Posts: 3
Joined: Wed May 13, 2020 12:46 pm

Pi 4 HDMI Audio channel mapping

Wed May 13, 2020 1:40 pm


I have been having trouble with my Pi4 with surround audio channel mapping.
When playing any multichannel audio either from an audio or video file the channels sometimes seem to be randomly mapped to any speaker.

For example, if I set my Audio channel configuration in Kodi to 5.1 or 7.1 and try to play the same file, 5 times out of 10 the front right audio will come from the rear right speaker for example with the front left coming from the front right while it will work fine for the other 5 times.
This happens while decoding to LPCM on the Pi through my AVR or even skipping the AVR and plugging directly to the TV, using headphones I can clearly hear a random channel (eg center) playing in my right headphone while the rear right will play in my left headphone instead of having the left channel mapped to my left headphone and the right channel to my right headphone.

This happens with either Raspbian with kernel 4.19.97-v7l or the 5.4 branch, and also with the latest stable LibreELEC.

Code: Select all

BCM2711 detected
BOOTLOADER: up-to-date
CURRENT: Thu 16 Apr 17:11:26 UTC 2020 (1587057086)
 LATEST: Thu 16 Apr 17:11:26 UTC 2020 (1587057086)
 FW DIR: /lib/firmware/raspberrypi/bootloader/critical
VL805: up-to-date
CURRENT: 000137ad
 LATEST: 000137ad
The same happens from the shell when running speaker-test -c6 or speaker-test -c8 and there seems to be no issue with channel mapping while using stereo.

My Pi2 works perfectly in the same setup with OSMC.

Does anybody have any idea where to start looking to fix this?

Posts: 681
Joined: Tue Mar 11, 2014 6:18 pm
Location: Porto, Portugal
Contact: Website

Re: Pi 4 HDMI Audio channel mapping

Sat May 23, 2020 9:35 pm

Which version are your HDMI cables, 1.4 or 2.0 ? How long is your HDMI cables ? Do you have others to test, the shorter the better.

Posts: 3
Joined: Wed May 13, 2020 12:46 pm

Re: Pi 4 HDMI Audio channel mapping

Sun May 24, 2020 5:15 am

Hey Rascas, thanks for the reply (and thanks for the Kodi build).
I'm using the official raspberry pi micro HDMI to HDMI 1m cable, I'm not sure which version it is but I guess it should be able to provide enough bandwidth as it is able to pass a 4k60fps signal, as a test (I usually output 1080p resolution), as well as a 5.1 24bit 96khz audio recording with no issue apart from the channels being swapped sometimes.
As a comparison the Pi2 is not able to play these files without the audio skipping or playing at a very low speed (as it should, I wasn't expecting it to work).

This is the reason why I didn't bother testing with a different cable but if you still think it could be cable related I could buy a new one to test.

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