iTunes Sound Check album mode: what does this mean for $rg2sc?

I read and listened to Ian Shepherd's piece here discussing the apparent new iTunes ability to do both track and album gain leveling.

I just did a test rip in the latest iTunes and note that is still just creates a single iTunNORM tag field. I used axone.jar and did not see any new tag fields or header changes. So a few questions:

  1. How does iTunes do both album and track volume leveling with just a single tag field?
  2. If the content of the single iTunNORM tag field has been altered to contain both track and album gain info, does the function $rg2sc need to be tweaked to accommodate?
  3. Without any changes to $rg2sc, does its output still work as before (reflecting either track or album gain depending which RG value is used), or is this essentially broken with the latest versions of iTunes?

I don't have the tools to quantitatively evaluate what iTunes is doing or how it does what it does, so any insight appreciated.

What does this have to do with MP3tag? Could you please elaborate?

If iTunes knows what belongs to an album then it can calculate the role of each track. And then it can put the definition into one track and one field.

You read and listened to the link in my OP, right? $rg2sc is a function in Mp3tag, right? And this function is designed to work based on assumptions of how iTunes in the past used the output of $rg2sc when written to the iTunNORM or COMMENT iTunNORM tag field, right? So if iTunes has altered the content or use of iTunNORM or COMMENT iTunNORM, or if iTunes has created another way to do what these tag fields have done in the past so that iTunes can do both track and album-based volume leveling, then it makes sense to look at $rg2sc and see if it needs to be revised as well, right?

As you seem to know more than I do about this function: could you please show me where this is documented in the help?
You find the help in

You're obviously being passive aggressive about this, and it is undeserved and unprofessional. Google is your friend to find the many threads on this function in these fora, and one of the hits you'll get is the change log for Mp3tag v2.38 - and I'm sure you already know all of that. The lack of any help reference, of which you also already no doubt aware, is a red herring.

As you can see I joined this forum in 2009 - much later than v2.38 was released.
(see change log
[2006-12-12] NEW: function $rg2sc(x) which converts the ReplayGain value x to an iTunes SoundCheck value.)
So, thank you for sharing the source of your knowledge with me.
I could not find anything about this function in the other documentation. But you learn something new every day.

This post from Bob Katz could be an explanation. I myself have not tested if it's true.;#entry863377

Yes, I saw that post which describes "how" from a behavior perspective. But it doesn't describe "how" from the perspective of what needs to go in each of the ten hex segments of the iTunNORM tag field to accommodate the new method.

Given that Bob confirmed that iTunes has been changed in some way and that there is still just a single iTunNORM tag field, the simple conclusion is that $rg2sc seems broken, since the existing code for $rg2sc only writes track or album gain info and not both simultaneously. It may be fixable if iTunes has been changed such that the album and tag gains are stored in a reformatted iTunNORM tag field, but it may not be fixable if iTunes now uses a combo of iTunNORM and iTunes database info to do both album and track gain changes.

Determining how (from a tag field/database perspective) iTunes is exactly storing its new gain adjustments is the critical first step. If the new method depends solely on iTunNORM tag field content, then it should be fairly easy to revise $rg2sc code. But both of those steps are beyond my tools and expertise. I can only admire the problem!