cmi8738 very loud on surround

[Igor Korcek]

Release
----------
Ubuntu 12.04 LTS

Package Version
---------------------

pulseaudio 1.1

Hardware
------------

  Generic C-Media 8738 7.1
  5.1 Speaker system

pci:5
          description: PCI bridge
          product: MCP67 PCI Bridge
          vendor: NVIDIA Corporation
          physical id: 8
          bus info: pci@0000:00:08.0
          version: a2
          width: 32 bits
          clock: 66MHz
          capabilities: pci ht subtractive_decode bus_master cap_list
          resources: ioport:d000(size=4096)
        *-multimedia
             description: Multimedia audio controller
             product: CM8738
             vendor: C-Media Electronics Inc
             physical id: 8
             bus info: pci@0000:01:08.0
             version: 10
             width: 32 bits
             clock: 33MHz
             capabilities: pm bus_master cap_list
             configuration: driver=snd_cmipci latency=32 maxlatency=24 mingnt=2
             resources: irq:19 ioport:d800(size=256)

Configuration
-----------------

 "Sound Preferences -> Output" is set to use "Analog Surround 5.1 Output" for the CM8738 device

Expected Result
---------------------

 The master volume should control both the front and the rear and the center/sub speakers

Actual Result
-----------------

 The master volume control only controls the front speakers. The real speakers are set to FULL volume - very loud and can't be changed.

Other
-------

BTW: In 11.04 soundcard works great but after update to 11.10 and after that to 12.04 there is problem again.

Additional info from recursice bug from 10.10: https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/632389

 A bit of searching turned up the following text at http://alsa.opensrc.org/index.php/Cmipci#4.2F6_Multi-Channel_Playback

"WARNING

When "Four Channel Mode" switch is off, the output from rear speakers will be FULL VOLUME regardless of Master and PCM volumes. This might damage your audio equipment. Please disconnect speakers before your turn off this switch. "

If I didn't have a separate master volume switch on the speakers themselves, this would have happened to me.

Being as Sound Preferences itself doesn't seem to have the "4 channel mode" switch, I installed gnome-alsamixer. This does show the "Four Channel Mode" setting. However, when pulsedaemon is running, it is not possible to select the switch. If I kill pulsedaemon, the switch can be enabled and the speakers act as expected (I used speakertest to prove this).

This problem has existed ever since the introduction of Pulse as the default.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

Thank you for reporting this bug to Ubuntu.
Ubuntu 12.04 (precise) reached end-of-life on April 28, 2017.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test.

[Launchpad Janitor (janitor)]

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