.chaseits.co.uk/enron/20050204-4026(7550490)a.mp3" controls preload></audio>
<button onclick="javascript:document.getElementById('audio').currentTime = 10;">Jump to 10 secs "...be with us in, er, 1 minute...  ok" </button>

Try it here: http://jsfiddle.net/cpickard/29Gt3/

EDIT: Tried with Firefox Nightly, no improvement. I have reported it as bug 994561 in bugzilla. Still looking for a workaround for now.

Answer 1

The problem lies in the VBR encoding of the mp3.

Download that mp3 to disk and convert it to fixed bit rate, say with Audacity.

Run the example from disk:

<audio autoplay id="audio" src="./converted.mp3" controls preload></audio>
<button onclick="javascript:document.getElementById('audio').currentTime = 10;">
Jump to 10 secs "...be with us in, er, 1 minute...  ok" </button>

and it works fine for me.

So my suggestion for workaround is is to upload an alternative fixed-bit mp3 file in place of the one you are using. Then it should work in the current FFx.

Answer 2

I work on SoundJS and while implementing audio sprites recently ran into similar issues. According to the spec, setting the position of html audio playhead can be inaccurate by up to 300ms. So that could explain some of the issues you are seeing.

Interestingly, your fiddle plays correctly for me in FF 28 on win 8.1 if I just let it play through from the start.

There are also some known issues with audio length accuracy that may also have an effect, which you can read about here.

If you want precision, I would definitely recommend using Web Audio where possible or a library like SoundJS.

Hope that helps.