Arch Linux

mot.def

Member

Registered: 2011-07-03

Posts: 19

HDMI audio out with Bumblebee?

I have a Thinkpad T430i with an Nvidia NVS 5400M card that I've got running with the proprietary Nvidia drivers and Bumblebee. I've got HDMI video out working by using intel-virtual-output and xrandr but audio's just coming out of the laptop speakers.

First, I checked alsamixer to see if there was a channel for the HDMI port but I only had controls for analogue channels. aplay gives:

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC3202 Analog [ALC3202 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

indicating no digital output. I wasn't sure if the Nvidia card or Intel chipset is responsible for digital output so I booted into Windows, checked the playback devices menu and found that HDMI audio was coming out of the Nvidia card. However, lspci in Linux doesn't list this device, even with the graphics card switched on with bbswitch.

I then switched to discrete graphics mode and tried aplay again:

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: PCH [HDA Intel PCH], device 0: ALC3202 Analog [ALC3202 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 7: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 8: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 9: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

So clearly my system has support for the audio device somewhere, but it's not starting up with Bumblebee. I noticed that the HDMI sound module isn't loaded with my system but enabling it doesn't give me access to the Nvidia audio interface.

I've looked around online for a solution but it seems most people at least see their digital output where I don't - I figured the best place to start with this issue is actually getting my system to detect the digital output. Any ideas?

mot.def

Member

Registered: 2011-07-03

Posts: 19

Re: HDMI audio out with Bumblebee?

Comparing the output of lspci between Optimus and discrete mode, I found that

01:00.1 Audio device: NVIDIA Corporation GF108 High Definition Audio Controller (rev a1)

was absent in Optimus, so I know the address of the device I want to enable at least. I checked it against the ALSA soundcard matrix and found it uses the snd-hda-intel module but I already have that loaded for my analogue card. ls -l /dev/snd shows several missing entries in Optimus mode compared to discrete. I wonder if maybe I first need to switch the graphics card on using bbswitch, and then somehow have my system rescan the PCI slots to find the new audio device, but I can't figure out how I might do that without simply rebooting the computer, which would just switch the GPU off again anyway.