[Krobar]

Thanks.  Two things there stood out to me.  Firstly, HDMI - ARC AV AMP.  Makes me wonder if you are connected PC-->TV-->AMP ?  ARC has caused me issues in the past so if you have it enabled, maybe try without it and see if that makes a difference.

Secondly, this bit is generic to all OS's and tells me that Kodi has seen the correct channel layout (we will have got it from the hint, which does contain the correct channel map).

xml:
2021-05-02 21:14:33.645 T:2032 INFO <general>: CDVDAudioCodecFFmpeg::GetChannelMap - FFmpeg reported 3 channels, but the layout contains 0 trying hints

2021-05-02 21:14:33.645 T:2032 INFO <general>: Creating audio stream (codec id: 65536, channels: 3, sample rate: 48000, no pass-through)

But, when WASAPI returns the channel layout we can use it gives us this.

xml:
2021-05-02 21:14:33.890 T:5748 DEBUG <general>: CActiveAESink::OpenSink - trying to open device WASAPI:default

2021-05-02 21:14:33.979 T:5748 INFO <general>: CAESinkWASAPI::InitializeExclusive: WASAPI Exclusive Mode Sink Initialized using: AE_FMT_S24NE4MSB, 48000, 4

2021-05-02 21:14:33.979 T:5748 DEBUG <general>: CActiveAESink::OpenSink - WASAPI Initialized:

2021-05-02 21:14:33.979 T:5748 DEBUG <general>: Output Device : default

2021-05-02 21:14:33.979 T:5748 DEBUG <general>: Sample Rate : 48000 2021-05-02 21:14:33.979 T:5748 DEBUG <general>: Sample Format : AE_FMT_S24NE4MSB

2021-05-02 21:14:33.979 T:5748 DEBUG <general>: Channel Count : 4 2021-05-02 21:14:33.979 T:5748 DEBUG <general>: Channel Layout: FL, FR, BL, BR

2021-05-02 21:14:33.979 T:5748 DEBUG <general>: Frames : 2400 2021-05-02 21:14:33.979 T:5748 DEBUG <general>: Frame Size : 16

Does directsound do the same thing?  I know that's not recommended for Win but might be worth a try.  I can try and add some more logging to the wasapi stuff and get another test build which might show more clearly if indeed kodi requests the right layout and it's the win driver giving us the incorrect one back but this is shooting in the dark a little as I can't test it!

Thank you for looking at this. The Amp name is confusing, no ARC involved, the brand is Arcam.

I did discover something interesting about this issue by setting various fixed channel configs with Wasapi audio. None of the odd channel numbers detect correctly:
2.1 outputs 4.0
3.0 outputs 4.0 (Same problem as this test file)
5.0 outputs 5.1
7.0 outputs 7.1

When using the "Optimal" setting mono PCM media is output as stereo and 6.1 PCM is output as 7.1 (Back left maps to center back).

The other things that is interesting is both 4.0 and 3.1 work correctly and the amp detects between them correctly. If I set a fixed 3.1 config then that clip plays correctly and upmixes correctly so not very user friendly but it is a good workaround. I suppose no one likes logic exceptions but 3.1 would be a much better output choice for a 3.0 signal than 4.0.

My hardware is Intel 8th gen I3 integrated graphics (UHD 630). Can anyone else using Windows with an AVR confirm what their results are for the odd fixed speaker configs above?

Directsound just seems to use stereo so seems to be a non starter. Edit: You were right looks like Directsound support far fewer channel configs than KS/WASAPI:
https://docs.microsoft.com/en-us/windows...nel_config

Does the fallback to hints change also effect the music player? I tried with some 4 channel Flac with the WAVE_FORMAT_EXTENSIBLE header set for 3.1 and 4.0 (SL/SR) and Kodi did not change the channel mapping.