Re: Newbie questions
Re: Newbie questions
- Subject: Re: Newbie questions
- From: Kevin Dixon <email@hidden>
- Date: Sat, 04 Apr 2009 23:36:51 -0700
A-B (left-right) transformations can be really useful for analyzing
mixing techniques, but I don't feel that they're extremely useful.
Here is a link to a plugin for Winamp I made that does A-B and A+B
transformations.
http://yano.wasteonline.net/software/ab/
The source code is available if you want to check it out. Its not
CoreAudio, but the fundamental math is the same.
If you want to get really crazy, you can make your A channel A-B and
your B channel B-A.
-Kevin
Brian Willoughby wrote:
It's a bit misleading when folks refer to this sort of thing as
'phase' - a more appropriate term would be 'polarity.' Only a pure
sine wave has a 180-degree phase shift when it's polarity is inverted,
but any changing waveform will obviously not have its features shifted
in phase at all, because they remain at the same precise time.
To get to your question, you basically subtract the two channels.
Using 'minus' is the same as reversing polarity of a channel.
Be warned that this effect produces a mono output from a stereo input,
and it does not cancel stereo reverb effects on the center channel
vocals. It will actually mix the reverb from both channels,
potentially making it louder. In other words, this is a very easy
effect, OUTPUT=LEFT-RIGHT, but you'll end up with a mono song with
ghostlike vocals remaining, unless there's no reverb or purely mono
reverb in the original.
It should be a fun first project, though.
Brian Willoughby
Sound Consulting
On Apr 4, 2009, at 11:55, James Cicenia wrote:
I need to make a voice remover. I have been looking around and
it seems that I can do a left / right channel phase operation to remove
the center channel vocals which is good enough for me.
Being absolutely new... I would appreciate any code, examples,
tutorials or things to read that could help me get started.
This will be for the iPhone.
thanks
James Cicenia
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