theodop
Posts: 8
Joined: Wed May 15, 2019 3:41 am

ALSA audio 3.5mm playing mono only

Wed May 15, 2019 3:58 am

Raspberry Pi 3
Ubuntu MATE 1.20.1 / Ubuntu 18.04.2
Kernel 4.15.0-1032-raspi2

I am attempting to use the 3.5mm audio jack for stereo playback but the playback device only ever shows up as mono.

[email protected]:~/Code$ amixer
Simple mixer control 'PCM',0
Capabilities: pvolume pvolume-joined pswitch pswitch-joined
Playback channels: Mono
Limits: Playback -10239 - 400
Mono: Playback -2563 [72%] [-25.63dB] [on]

speaker-text -c2 only plays audio in the "left" phase of the test (but it is played in the center, i.e. both channels).

Audio controls within MATE only show mono also, so I don't think the problem is limited to ALSA, but I only need ALSA audio.

Other posts ( https://www.raspberrypi.org/forums/view ... hp?t=18755 ) indicate that while the ALSA controls only adjust the volume in mono, playback should be in stereo. I have not found this to be the case.

epoch1970
Posts: 2763
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: ALSA audio 3.5mm playing mono only

Wed May 15, 2019 9:47 am

Last time I've checked I've also seen the device reported as mono, but with "-c 2" you could hear "left" and "right" fine.
Is the audio cable fully pushed in the plug?
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

theodop
Posts: 8
Joined: Wed May 15, 2019 3:41 am

Re: ALSA audio 3.5mm playing mono only

Wed May 15, 2019 10:33 am

I've been unplugging and plugging it in all day but if this is the fix for it I will leave tech forever and walk into the ocean

epoch1970
Posts: 2763
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: ALSA audio 3.5mm playing mono only

Wed May 15, 2019 11:19 am

:D
I meant socket, sorry. Anyways, I think it has happened to me more than once.
You can also try with another cable/headset; just in case the plug is somehow not compatible.
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

theodop
Posts: 8
Joined: Wed May 15, 2019 3:41 am

Re: ALSA audio 3.5mm playing mono only

Wed May 15, 2019 10:36 pm

Alas, that doesn't seem to be the issue. I've brought in another pair of headphones to test with as well - no improvement. The plug seems to be mating well with the socket.

I think I'll try another RPi today with my SD card, and another image with my RPi, if I can track it all down.

theodop
Posts: 8
Joined: Wed May 15, 2019 3:41 am

Re: ALSA audio 3.5mm playing mono only

Thu May 16, 2019 8:50 am

The plot thickens - through a HDMI screen, I get sound - but only mono still :(

theodop
Posts: 8
Joined: Wed May 15, 2019 3:41 am

Re: ALSA audio 3.5mm playing mono only

Thu May 16, 2019 8:51 am

To be clear, I have headphones plugged into the screen and the sound output from both ALSA and other applications (such as YouTube) is only mono.

fruitoftheloom
Posts: 19483
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: ALSA audio 3.5mm playing mono only

Thu May 16, 2019 9:14 am

theodop wrote:
Thu May 16, 2019 8:51 am
To be clear, I have headphones plugged into the screen and the sound output from both ALSA and other applications (such as YouTube) is only mono.

So you are not plugging in directly to the Raspberry Pi ?
adieu

My other Computer is an Asus CS10 ChromeBit running Chrome Operating System.
HP Envy 4500 Wireless Printer supported by HPLIP software in Raspbian Stretch.

theodop
Posts: 8
Joined: Wed May 15, 2019 3:41 am

Re: ALSA audio 3.5mm playing mono only

Thu May 16, 2019 9:16 am

Alright, so I don't have a fix for the user environment in Ubuntu, but I DO have a fix for ALSA: the default sound device doesn't work, but plughw:CARD=ALSA,DEV=0 does!

So this:
speaker-test -D plughw:CARD=ALSA,DEV=0 -c2
produces two beautiful earfuls of static.

This is now testing over HDMI, so once I work up the nerve to possibly break it again, I'll test with the 3.5mm jack.

theodop
Posts: 8
Joined: Wed May 15, 2019 3:41 am

Re: ALSA audio 3.5mm playing mono only

Thu May 16, 2019 9:17 am

"So you are not plugging in directly to the Raspberry Pi ?"

I WAS plugged in to the 3.5mm jack, but moved to HDMI to try and eliminate variables. I will test again with the 3.5mm jack soon.

fruitoftheloom
Posts: 19483
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: ALSA audio 3.5mm playing mono only

Thu May 16, 2019 9:43 am

theodop wrote:
Thu May 16, 2019 9:17 am
"So you are not plugging in directly to the Raspberry Pi ?"

I WAS plugged in to the 3.5mm jack, but moved to HDMI to try and eliminate variables. I will test again with the 3.5mm jack soon.

The supported by Raspberry Pi Foundation Operating System is Raspbian, maybe best to try Raspbian to ensure it is not a Ubuntu issue.
adieu

My other Computer is an Asus CS10 ChromeBit running Chrome Operating System.
HP Envy 4500 Wireless Printer supported by HPLIP software in Raspbian Stretch.

theodop
Posts: 8
Joined: Wed May 15, 2019 3:41 am

Re: ALSA audio 3.5mm playing mono only

Thu May 16, 2019 11:51 am

Maybe on the holidays I'll chase this one up. Unfortunately using Raspbian at this stage is not an option as Ubuntu is the supported (read: documented) distro for Intel RealSense.

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