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Re: Looper crossfade advice

Whenever I need to "butt" two waveforms together in Sonar, I make sure that I hook them together at a zero crossing point, meaning a place where both waveforms cross the zero axis. That way I get perfectly silent merges. Is that a possibility for your app?
----- Original Message -----
Sent: Wednesday, September 28, 2011 8:23 AM
Subject: Looper crossfade advice


I've been making some changes to my iOS looper Loopy, to try to make loop transitions smoother, and I'm hoping to get some advice on crossfading loops.

Before, Loopy would record for the exact duration requested (the "clock" length), and then microfade to silence at either side of the boundary, over something like 128 frames.  It avoids any click at the boundary, but doesn't sound particularly smooth - in fact, it introduces a hole at the boundary.

So, now, my current strategy is to record for a fraction longer, both before and after the actual recording starts and ends, so that there's some extra audio (2048 frames, or 0.046s) at the start and end to overlap and crossfade (using an equal power x-fade).  So, prior to the crossfade, we have 2048 lead-in frames, then the loop recording, then 2048 lead-out frames.  Then I overlap those frames, like this: http://atastypixel.com/duyoq (diagram)

This sounds great, and super smooth, but a user was commenting that he can clearly hear the following downbeat after the recording of a loop.

It seems to me like this might be a necessary evil - we have to have extra audio to overlap, otherwise there's no other choice than to either have no crossfade, or to fade to silence, both of which are undesirable.

So, I was wondering - is there an alternative solution, to getting nice smooth crossfades at a loop boundary, without recording outside the loop?  What do hardware loopers do here?

Thanks heaps =)