Archive for March, 2014

David Henningsson

Headset jacks on newer laptops

Headsets come in many sorts and shapes. And laptops come with different sorts of headset jacks – there is the classic variant of one 3.5 mm headphone jack and one 3.5 mm mic jack, and the newer (common on smartphones) 3.5 mm headset jack which can do both. USB and Bluetooth headsets are also quite common, but that’s outside the scope for this article, which is about different types of 3.5 mm (1/8 inch) jacks and how we support them in Ubuntu 14.04.

You’d think this would be simple to support, and for the classic (and still common) version of having one headphone jack and one mic jack that’s mostly true, but newer hardware come in several variants.

If we talk about the typical TRRS headset – for the headset itself there are two competing standards, CTIA and OMTP. CTIA is the more common variant, at least in the US and Europe, but it means that we have laptop jacks supporting only one of the variants, or both by autodetecting which sort has been plugged in.

Speaking of autodetection, hardware differs there as well. Some computers can autodetect whether a headphone or a headset has been plugged in, whereas others can not. Some computers also have a “mic in” mode, so they would have only one jack, but you can manually retask it to be a microphone input.
Finally, a few netbooks have one 3.5 mm TRS jack where you can plug in either a headphone or a mic but not a headset.

So, how would you know which sort of headset jack(s) you have on your device? Well, I found the most reliable source is to actually look at the small icon present next to the jack. Does it look like a headphone (without mic), headset (with mic) or a microphone? If there are two icons separated by a slash “/”, it means “either or”.

For the jacks where the hardware cannot autodetect what has been plugged in, the user needs to do this manually. In Ubuntu 14.04, we now have a dialog:
What-did-you-plug-in
In previous versions of Ubuntu, you would have to go to the sound settings dialog and make sure the correct input and output were selected. So still solvable, just a few more clicks. (The dialog might also be present in some Ubuntu preinstalls running Ubuntu 12.04.)

So in userspace, we should be all set. Now let’s talk about kernels and individual devices.

Quite common with Dell machines manufactured in the last year or so, is the version where the hardware can’t distinguish between headphones and headsets. These machines need to be quirked in the kernel, which means that for every new model, somebody has to insert a row in a table inside the kernel. Without that quirk, the jack will work, but with headphones only.
So if your Dell machine is one of these and not currently supporting headset microphones in Ubuntu 14.04, here’s what you can do:

  • Check which codec you have: We currently can enable this for ALC255, ALC283, ALC292 and ALC668. “grep -r Realtek /proc/asound/card*” would be the quickest way to figure this out.
  • Try it for yourself: edit /etc/modprobe.d/alsa-base.conf and add the line “options snd-hda-intel model=dell-headset-multi”. (A few instead need “options snd-hda-intel model=dell-headset-dock”, but it’s not that common.) Reboot your computer and test.
  • Regardless of whether you manage to resolve this or not, feel free to file a bug using the “ubuntu-bug audio” command. Please remove the workaround from the previous step (and reboot) before filing the bug. This might help others with the same hardware, as well as helping us upstreaming your fix to future kernels in case the workaround was successful. Please keep separate machines in separate bugs as it helps us track when a specific hardware is fixed.

Notes for people not running Ubuntu

  • Kernel support for most newer devices appeared in 3.10. Additional quirks have been added to even newer kernels, but most of them are with CC to stable, so will hopefully appear in 3.10 as well.
  • PulseAudio support is present in 4.0 and newer.
  • The “what did you plug in”-dialog is a part of unity-settings-daemon. The code is free software and available here.