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Hear what you don't hear...?
MiskyWhixer
post Jan 19 2003, 13:22
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I played around with Cool Edit a little bit.
I ripped a song with EAC to WAV and encode it to MPC Std, Xtr, and Ins (and MP3 APS)
Then I decode all the files back to WAV-File. Now I load the original WAV with CE and "Mix-Paste" (both channels inverted, Overlap Mix) with a decoded file. The result is a quiet wave sounds like... hmmm... can't explain in english ;o)
The higher the quality of the mpc file, the quieter was the difference. The MP3 APS wave had roughly the same loudness as the MPC Xtreme wave.

Am I right that this "difference wave" is the "lossy" part of the original wave after encoding?
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Gecko
post Jan 12 2004, 00:42
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Microsoft followed the same line of argument with WMA7. They observed the difference between WMA vs. original and MP3 vs. original and found that WMA sounded better because the difference to the original was smaller.

Unfortunately WMA7 sounds worse than MP3 in most cases.

A codec which doesn't throw away the inaudible stuff, which leads to an increase in difference, can be considered inefficient. You want a psychoaccoustic codec to throw away as much as possible while still sounding the same.

edit: Thasp, please also be aware that some codecs introduce a small delay when you encode and then decode again so you have to align the waves carefully before subtracting them from another. You can use Cool Edit Pro's multi track features to accomplish this. There is also another way of inverting one of the wavs without using the clipboard: goto effects>amplitude>channel mixer and set it up like this:
New Left Channel: L 100 / R 0
New Right Channel: L 0 / R 100
and tick "invert" on both instances.

This post has been edited by Gecko: Jan 12 2004, 00:49
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