Bug 5.1 Surround issue after pausing Raspberry Pi 4
#1
Dear Forum,

I use the latest Kodi on Debian Buster on my RaspberryPi 4. I adjusted all the audio settings so I could enjoy 5.1 Surround and it seems to works fine.
However, after pausing the video for a couple of seconds (or more) the center channnel suddenly switches to the right or left channel.

This can be fixed (during playback) whenever switch around between the output configuration options. There seems to be no particular setting that does the trick it just helps shuffeling back and forth between these options (best match, optimised, fixed). Eventually the center channel is back on track.

Am I doing something wrong? Does anybody have an idea on how to approach this best?
Thank you very much!
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#2
Is passthrough an option? If your receiver/TV supports it then you won't get any channel swaps when enabled.
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#3
(2020-05-20, 16:56)popcornmix Wrote: Is passthrough an option? If your receiver/TV supports it then you won't get any channel swaps when enabled.

Thank you for your suggestion. I just tried that. Unfortunately that does not seem to help the problem.
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#4
(2020-05-21, 11:13)curiousnoob Wrote:
(2020-05-20, 16:56)popcornmix Wrote: Is passthrough an option? If your receiver/TV supports it then you won't get any channel swaps when enabled.

Thank you for your suggestion. I just tried that. Unfortunately that does not seem to help the problem.       

What audio codec are you playing ?  (Dolby Digital / AC3, Dolby Digital + / E-AC3, DTS, Dolby True HD, DTS HD Master Audio, DTS HD High Resolution Audio, FLAC, AAC, PCM etc.?)

What audio codec does your AVR say it is receiving when you have passthrough for that codec enabled and when you have passthrough disabled?

if you have proper passthrough enabled then it's not really possible for the Pi to alter the audio channel mapping - as it is simply 'passing through' the compressed multichannel bitstream from the source file untouched, for the receiver to decode.

Are you running LibreElec or Kodi under Raspbian.
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#5
I have the exact same issue:
- Raspberry Pi4 connected to Denon AVR 2331ci
- Rasbian Buster (latest) with Kodi 18.6
- Number of channels: 7.1
- Output configuration: Best Match
- Allow Passthrough: Off (to get HD audio)

It randomly happens on diverse content. Hard to reproduce. When stopping and starting content again it usually is solved.
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#6
I'm hoping it's fixed on Kodi 18.7 which is not released yet for Raspbian Buster(?). From the release notes:
Quote:Audio
Fixes around multi-channel audio track support
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#7
(2020-05-21, 11:33)noggin Wrote: What audio codec are you playing ?  (Dolby Digital / AC3, Dolby Digital + / E-AC3, DTS, Dolby True HD, DTS HD Master Audio, DTS HD High Resolution Audio, FLAC, AAC, PCM etc.?)

What audio codec does your AVR say it is receiving when you have passthrough for that codec enabled and when you have passthrough disabled?

if you have proper passthrough enabled then it's not really possible for the Pi to alter the audio channel mapping - as it is simply 'passing through' the compressed multichannel bitstream from the source file untouched, for the receiver to decode.

Are you running LibreElec or Kodi under Raspbian. 
I tried various codecs. If pass through is enabled my receiver displays them (DTS, DD, DD+,...) When passthrough is diabled it shows PCM only.
Problem occurs both with and without passthrough enabled.
I am runnnig a headless Raspbian buster (lastest) with Kodi 18.6.

@Puck: looking forward to the 18.7 to see whether it will be fixed.
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#8
(2020-05-22, 11:59)curiousnoob Wrote: tried various codecs. If pass through is enabled my receiver displays them (DTS, DD, DD+,...) When passthrough is diabled it shows PCM only.
Problem occurs both with and without passthrough enabled.
I am runnnig a headless Raspbian buster (lastest) with Kodi 18.6.

@Puck: looking forward to the 18.7 to see whether it will be fixed. 

If channels are swapping with passthrough active, then it is impossible that the Pi/Kodi is causing it. It must be a problem in your receiver.
If the audio is encoded as DTS/DD/DD+ and we are using passthrough, then the audio is passed untouched to receiver which decodes and outputs it.
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#9
(2020-05-22, 11:59)curiousnoob Wrote:
(2020-05-21, 11:33)noggin Wrote: What audio codec are you playing ?  (Dolby Digital / AC3, Dolby Digital + / E-AC3, DTS, Dolby True HD, DTS HD Master Audio, DTS HD High Resolution Audio, FLAC, AAC, PCM etc.?)

What audio codec does your AVR say it is receiving when you have passthrough for that codec enabled and when you have passthrough disabled?

if you have proper passthrough enabled then it's not really possible for the Pi to alter the audio channel mapping - as it is simply 'passing through' the compressed multichannel bitstream from the source file untouched, for the receiver to decode.

