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[bcmpinc <bcmpinc@xxxxxxxxxxx>]

I've been running into this problem over and over again and found
several different solutions. However, some of them also stopped working
after installing updates. There is this solution that I found when using
the NVIDIA proprietary drivers: http://askubuntu.com/a/511907/73753.
Which involves suspending your laptop, to trick it into powering on the
audio chip on your nvidia gpu.

However, I seriously recommend using the nouveau driver nowadays. As it
supports the nvidia optimus technology, whereas the proprietary driver
does not. Though, the drawback is that the nouveau driver only supports
opengl 3.3. See http://nouveau.freedesktop.org/wiki/Optimus/. The
difference is that you use `DRI_PRIME=1` instead of `optirun`. And that
you use `echo DDIS > /sys/kernel/debug/vgaswitcheroo/switch` instead of
`prime-select nvidia` before restarting X11 when you want to use the
hdmi output.

With nouveau, my hdmi audio still does not work out of the box. Though, the audio device is listed in lspci -H1 when booted, which saves us half the trouble we had with the NVIDIA driver. The steps I use to get the driver loaded for the audio device are (warning, this might hang your pc, also, if your pc fails to (re)boot, perform a hard-reset by removing the power & battery and waiting 3 or more minutes (1 minute is not sufficient)):
- press ctrl+alt+f1
- login and run `sudo su`
- shut down x11 and the loginscreen, such that the gpu is no longer in use. I could do that by running `runlevel` followed by `init 3`
- 'remove' the gpu: `echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/remove`
- redetect the gpu: `echo 1 > /sys/bus/pci/rescan`
- If everything went right, the driver for the hdmi audio chip should be loaded. Verify this by running `lscpi` and checking if there is a line like "01:00.1 Audio device: NVIDIA Corporation GF116 High Definition Audio Controller (rev a1)".
- switch to the hdmi output: `echo DDIS > /sys/kernel/debug/vgaswitcheroo/switch`
- start the login manager and x11 again: in my case I needed to run `init 5` where 5 was the number reported by `runlevel`.

I obtained the remove & rescan pci trick from
https://devtalk.nvidia.com/default/topic/609790/linux/no-hdmi-sound-w
-optimus-in-linux/.

-- 
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to alsa-driver in Ubuntu.
https://bugs.launchpad.net/bugs/1377653

Title:
  HDMI sound output not detected / NVIDIA optimus laptop

Status in alsa-driver package in Ubuntu:
  Confirmed

Bug description:
  Hi,

  not sure if this is an alsa or nvidia/nouveau bug.
  HDMI audio output doesn't appear in sound settings output panel.
  Audio works well on internal speakers, but it seems there is no way to make it output to hdmi...

  The laptop has optimus NVIDIA+Intel.
  The behaviour is the same with nouveau or nvidia proprietary driver.

  Please let me know if further testing is required

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: alsa-base 1.0.25+dfsg-0ubuntu4
  ProcVersionSignature: Ubuntu 3.13.0-36.63-generic 3.13.11.6
  Uname: Linux 3.13.0-36-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 2.14.1-0ubuntu3.5
  Architecture: amd64
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  sam        2295 F.... pulseaudio
  CurrentDesktop: Unity
  CurrentDmesg: Error: command ['sh', '-c', 'dmesg | comm -13 --nocheck-order /var/log/dmesg -'] failed with exit code 1: comm: /var/log/dmesg: Permission denied
  Date: Sun Oct  5 17:05:35 2014
  InstallationDate: Installed on 2014-04-21 (166 days ago)
  InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
  PackageArchitecture: all
  SourcePackage: alsa-driver
  Symptom: audio
  Title: PCI/internal sound card not detected
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 11/02/2012
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: N56VZ.215
  dmi.board.asset.tag: ATN12345678901234567
  dmi.board.name: N56VZ
  dmi.board.vendor: ASUSTeK COMPUTER INC.
  dmi.board.version: 1.0
  dmi.chassis.asset.tag: No Asset Tag
  dmi.chassis.type: 10
  dmi.chassis.vendor: ASUSTeK COMPUTER INC.
  dmi.chassis.version: 1.0
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrN56VZ.215:bd11/02/2012:svnASUSTeKCOMPUTERINC.:pnN56VZ:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnN56VZ:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
  dmi.product.name: N56VZ
  dmi.product.version: 1.0
  dmi.sys.vendor: ASUSTeK COMPUTER INC.

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