[PROBLEM] Volume Normalisation bug

[Sehnsucht]

I'm using v7.3 on a Pi Zero W and the Apple USB -> 3.5mm dongle.  It's all working great.

Until I enable Volume normalization on the mpd settings page.  This works but at the start of a track where there's little/no audio for a few seconds there's a very loud buzzing noise.  I suspect what's happening is that the normalisation isn't skipping ahead and just blindly amplifies the audio to the max and adjusts it back down when the music turns up.  When I rewind to the start of the track it must be happy with the boost it's applying and doesn't repeat the process with the buzzing.  The same with jumping between tracks - once it's sorted out this hiccup it doesn't repeat the problem, until I press stop, then it will come back again, like it's resetting the boost level.

Is there some better way of doing this, such as seeking forward looking for the loudest point in the song before playing any of it? Perhaps seeking a 90 minute track might take a bit long so limiting it to a few seconds/minutes might be enough.

I'm using the EU dongle which is known for its quiet maximum output level (which is why i'm using normalization in the first place) - when I was fiddling with alsa (back before I started using moOde) I was using an equalizer and got what I think was a very similar sound when I tried to boost the level that way so it's possible the problem is a combination of not knowing how much to boost, and the dongle not being especially clean when pushed?   The buzzing noise is identical regardless of which music I play so it's not part of the .flacs themselves.

[Tim Curtis]

Try switching to mixer type Hardware in MPD Config.

[Sehnsucht]

Try switching to mixer type Hardware in MPD Config.

Yep, that fixed it, thanks!

Still has the artefacts at the start where songs which build up slowly have the initial really quiet few seconds played as loud as the loud parts of the track, like a compressor would do.  Once it's got to the loud parts of the song and you restart the track it plays those parts at a more correct relative volume.  Is there some "better" way of handling this?   If doing a quick peak detection before the first track plays (other tracks are likely to be around the same max volume, on average?) isn't on, then perhaps not fully normalizing the audio in the first few seconds...assume that a lot of tracks fade in or build up from the start, and tracks which start off a full volume aren't going to suffer because they're already loud?     This isn't a huge problem, obviously, but if I can work around the problem by quickly dragging the progress bar around a few tracks of that album before returning to the start of the first track then presumably moOde could do that automatically too?

[Tim Curtis]

There haven't been any recent trouble reports in our Forum regarding MPD volume normalization nor any issues that I could find in the MPD repo https://github.com/MusicPlayerDaemon/MPD/issues

Maybe its a problem with the files or some issue with the device?

[Sehnsucht]

There haven't been any recent trouble reports in our Forum regarding MPD volume normalization nor any issues that I could find in the MPD repo https://github.com/MusicPlayerDaemon/MPD/issues

Maybe its a problem with the files or some issue with the device?

It's not the files.  I suppose it could be the device.  But isn't it more likely to be just what I already suggested about how the normalizing works?  Without scanning the whole track looking for peaks so that it can determine that it needs to multiply the amplitude by, say, 1.2 it instead says "well, this is pretty quiet so I'll scale it by 10" then as the audio in the track gets louder it reduces that scaling down bit by bit until it arrives at the the peak and ends up with 1.2.  And it keeps this value for subsequent tracks which is why you don't get this artefact at the start of every track on an album. (You would get it at the start of, say track 2, if that was the first track you played - part of the proof that it's not the files).

[Tim Curtis]

I don't know what algorithm MPD uses to do volume normalization. I'd suggest asking the maintainer about it by posting an issue. The mpd.conf option is named "volume_normalization" and the help for it is in the example mpd.conf file in the repo https://github.com/MusicPlayerDaemon/MPD...nf.example