hello johnfrogladd, could you provide a sample site where this problem is apparent?

Sure, it's a site in development at the minute.

http://www.karmacloud.co.uk/beta/

You will unfortunately have to create an account to get to the homepage...sorry about that :/

The music should play on load of the homepage once logged in. I have some debug output in the console if you'd like to monitor what exactly is going on.

Thanks for looking into this Phillip. Very much appreciated :)

that's what i've found out so far: when a audio file should start playing on your site & you look into the web console, you see that the appropriate file is fetched from the soundcloud source - you can copy its source address, paste it into a new tab and the mp3 file will play just fine there, so it shouldn't be an issue with codecs or media.windows.-media-foundation.enabled.

in further testing i discovered that when you disable media.webaudio.enabled, your site will throw an error message but play the file fine afterwards. i understand too little about how the source code on your site works, but that would indicate to me that you're using the web audio api as default (which for whatever reason isn't working in firefox) and html5 audio as a fallback...

i don't know much about the web audio api either, so i'm not sure if there's a bug in firefox that prohibits proper playback or if it's an implementation issue on the site. maybe some of the documentation can help: https://developer.mozilla.org/en-US/docs/Web_Audio_API & https://developer.mozilla.org/en-US/docs/Web_Audio_API/Porting_webkitAudioContext_code_to_standards_based_AudioContext

i don't know if you'd be comfortable by that, but i could also post the login data of my test account here publicly, so that other contributors can have a look at it too - maybe someone more knowledgeable stumbles across a solution...

Thanks Phillipp for your reply. I really do appreciate the time you took looking into this.

You are correct in that when media.webaudio.enabled is disabled I am falling back to Soundcloud's HTML5 widget. I have code set up to detect the lack of mp3 support and fall back to the widget.

I thought I was facing an issue in fetching the mp3 from soundcloud itself - but in the network tab in developer tools I can see it is doing a successful GET on the mp3... It is very strange I have to say.

I want to use the WebAudio API in order to setup visualisers on the site like I have done so on Chrome. 

Feel free to post details in case anyone else might know! I'll keep investigating on my own for the meantime!

Many Thanks! John

ps: Thanks for the links :D

ok, so the username/pw combo for the test account would be firefox123

Thought I'd update you on the matter.

I've found that the error is in the GET. The url set for the mp3 gets modified by Soundcloud (some sort of callback). Soundcloud fetches the track and callsback a new url which is then used as the source in the audio element.

Now, I've compared both audio objects in Chrome and on Firefox - both contain the same URL - it's just that Firefox somehow isn't picking up the mp3 in the callback.

I really think this is a bug and I it's very easy to see how this went unnoticed. Anyway, I'm sure I'll figure out a workaround.

Thanks for all your help Phillip.