[flac-dev] [PATCH] New apodization functions

Martijn van Beurden mvanb1 at gmail.com
Sun Sep 21 06:39:12 PDT 2014


> If I understand this correctly, these new apodization functions only
> affect compression and that files compressed with these new functions
> will still decode correctly with older versions of the FLAC decoder.
> Is that right?

Yes, that is correct. These functions are used to window the 
audiodata, but only for the predictor stage. What these new 
function enable, practically speaking, is using only part of the 
signal to generate a predictor. My theory is that this helps 
because short transients introduce noise into the predictor. The 
predictor becomes very good at prediciting one part of the 
signal, instead of mediocre for the whole block.

For more information on the whole window-thing, it might be a 
good idea to see this hydrogenaudio-post by Josh himself: 

One thing to note is that this patch only affects the encoder 
stage that evaluates various possible predictors, not the actual 
coding stage.

This patch only add the new windows to the codebase. My 
follow-up e-mail (Retuning compression levels) suggests one 
possible retuning of the compression levels 6, 7 and 8 that make 
use of these new functions.

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