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  • C.R.Helmrich
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ABX fast switching artifacts
Reply #25
Think of the extreme case when comparing a signal with its polarity-inverted version (e.g. to test audibility of absolute phase).

That's not a good example, though - there, the short mute is, of course, unavoidable. (And the mixing ought to be symmetric around the mute.)

Well, the example is heading into the right direction. See below.
Quote
On a more general point, won't crossfading (regardless of the window used) always result in a transition where the correlation to A monotonically decreases, while the correlation to B monotonically increases? So why is correlation an issue? Of course there will be interaction between A and B, but I'm not clear how, on a per-critical-band basis, it would ever be damaging.

It can be damaging vor very tonal stationary encodings. I had this experience when blind-testing an AAC encoding of the Dolby pitch pipe item (si03 in the MPEG test set). AAC does relatively well at high bit rates, so you try to listen very carefully for the slightest amplitude modulations in the encodings. When cross-fading between the hidden reference and the encoding in the test, such modulations can occur because of partially destructive interference in some of the harmonics. I observed that some inexperienced listeners mistake these artifacts as codec artifacts and grade the affected stimulus (the one to which we fade) down. Sometimes, that's actually the hidden reference.

Don't know what's best for such an item, cross-fade or fade-out/fade-in. And that one particular test sample is the only one I know of where cross-fade modulations are a big issue.

Chris
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