Apple Music Sound Check Feature: Likely Audible Degradation or Not?

[1231rq32r1qw32r]

SoundCheck is a bit crude in that it has no provisions for anything other than track gain, but if memory serves there are some ReplayGain scanners that can basically write album gain into the SoundCheck fields instead. (It's basically the playback normalization equivalent of a single-button mouse.) Not sure how this would be handled on a streaming service though... check a few tracks from one album to find out.

This isn’t true. It scans and writes track data, but is smart enough to adjust on the fly when you listen to an album.

ReplayGain should really have done this.

 

[1231rq32r1qw32r]

Apple claims in its Digital Masters document that:

I.e., album gain.

The weird thing is, though, that it works as claimed on macOS. On iOS it has been broken for a long time now. I've tried two times to create a case with Apple about this issue. Strangely from iOS 14.6 (when lossless and spatial audio were introduced) it worked for a while. Now it's broken again... for AAC. For lossless it does work as advertised.

iOS version	AAC	Lossless
< 14.6		n/a
14.6 - 14.8
15.0	?
15.1
15.2

To make Sound Check work, Apple should fix this bug. But I would also like an option where we can set the normalisation level. Now it's something around -16dB, but I'd like an option to set it to -23dB (just as it is possible in Spotify) to prevent some classical recordings to get a positive gain with the risk the limiter kicks in...

If you want custom loudness for SoundCheck, there are tools to achieve it. It’s a royal pain in the ass tho.

Also, foobar can write soundcheck data with custom parameters too.

 

[kongwee]

Just ignoring when you switch track and the volume forcefully trim by the app. Like orchestra track to EDM.

 

[srrxr71]

I didn’t realize it does positive gain also. For classical music wouldn’t it have scanned the whole track and kept the entire track within limits?

 

[lars1950]

follows:

mtomh:
I have the same question. Did you get a conclusive answer?

 

[tmtomh]

mtomh:
I have the same question. Did you get a conclusive answer?

Earlier in the thread, @Vincent Kars said that SoundCheck does use 32-bit float.