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Bug 3052

Summary:	KMix does not properly unmute sound in the presence of PulseAudio
Product:	TDE	Reporter:	Jan Stolarek <jwstolarek>
Component:	tdemultimedia	Assignee:	Michele Calgaro <michele.calgaro>
Status:	RESOLVED FIXED
Severity:	normal	CC:	bugwatch, jwstolarek, michele.calgaro, q4os
Priority:	P5
Version:	R14.0.x [Trinity]
Hardware:	amd64
OS:	Debian Buster
Compiler Version:		TDE Version String:
Application Version:		Application Name:
Bug Depends on:
Bug Blocks:	2247

Description Jan Stolarek 2019-10-11 04:18:43 CDT

This is a long-standing bug that I have finally found time to report. On my laptop when I press the "Mute" button sound is muted properly. In particular, in Kmix:

  - tray icon changes to show "no sound"
  - master channel is set to "off" (the one that is visible after clicking LMB on KMix tray icon)
  - upon opening KMix window, "Master" and "Speaker" channels are set to "off" and "Headphones" channel is set to "on" in the "HDA Intel PCH" section (selected via a combo-box); selecting "PulseAudio" from the said combo box displays a single "Master" channel, which is also set to "off".

When I now press the "Mute" button again I would expect that all the "off" channels mentioned above will switch to "on", but only the "Master" channel in the "HDA Intel PCH" section switches to "on". Everything else remains as described above (including the tray icon) and there is no sound. To unmute the sound I now have to:

  - manually switch on all the channels that are set to "off", or
  - click the tray icon with the middle mouse button, or
  - unmute the sound using PulseAudio mixer (pavucontrol)

Some googling reveals a similar problem already reported for other sound mixers, and the cause is reported to be the fact that the mixer communicates directly with Alsa rather than via PulseAudio. I have tested that the problem disappears when PulseAudio is removed from the system. See here: https://bugs.freedesktop.org/show_bug.cgi?id=79911#c3

Comment 1 Jan Stolarek 2019-10-11 04:23:27 CDT

I think this might be a duplicate of #1505 and perhaps #2782 is also related.

Comment 2 Q4OS Team 2019-10-11 05:07:59 CDT

I can confirm this bug for the most of TDE systems with Pulseaudio installed. It's not possible to unmute the sound using kmix, I need to use PulseAudio mixer (pavucontrol), as described by the OP.

Comment 3 Jan Stolarek 2020-05-14 04:34:21 CDT

Here's an interesting observation, and perhaps a hope for an easy fix. Repeatedly muting and unmuting PulseAudio mixer with dcop (dcop kmix Mixer-1 toggleMute 0) works as intended.

Comment 4 Jan Stolarek 2020-05-15 04:36:14 CDT

I have to take back what I said above. For whatever reason the initial state of the sound mixers on my PC tends to be random at start, e.g. PulseAudio mixer can be muted, while the Alsa mixer is not*. The reason why the above dcop incantation worked was simply because I got lucky and both Pulse and Alsa were unmuted at boot and the dcop incantation handled the muting in an expected way. After a reboot things are back to the state originally described in this bug report.

A different incantation that I found, and that has worked consistently for me across several reboots, is "amixer set Master toggle".

* I suspect this is from a weird interaction with Windows, which I boot into once in a while and which does seem to be able to switch the hardware states of my audio card in ways that are beyond control of Linux. But this is irrelevant here.

Comment 5 Michele Calgaro 2020-05-24 23:59:52 CDT

Marking this bug resolved, as it has now been addressed. The fix will be in the R14.1.0 release.
For additional info see:
- bug 2782
- bug 2783
- bug 3110
- PR https://mirror.git.trinitydesktop.org/gitea/TDE/tdemultimedia/pulls/19
- PR https://mirror.git.trinitydesktop.org/gitea/TDE/tdeutils/pulls/26
- PR https://mirror.git.trinitydesktop.org/gitea/TDE/tdemultimedia/pulls/20

Some code has been backported to R14.0.x and will make KMix able to correctly unmute PA master from the slider's LED.

Further info from mailing list at http://trinity-users.pearsoncomputing.net/?0::17130, including possible work arounds in R14.0.x if needed.