[Realtek ALC887-VD] Playback only through 2 channels by default

[Dan Watkins]

Ubuntu does not detect my 5.1 surround sound[0] by default. In order to get it detected, I have to do the following:

1) Open alsamixer
2) Change the "Channel Mode" setting from "2ch" to "6ch" (there is also a "4ch" setting)
3) `pulseaudio -k`

I have to do this on every boot, as the "6ch" setting is not remembered.

[0] My soundcard and sound system are 5.1, but I actually only have front left, center, right and the subwoofer. This shouldn't affect how Ubuntu acts at all (because it can't know what speakers I have plugged in to my subwoofer), but will mean that I can't report on whether or not rear channels are working as expected.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: alsa-base 1.0.25+dfsg-0ubuntu4
ProcVersionSignature: Ubuntu 3.19.0-30.34-generic 3.19.8-ckt6
Uname: Linux 3.19.0-30-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.5
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: daniel 24007 F.... pulseaudio
CurrentDesktop: Unity
Date: Tue Oct 13 10:23:16 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2014-07-30 (439 days ago)
InstallationMedia: Ubuntu-Server 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.3)
PackageArchitecture: all
SourcePackage: alsa-driver
Symptom: audio
Symptom_AlsaPlaybackTest: ALSA playback test through plughw:PCH successful
Symptom_Card: Built-in Audio - HDA Intel PCH
Symptom_Jack: Green Line Out, Rear
Symptom_PulsePlaybackTest: PulseAudio playback test successful
Symptom_Type: Only some of outputs are working
Title: [MS-7788, Realtek ALC887-VD, Green Line Out, Rear] Playback problem
UpgradeStatus: Upgraded to vivid on 2015-08-24 (49 days ago)
dmi.bios.date: 01/18/2012
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: V2.3
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: H61M-P31 (G3) (MS-7788)
dmi.board.vendor: MSI
dmi.board.version: 1.0
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: MSI
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrV2.3:bd01/18/2012:svnMSI:pnMS-7788:pvr1.0:rvnMSI:rnH61M-P31(G3)(MS-7788):rvr1.0:cvnMSI:ct3:cvr1.0:
dmi.product.name: MS-7788
dmi.product.version: 1.0
dmi.sys.vendor: MSI
modified.conffile..etc.modprobe.d.alsa.base.conf: [modified]
mtime.conffile..etc.modprobe.d.alsa.base.conf: 2015-08-05T11:15:16.899686

[Raymond (superquad-vortex2)]

control.1 {
  iface MIXER
  name 'Channel Mode'
  value '2ch'
  comment {
   access 'read write'
   type ENUMERATED
   count 1
   item.0 '2ch'
   item.1 '4ch'
   item.2 '6ch'
  }
 }

this channel mode control limit the availability of 5.1 since the two input jacks have to retask as output jacks

you need to discuss this issue in alsa-devel mailing list and pulseaudio-discuss mailing list

possible way is to add hook which change channel mode when using surround40, surround51

http://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=src/conf/cards/HDA-Intel.conf;hb=HEAD

similar to

http://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=src/conf/cards/ICH4.conf;hb=HEAD

[Raymond (superquad-vortex2)]

hooks.0 {
                        type ctl_elems
                        hook_args [
                      {
                               name "Channel Mode"
                               preserve true
                               value "6ch"
                                 lock true
                                 optional true
                       }
}

[Raymond (superquad-vortex2)]

you need to add hook to front device and surround40 in order to get back the input jacks after probing surround51

hooks.0 {
   type ctl_elems
   hook_args [
   {
    name "Channel Mode"
    preserve true
    value "2ch"
    lock true
    optional true
   }
}

hooks.0 {
   type ctl_elems
   hook_args [
   {
    name "Channel Mode"
    preserve true
    value "4ch"
    lock true
    optional true
   }

[Raymond (superquad-vortex2)]

http://www.intel.com/support/motherboards/desktop/sb/CS-034198.htm

Audio jack retasking is a feature that allows a jack to support more than one function. For example, the pink audio jack can support microphone input when the system configuration is set to stereo mode, 2-channel, and as Center/LFE or Rear Surround, when set to 6-channel mode.

[Launchpad Janitor (janitor)]

[Expired for alsa-driver (Ubuntu) because there has been no activity for 60 days.]

[Stian Skjelstad (mywave)]

Workaround that seems to work (Ubuntu system with systemd and pulseaudio)

Create this file "~/.config/systemd/user/pulseaudio.preconf.service" with this content

[Unit]
Description=Sound Service PreConf
ConditionUser=!root

[Service]
Type=oneshot
ExecStart=amixer set "Channel mode" "6ch"

[Install]
WantedBy=pulseaudio.service

systemctl --user enable pulseaudio.preconf.service

and restart

This mixer setting should be persistent automatically across reboots. And for pulseaudio integration, it should be able to configure this setting in the GUI

[Joachim R. (jro)]

I have a worse bug : after setting alsamixer to 6ch and restarting pulseaudio, I have no rear sound and no dialog in 5.1 application (I select a 5.1 profile in pulseaudio
+ the sound section in Ubuntu setting pannel is unable to test the speakers (they remain silent while the system sound can actually be played in other manner).
This occurs at least in Ubuntu 20.04 and 21.04