Are you running LibreElec or Kodi under Raspbian. 
I tried various codecs. If pass through is enabled my receiver displays them (DTS, DD, DD+,...) When passthrough is diabled it shows PCM only.
Problem occurs both with and without passthrough enabled.
I am runnnig a headless Raspbian buster (lastest) with Kodi 18.6.

@Puck: looking forward to the 18.7 to see whether it will be fixed.  
If passthrough is enabled then the Raspberry Pi and Kodi are not altering the audio bitstream (*) - it's passed straight from the video file to the receiver in compressed from and isn't altered by Kodi or the Pi.  If you are absolutely sure that you are getting audio channel swaps with passthrough enabled then that points the finger at your amp - but it might be useful to post a log when you are playing a file in passthrough to let people here analyse that the file is definitely being played with passthrough.

(*) If you have transcode enabled then other audio formats that can't be passed-through  will be decoded and then re-encoded by Kodi to AC3/Dolby Digital.  If this is happening then Kodi IS processing the audio (and it's not being passed through)
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#10
I've been having same issue with similar setup (Yamaha RX-V477 receiver with 5.1 output) for about 6 months now. Seeking in videos is triggering this even when bitstreaming is enabled.
I eventually switched to SPDIF optical output with this: https://www.tindie.com/products/Beni_Ska...cal-audio/
Also looking forward to seeing if 18.7 fixes this.
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#11
I wonder if some AVRs are getting confused by some kind of interruption in a passed-through bitstream and this is causing them to do something funny?
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#12
This doesn't seem to be related to Kodi as the same issue occurs for every sound output regardless of the program used. Even speaker-test displays the same problem.
It could be the AVR, I'm not sure as the same setup works fine with a Pi2, only the Pi4 seems to have this issue.
I posted the problem with more detail on the raspberrypi forums: https://www.raspberrypi.org/forums/viewt...8&t=273949

I also tried to patch the kernel with the following thinking it could be related but I was wrong. https://github.com/raspberrypi/linux/com...e57464497e
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#13
(2020-05-23, 15:03)Axionkt Wrote: This doesn't seem to be related to Kodi as the same issue occurs for every sound output regardless of the program used. Even speaker-test displays the same problem.
It could be the AVR, I'm not sure as the same setup works fine with a Pi2, only the Pi4 seems to have this issue.
I posted the problem with more detail on the raspberrypi forums: https://www.raspberrypi.org/forums/viewt...8&t=273949

I also tried to patch the kernel with the following thinking it could be related but I was wrong. https://github.com/raspberrypi/linux/com...e57464497e

Your post in the Pi Forums was about LPCM multichannel - @Crythe reports it with bit streaming (which is much trickier to understand)
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#14
(2020-05-23, 18:28)noggin Wrote:
(2020-05-23, 15:03)Axionkt Wrote: This doesn't seem to be related to Kodi as the same issue occurs for every sound output regardless of the program used. Even speaker-test displays the same problem.
It could be the AVR, I'm not sure as the same setup works fine with a Pi2, only the Pi4 seems to have this issue.
I posted the problem with more detail on the raspberrypi forums: https://www.raspberrypi.org/forums/viewt...8&t=273949

I also tried to patch the kernel with the following thinking it could be related but I was wrong. https://github.com/raspberrypi/linux/com...e57464497e

Your post in the Pi Forums was about LPCM multichannel - @Crythe reports it with bit streaming (which is much trickier to understand)  
Yes I understand the difference, I was merely posting this in case it provided more information as you seemed to think the audio might not be pass through even if it was enabled.
I could try with bit streaming and post the log but as the Pi isn't able to bitstream HD audio would it be able to provide more information as the conditions wouldn't be the same since only the DTS core would be sent to the AVR?
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#15
(2020-05-23, 15:03)Axionkt Wrote: This doesn't seem to be related to Kodi as the same issue occurs for every sound output regardless of the program used. Even speaker-test displays the same problem.
It could be the AVR, I'm not sure as the same setup works fine with a Pi2, only the Pi4 seems to have this issue.
I posted the problem with more detail on the raspberrypi forums: https://www.raspberrypi.org/forums/viewt...8&t=273949

I also tried to patch the kernel with the following thinking it could be related but I was wrong. https://github.com/raspberrypi/linux/com...e57464497e
Thank you for the repost.
I am afraid I wasn't very precise:
I do occasionally use the mentioned formats, however it seems to happen most notably during AAC (PCM) with or without passthrough as far as I can tell. I have not observed it in DTS yet. As Puck says it is hard to reproduce. Please excuse my inexperience, I am trying my best.
I have used AAC-Videos with passthrough via HDMI with multiple devices (Blu-ray Player, Win7/Win10 Laptops) and I never encountered this phenomenon. As far as I understand, it is not very likely to be an issue of the AVR.
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