Seems I've been throwing you several red-herring. But I think I made
some progress last night.

According to http://docs.info.apple.com/article.html?artnum=61655 -
depending on the file format, iTunes sometimes stores the normalisation
information in the XML and sometimes directly in the file tags.  

Of course, Apple being apple they couldn't use the RVAD tag so they
have chosen to create a new iTunNORM tag which many editors can't
display (hence I was unaware I even had files that had been
normalised).

The code to convert iTunes Sound Check information into a dB value
seems to be stored in SlimServer\Slim\Utils\SoundCheck.pm. You can see
how it arrives at the dB values there.

Querying my SlimServer db I was able, to my surprise, to see that lots
of my tracks had Replay Gain data.

Using the Extended Tag mode of Mp3Tag (http://www.mp3tag.de/en/) -
which also supports AAC files - I was able to see (and delete) the
itunNORM tag on a few files.

This had the effect within SlimServer of instantly (no need to rescan)
deleting the "volume adjustment" setting on the info page and the
REPLAYGAIN values from the database. iTunes also seems to still play
the files fine.

So, where do we go from here...

I can't see any way to access the iTunNorm tag via the iTunes SDK.
Looks like they don't publish it as a property you can read or set.

The Mp3Tag tool seems to support some sort of scripting interface (they
call them actions). There is a thread
(http://www.anytag.de/forums/lofiversion/index.php/t3500.html) on their
forums about scripting deletion of this data. I'm going to look into
this route to strip these tags.

As to your suggestions...

I agree - there should be a server option to switch on or off the
application of replay gain data. Since it was your idea I suggest you
raise a feature request at http://bugs.slimdevices.com

It's also not clear to me what happens if you have manual iTunes
slider, Sound Check and some other system (e.g. AACgain) adjustments on
a file. Which takes priority? Could get messy.

Cheers,

BarCar.


-- 
barcar
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