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adafruit
Posts: 71
Joined: Sat Apr 28, 2012 3:32 pm
Location: NYC, USA
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what alsa config changes in 2017-11 PIXEL (raspbian stretch full)

Fri Feb 09, 2018 12:24 am

Heya folks, someone let us know that the instructions we have for I2S audio output still work well on raspbian *lite* but not as much on *full*. Last time round, we even had scratch and the menubar vol control working with I2S which was really a beautiful thing.

As of Nov 2017's Raspbian full, I2S audio works, but volume control does not. :? We're debugging it but, things are kinda odd.

For example, after setting up I2S and alsaconfig and rebooting, a ~/.asoundrc appears. This is probably not helping things, but removing it just makes it come back on next reboot. Grepping thru the img file doesnt reveal anything and nothing in /etc either!

Here's hoping whomever is in charge of audio setup & ALSA for PIXEL is around, maybe they can give some hints on what changed :)

spl23
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 411
Joined: Fri Dec 26, 2014 11:02 am

Re: what alsa config changes in 2017-11 PIXEL (raspbian stretch full)

Fri Feb 09, 2018 11:09 am

A default .asoundrc is created when the volume control plugin launches if the currently selected audio output device does not have any available simple controls (and therefore cannot be controlled by the plugin). This isn't new behaviour - it has been the way the plugin works for the last couple of years.

It would be helpful to know which version of the image your hardware did work correctly with, as that would help narrow down the changes. The majority of the changes made to the plugin in the latest release were to improve Bluetooth audio behaviour, but the change which I suspect is causing your issue is the removal of the gstreamer mixer API calls, which was required due to this functionality being removed from gstreamer. I have replaced the functionality which was provided by gstreamer with direct calls to the ALSA API, and I suspect this is the cause of your problem.

The relevant changelist is at https://github.com/raspberrypi-ui/lxplu ... 14990ef81a

The bad news is that I have no idea what it was that gstreamer did which made your hardware work, so I also have no idea how to replicate it in ALSA...

spl23
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 411
Joined: Fri Dec 26, 2014 11:02 am

Re: what alsa config changes in 2017-11 PIXEL (raspbian stretch full)

Fri Feb 09, 2018 11:54 am

FWIW, I've just tried a HifiBerry DAC+ with the latest image, and it works fine - I believe that is also an I2S device, so it looks as if there is nothing inherently broken in I2S audio support in the current image.

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