Does "Mastered for iTunes" matter to music? Ars puts it to t, Article about Apples "Mastered for iTunes" program Options

[knutinh]

Thought this might be interesting, and did not find it mentioned in other posts:
http://arstechnica.com/apple/news/2012/04/...-the-test.ars/1

[stephan_g]

Comments >> article.

The article illustrates nicely that the underlying motivation for "Mastered for iTunes" is not generally understood. The comment by itsbenaltogether sums up the central points pretty well:

[...] All this article is saying is that it is possible to master a record in a way that reduces artifacts due to AAC compression. This doesn't sound that outrageous to me and the advice Apple is giving people isn't exactly rocket science either. If AAC compression can cause clipping, it's a no brainer to reduce the levels before compression. To do this most effectively, it helps to have the best dynamic range signal available. This all sounds straightforward to me.

Add the point that heavy dynamic compression tends to introduce more high-frequency content which, being harder to encode, either gives higher data rates or reduces overall quality, and you've got the gist. Not rocket science to him or to me or anyone else with some kind of signal processing background, but to the average mastering engineer it apparently is. This article could have done something about this, but as-is it's just yet another missed opportunity.

This post has been edited by stephan_g: Apr 30 2012, 13:04

[knutinh]

...

[...] If AAC compression can cause clipping, it's a no brainer to reduce the levels before compression. To do this most effectively, it helps to have the best dynamic range signal available. This all sounds straightforward to me.

...

Would it not be simple to automate this in the encoder implementation?

Add the point that heavy dynamic compression tends to introduce more high-frequency content which, being harder to encode, either gives higher data rates or reduces overall quality, and you've got the gist.

What would the consequence be of coding a highly-dynamic waveform, and transmitting the compression parameters as a small meta-data field, for doing heavy compression after decoder instead?

-k

[DonP]

What would the consequence be of coding a highly-dynamic waveform, and transmitting the compression parameters as a small meta-data field, for doing heavy compression after decoder instead?
-k

You could hack that data and skip or reduce the compression.

I have no inside knowledge of how these guys operate, but I suspect the parameters are not always constant through a whole track, so that field may have to be in each frame or otherwise time coded rather than just one time up front.

This post has been edited by DonP: Apr 30 2012, 14:29

[knutinh]

You could hack that data and skip or reduce the compression.

True. Why should an artist or mastering studio fear that their paying customers found ways to reduce the compression applied to their tracks, any more than how they are able to change the linear frequency response by applying eq?

I have no inside knowledge of how these guys operate, but I suspect the parameters are not always constant through a whole track, so that field may have to be in each frame or otherwise time coded rather than just one time up front.

Sure. But even if one allowed 3-5 bands of time-variant gains, I would suspect that they could be easily compressed (signal-dependant and correlated in time/frequency).

If they want complete flexibility (to use e.g. 1960s tube compressors), I could live with Apple having access to both pre-processed and post-processed versions, using some fancy compare/encode algorithm to transmit only clean source + mastering-process information.

-k