Author Archive

David Henningsson

Turn your mic jack into a headphone jack!

Most of today’s built-in sound cards are to some degree retaskable, which means that they can be used for more than one thing. That means you can turn your Mic jack into an extra Headphone jack, or why not make them both line outs, and connect them to your surround receiver?

I’ve known for a while that the kernel exposes an interface that makes it possible to retask your jacks, but almost no one seems to use it, or even know about it. So over the past few weeks I’ve been working (from time to time) with HDA-Jack-Retask, a small application that makes this interface easy to use.

Although primarily meant for power users, it focuses on simplicity: Just select your codec, then select which pins you want to override and what you want them to override to: Headphones, Line Out, Mic, Line In, and so on. There are buttons for trying it out right away, and for making your override the boot-time default. And of course, a button for removing all overrides in case things did not go as planned.

Consider it beta quality for now, and it’s one of those “won’t work for everyone” programs, but that’s mostly due to hardware and driver limitations.

It’s available for Ubuntu 11.10, and you can install it by adding ppa:diwic/hda and then installing the hda-jack-retask package. Start it by running “hda-jack-retask” in a terminal. Enjoy!

David Henningsson

Independent volume for headphones and speakers

If you take Ubuntu Brainstorm’s word for it, one of the more popular wishes for Ubuntu, is to avoid having to adjust the volume slider up and down as you plug and unplug your headphones, but instead keep separate volumes stored for both.

Long story short, it’s a desirable feature, and we’re moving in that direction, but slowly, as the feature is more complex than it seems like at first glance.

The good news: in the upcoming Ubuntu Oneiric (11.10), this is actually working. The bad news: it isn’t working for everyone.

For external stuff, mainly USB and Bluetooth devices, this has been working for a quite a few releases now (although you might have to manually switch to your new card when you plug it in). So let’s restrict the discussion to internal sound cards, that on a typical laptop would control your internal speaker and your 3.5mm headphone jack. Here’s where Oneiric will make a positive difference for many of you (although, still far from all of you).

PulseAudio has the concept of “ports” (in your Gnome “Sound settings”, this is what’s labeled a “Connector”), and headphones and speakers would be different ports of the same card. As of Oneiric, every port has its volume stored independently, so when you switch ports, the volume will automatically change.
Now, this does not become really useful until this port can automatically switch back and forth when you plug and unplug your headphones. This feature is also now implemented in Oneiric, as you can read about in my previous blog post, PulseAudio with jack detection.

Things are not always that easy. Not everyone has just internal speakers and headphones, some have line outs instead, or all three. On the input side, some have internal mics, microphone jacks (often more than one), line ins, or any combination of those. In addition, people are different: some want headphones to automatically mute line outs, others don’t. That’s a typical case where different drivers expose very different behaviour: some do, some don’t, some have a setting you can control in alsamixer. Some drivers enable the user to have different volumes for different outputs, others don’t. Drivers label volume controls and jacks differently. Not every driver actually exposes the current jack sense state to userspace, either.

The bottom line: Is this working for you? Great! Is it not? You’re not alone. I’ll try to fix some of that up for Ubuntu 12.04, but there will – no doubt – be users who won’t have this functionality for a long time. At this point, the best you can do is to file a bug using the “ubuntu-bug audio” command, and hope for the best. Even if it might be too late for your hardware to be supported in 11.10, filing the bug sooner rather than later might help to get it into 12.04. However, manpower is always an issue, so even better would be if you could write a kernel patch yourself to fix it. :-)

David Henningsson

PulseAudio with jack detection

Jack detection in PulseAudio is now in Ubuntu 11.10. This means that PulseAudio will know whether you have plugged in your headphones, mic or HDMI cable, and be able to use that information. Most computers have automute already (i e, speakers mute when you plug in headphones), but this functionality is done entirely in the kernel. With PulseAudio now knowing about this, it can decide that your main volume control will adjust the headphones volume when you have headphones plugged in, and the speaker volume when you don’t.

HDMI adds one more twist to it. Due to hardware design, there are often several “false” ports accompanying the real one(s). And there is no way of knowing which one is right, except through jack detection. So you might see four different HDMI’s in the user interface, but only one is right, and with the jack detection, the right HDMI output will automatically be selected when you activate the HDMI device.
Speaking of the “Sound Preferences” user interface, I hope that we will have an improved user interface for Ubuntu 12.04, that can hide the HDMI devices that are unavailable.
(Also note that for NVidia and ATI cards, binary drivers are often needed to enable HDMI audio, as well as activating the display, through nvidia-settings or the “Displays” settings dialog.)

All of this won’t work for everyone from the start, as it will need support from the ALSA driver. However, for those who don’t have that support, things will not regress compared to the current handling. Hopefully I will be able to improve that situation for some of you in the 12.04 cycle.

Finally, a note on the upstream status of the patches needed for this functionality:

  • The PulseAudio patches will hopefully be merged into PulseAudio, once PulseAudio 1.0 is out. Until then, you can grab the latest patch set here.
  • A udev patch required to enable PulseAudio to read the input devices was rejected upstream.
  • A kernel patch used to identify HDMI input devices is pending upstream review/approval.