[mythtv-users] Raspberry Pi audio centre and sub swapped

[Peter Bennett]

On 11/26/2017 05:03 PM, Andrew Wilkinson wrote:
> Hi,
>
> I recently tried to start watching the BBC's Blue Planet 2, but 
> unfortunately I have a problem with the audio. It's broadcast in 6 
> channel AAC which my onkyo can't decode, so for the first time I'm 
> using multichannel PCM.
>
> Front left and right, and rear left and right all work fine. The 
> centre and sub woofer are swapped though, which doesn't do David 
> Attenborough's voice any favours. I can confirm this using the speaker 
> test screen, which also uses multichannel PCM.
>
> I'm using a Raspberry Pi and OpenMax audio. Is there any way to 
> correct the channel mapping? I suspect I might be able to use the 
> vcgencmd hdmi_channel_map command, but I've no idea how to generate 
> the correct value.
>
> Any insights you can provide would be much appreciated.
>
> Thanks,
> Andrew
>
>
Does the HDMI connection go direct to the Onkyo? If you are using a 
toslink optical or coax connection, they don't support multi-channel PCM.

Make sure you have selected the correct number of speakers in the 
"Speaker configuration". You can also try switching this between 5.1 and 
7.1. Different selections will change the way the channels are mapped.

Another thing you can try - there are two ways to get digital audio from 
Raspberry pi, using ALSA or OpenMAX audio (see 
https://www.mythtv.org/wiki/Raspberry_Pi#Digital_Audio_with_ALSA and 
https://www.mythtv.org/wiki/Raspberry_Pi#Digital_Audio). I believe the 
ALSA method is superior, so I would try that.

Peter