User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:77.0) Gecko/20100101 Firefox/77.0

Steps to reproduce:

1. run firefox in terminal
2. open soundcloud.com and start a track

I can reproduce this only on my Arch linux laptop with version 77.0.1 but on my Ubuntu laptop the sound plays fine on soundcloud.com with the same FF version.

Actual results:

3. got this message: [Child 6895, MediaDecoderStateMachine #1] WARNING: Decoder=7f041f506400 Decode error: NS_ERROR_DOM_MEDIA_FATAL_ERR (0x806e0005) - RefPtr<MediaSourceTrackDemuxer::SamplesPromise> mozilla::MediaSourceTrackDemuxer::DoGetSamples(int32_t): manager is detached.: file /build/firefox/src/firefox-77.0.1/dom/media/MediaDecoderStateMachine.cpp, line 3370
   3a. sometimes there is no error coming but the no sound issue is there.
4. no sound plays (in the same browser instance youtube plays fine)

Expected results:

there should be no error and the sound should be audible when playing soundcloud.com just as when i play youtube.

i did now downgrade to FF 76.0.1 and the issue is gone = sound plays in soundcloud. Updated back again to 77.0.1 and the issue is back again = no sound.

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Thanks for the report!
Could you try to find a regression range (if there is one)?

$ pip3 install --upgrade mozregression
$ mozregression --good 76 --bad 77 -a https://soundcloud.com/

If you get tab crashes, you could append --pref security.sandbox.content.level:0 to disable the sandbox (insecure).

Dear Jan,

i installed the mozregression but what is the use of it if you just open soundcloud and don't play any sound?
both versions were 'good' but my problem is a no sound issue when trying to play trough soundcloud.

(In reply to e3k from comment #4)

Dear Jan,

i installed the mozregression but what is the use of it if you just open soundcloud and don't play any sound?
both versions were 'good' but my problem is a no sound issue when trying to play trough soundcloud.

Of course you need to play music on Soundcloud each time Firefox opens to test whether audio works or not. Just replace that example soundcloud link with one of an actual song, so that you have less to click.

It's also possible that the bug has been backported from Nightly 78 to Beta 77, for example. Mozregression only opens Nightly versions.
$ mozregression --good 76 --bad 78 -a https://soundcloud.com/asalhani/bbc-news-countdown-full-musicopening-voice-version

(e3k from comment #1)

i did now downgrade to FF 76.0.1 and the issue is gone = sound plays in soundcloud. Updated back again to 77.0.1 and the issue is back again = no sound.

First check that the link you are testing against is broken in your regular 77.0.1.

ok i did what you say but this time i get problem playing sound on all 76 77 and 78. With the difference that soundlcound reports all the time "there was an error playing this track"

Arch linux

Then it sounds more like an issue with a system library. If you downgrade Firefox to 76.0.1 (comment 1), do other packages get downgraded as well? Do you have a package update log and could try to narrow it down?

@Jan. no when doing the upgrade no other packages besides firefox are downgraded or upgraded. there are 3 after install hooks running but no seem to be multimedia related:

systemd
gtk-icon-cache
desktop-database

We would remove (refine) that error message in bug1613672, but I think no sound was being played is another issue.

What's the audio backend in your Arch Linux? We only support PulseAudio for now. Could you provide your about:support?
Does audio work on other sites like youtube? or soundcloud is the only place you cannot hear the sound?

If the problem only occurs when playing Soundcloud.com, could you disable the webaudio and see if the issue is sovled?

Steps to disable webaudio:

1. Go to about:config
2. Search dom.webaudio.enabled
3. Set dom.webaudio.enabled to false
4. Relaunch your Firefox and play Soundcloud.com again

@C.M.Chang. Bingo! after disabling dom.webaudio.enabled i can finally play sound at FF+Arch Linux. What is it how does it work? and why does it make sound stop on soundcloud?

Paul, does Firefox rely on specific library that can cause this issue?

Please attach a copy of about:support.

Thanks, this is because you're using Alsa.

thanks for supporting me at least i have a workaround now.