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Raspberry Pi 5 hardware for music server
geoff2802:
Hi all,
Any ideas why MC is reporting 32-bit output? I’ve switched off / disabled every setting that looks like it might use the mixer / DSP.
Has anyone using MC on Linux found the same behaviour?
I would like to resolve and purchase licence.
Cheers, Geoff.
Awesome Donkey:
If you're referring to something like this and the output...
This is normal, as MC pads the bit-depth with zeroes on-the-fly to the max supported bit-depth the output device (DAC, receiver, etc.) reports that it supports. Take a 16-bit or 24-bit file and let's say your DAC/Receiver/etc. supports up to 32-bit, MC detects this and when you play back either type of file it basically just adds zeroes to the header during playback to make it appear to the DAC/Receiver/etc. as a 32-bit file, even though it's still a 16-bit or 24-bit file, if that makes sense. It's done this way for things like DSP and better overall compatibility. Do note it isn't dithering or resampling nor is it actually making any changes to the audio, it's just reporting it as 32-bit to the output, so nothing to worry about there. And before it's asked there's no way to disable the behaviour (it's this way on all platforms) as it's not harmful to the audio in any way.
geoff2802:
Thanks for the explanation Awesome - this is appreciated.
I’ve done some digging and the issue seems to be a mismatch between the audio channels in the flac files and ALSA’s channel assignments. When I use the speaker-test utility the test tones come from the correct speaker., so the Linux side of things seems fine in isolation When I play a flac file using MC, the channels are not right. I’m working on a change to the ALSA config to switch the channels around using a pcm route.
geoff2802:
Returning with some findings...
The symptoms when playing 6-channel FLAC content were as follows:
- No audible output from centre channel.
- Centre channel content appeared to be output to left surround speaker.
- Sub seemed to be receiving full range signal, not just LFE.
- No audible output from RS. Perhaps LFE was being sent to this speaker.
I understand Linux' channel assignments to be:
0 - FL
1 - FR
2 - SL
3 - SR
4 - Centre
5 - LFE
I'm aware that some other O/S's use different channel assignments.
Question: Does MC on Linux re-route channels in FLAC files when sending to PCM output? Or does it pass straight-through?
Based on my observations, I re-mapped the channels by configuring an ALSA PCM route as follows:
- Swapped channels 2 and 4. This should route the signal that was coming from SL to Centre and vice versa.
- Swapped channels 3 and 5. This should route the signal that was coming from SR to the Sub. (thinking that LFE signal would be inaudible on my surround speaker).
Results:
- Still no audio from Centre speaker. When I listen to the original source disc, I receive clear signal from this speaker.
- Some LFE audible from sub.
geoff2802:
Bad news: I couldn’t resolve the issue.
Good news: I bought a Mac Mini for this purpose.
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