tcat
Posts: 32
Joined: Wed Oct 18, 2017 11:23 am

Analog Audio No Stereo?

Mon Jun 11, 2018 6:50 am

Hi,

How do I set analog audio to output stereo sound on PI3 B?
I use amplified speakers powered from USB.

$ aplay /usr/share/sounds/alsa/Side_Left.wav
$ aplay /usr/share/sounds/alsa/Side_Right.wav

The above plays to both channels on PI3 B, while on PI1 B played left or right.
Many thanks
Tomas

epoch1970
Posts: 4206
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: Analog Audio No Stereo?

Mon Jun 11, 2018 10:46 am

I've noticed that, too. I don't remember it was that way.
I think if you force 2 channels, e.g. aplay -c 2 ... you get stereo
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

tcat
Posts: 32
Joined: Wed Oct 18, 2017 11:23 am

Re: Analog Audio No Stereo?

Mon Jun 11, 2018 11:02 am

Hi,

Thank you for taking your interest, actually even with `-c2' option

$ aplay -c2 /usr/share/sounds/alsa/Side_Left.wav
$ aplay -c2 /usr/share/sounds/alsa/Side_Right.wav

audibly outputs to both speakers.

$ amixer
Simple mixer control 'PCM',0
Capabilities: pvolume pvolume-joined pswitch pswitch-joined
Playback channels: Mono
Limits: Playback -10239 - 400
Mono: Playback -281 [94%] [-2.81dB] [on]

The above seems same for both PI1 and PI3, I know mono is a bit misleading as per discussion here:
viewtopic.php?t=15028#p154050

Many thanks.
Tomas

tcat
Posts: 32
Joined: Wed Oct 18, 2017 11:23 am

Re: Analog Audio No Stereo?

Mon Jun 11, 2018 7:29 pm

Hi,

I just played this mp4 test file using `omxplayer', it is left-right stereo test mp4 stream.
It just plays stereo, so no problem at all.

https://youtu.be/dG3MrGB0JPM

Tomas

tcat
Posts: 32
Joined: Wed Oct 18, 2017 11:23 am

Re: Analog Audio No Stereo?

Mon Jun 11, 2018 7:41 pm

Hi,

I have also found these two mp3 files useful to test with omxplayer.
Tarball will extract to Downloads folder.

$ tar -xzf sounds.tgz
$ omxplayer ~/Down*/left.mp3
$ omxplayer ~/Down*/right.mp3

Tomas
Attachments
sounds.tgz
(131.98 KiB) Downloaded 15 times

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