[Ffmpeg-cvslog] r5747 - trunk/libavcodec/flacenc.c

Michael Niedermayer michaelni
Sat Jul 15 12:06:09 CEST 2006


On Fri, Jul 14, 2006 at 08:42:10PM -0400, Justin Ruggles wrote:
> I do have a question.  The Levinson-Durbin recursion as implemented
> essentially calculates all LPC coefficients for each order from 1 to
> max_order.  Can Cholesky factorization do the same?

this is a good question :)
i think the awnser is no, the problem is that while for Levinson-Durbin
recursion we assume a infinite block length and in that case the resulting
autocorrelation matrix will not change depending on the number of LPC
coefficients, while the actual autocorrelation matrix will change
following example shows why:

for order 3
audio input:            a b c d e f g h
samples stored as is:   a b c
samples predicted   :         d e f g h

for order 2
audio input:            a b c d e f g h
samples stored as is:   a b
samples predicted   :       c d e f g h

the difference is minor of course but so is the difference between
Levinson-Durbin and Cholesky

if we ignore this, then yes cholesky should be able to output shorter
predictors too

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is

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