Sound problems in my Late 2015 iMac

[fox]

This has become the most vexing problem I have faced since converting to Linux. Those of you following my threads about the problems I've had on this Late 2015 5K iMac have already heard about my problems getting distros to boot. These have been solved now, and I have two distros installed (Mint 18.2, Ubuntu 16.04) that have been booting pretty quickly and working pretty well. Until earlier in the week when I discovered the sound problems I haven't been able to solve. They're the same on Mint and Ubuntu: sound in Firefox works well. So does Skype, but I have no sound in Chromium or in any music or video app (rhythmbox, clementine, VLC, player). I don't think this was always the case, and it may be as a result of something I recently installed but if so, I don't know what. Here is the audio output from inxi when running from Linux Mint:

Audio:  Card-1 Advanced Micro Devices [AMD/ATI] Tonga HDMI Audio [Radeon R9 285/380]
           driver: snd_hda_intel bus-ID: 01:00.1
           Card-2 Intel Sunrise Point-H HD Audio
           driver: snd_hda_intel bus-ID: 00:1f.3
           Sound: Advanced Linux Sound Architecture v: k4.8.0-53-generic

Like with the video card problem, I have an onboard and attached audio card. I don't think that's the problem though, first because I do get sound output and second because I can disable the AMD card and it makes no difference. Intuitively, I think that the problem relates to some kind of interference between pulseaudio and alsa, if only that I remember this being a problem that a lot of folks have had in the past. I have tried various online solutions of reloading on or the other, reinstalling one or both, playing with sound settings in sound settings app on gnome or in pulseaudio sound settings. Every once in awhile I actually get it to work, but it doesn't stay working once the music app is closed and reopened, or after a reboot, and whatever trick I have tried doesn't work if I repeat it. I even thought of removing pulseaudio altogether, but removing it threatens to remove a lot of other stuff including the desktop.

I have searched for a solution and tried various possibilities, all to no avail so far. This could be the one problem that either has me going back to the Mac OS on this otherwise great iMac, or has me selling it. If you have a suggestion, I'm all ears!

[Jason]

You probably already checked this but in the volume setting on the menubar or tray, under Sound Settings, you may have a tab for Applications. Try this when you have sound working on one application and not another. Make sure they're both running, I mean. It could be that the sound for particular applications is defaulting to low enough you can't hear it. I only know the steps for doing this in LM Cinnamon but other versions of LM should have similar settings.

[fox]

Thanks, Jason. I did check that and the sound volume on the "oscilloscope" was high enough.

[ssfc72]

Mike, Maybe a small usb sound dongle, would get around this issue. Maybe one of the PLUG members would have one, if you don't.

Bill

[fox]

What's a sound dongle, Bill? Whatever it is, I would gladly try it. I did try plugging in a pair of usb speakers thinking it might be a port issue, but they didn't make any difference at all.

[ssfc72]

A usb sound dongle is a small usb sound card, with audio out and mic in, ports.  It is about the same size as a usb flash drive.

[fox]

Thanks for that, Bill; I didn't know these existed. I assume you plug speakers into them. Not the greatest solution since the speakers in my iMac are much superior to any cheap ones I own, but I would do this if it works. Staples and Best Buy sell cheap models, but they have to be ordered and I don't know whether it would even work. So over to the Club - anyone have a usb sound card I could try out?

[ssfc72]

OK Mike, if no Peterborough PLUG member has a usb sound card dongle, to loan you, then I have one you can try.
I bought it for a project I am going to build, but the dongle doesn't even have a case, just a bare circuit board. Got 2, from ebay for about $3.50 each.

https://www.ebay.ca/itm/CM108-USB-Drive-Free-USB-Sound-Card-Laptop-Computer-External-Sound-Card-Module/272374780193?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

I just tried it on my Mint 18 notebook computer and it works fine, plug and play operation. :-)

[Jason]

I had purchased one for an old PC that my wife is using now. The sound had mysteriously disappeared and then came back. You're welcome to try it. And then you can order one for yourself if it does work. This is the one I have:

https://www.amazon.ca/Sabrent-External-Adapter-Windows-AU-MMSA/dp/B00IRVQ0F8/ref=sr_1_2?ie=UTF8&qid=1511797772&sr=8-2&keywords=sabrent+sound

I'd sell it to you, but I'd like to keep it around for a backup. I also got it for half the price that it costs on Amazon now.

[fox]

Thanks, Bill and Jason; much appreciated. I sure don't mind buying one if it works to solve this problem. Better than giving up on this otherwise great computer (or giving up on using Linux on it). Jason, I saw the Sabrent model you have can be ordered from Staples or Best Buy, so getting one isn't the problem. I just want to know it works.

If one or both of you is coming to PLUG MUG on Thursday and you bring it then, I'll give it back at Monday's meeting. If not and you bring it to the meeting, I'll bring it back at Thursday's PLUG MUG. Thanks!!!

[Jason]

I'll be there Thursday.

[fox]

I am convinced that the problem is somehow linked to pulseaudio, but I have yet to find a viable solution. Based on this article, I tried killing pulseaudio in Mint, and got sound back in rhythmbox. But later after some Firefox and Chromium, the sound no longer worked in rhythmbox. There is something key I am missing, but I think I'm on the right track. I'll be interested to see if the sound dongle makes any difference. I did try earphones this morning, and they didn't bring back the sound.

On Mint 18.3, I noticed that I could get sound in rhythmbox, and change songs and still get sound. I then started Firebox, quit it and went back to rhythmbox. At that point, no sound. Coincidence or is this the pattern I've been looking for? Even if it is, what do I do with that information because I'm always going to be using my browser.

[Jason]

I don't know if it's any help but I happened to find this:

http://www.troubleshooters.com/linux/sound/sound_troubleshooting.htm

[fox]

Thanks, Jason. I hadn't come across this article and it does help to put things into perspective. I'm going to try the unmute command, but I'm pretty sure from using other tools that this isn't the problem. I think I'm down near the bottom, possibly with alsa-pulseaudio conflicts. But I now suspect that the new Firefox might be part of the problem or even THE problem. I discovered this possibility at the end of the day and didn't have time to test out my theory. If I am correct, then the solution might be to either go to an earlier version of FF, stop using it altogether or find a way to alter its configuration settings to eliminate whatever is causing the conflict.

[Jason]

For some reason, I had you as a Chrome user. It's weird to think that Firefox is causing an issue but I don't think a lot of people run Linux on Macs so you might be in new territory here. You could Firefox ESR (Extended Support Release). It's basically the enterprise version. You can think of it as the LTS version of Firefox. I don't know if there is a repo for it.

You could also try disabling Flash and any other media plugs in Firefox to narrow down the problem. Same with Chromium. Also, try turning off hardware acceleration.