[Ffmpeg-devel] [PATCH] flacenc - lpc order search

Justin Ruggles jruggle
Sun Jul 16 06:27:12 CEST 2006


This is a pretty simple patch, but I thought should post it anyway
before committing since my svn account is still shiny and new.

It adds compression levels 6 to 12 which utilize the 2-level, 4-level,
8-level, and full search options for finding optimum LPC order.  The
*-level options basically just take an evenly-spaced subsampling of
orders between min_order and max_order.  This is simple, but it works
surprisingly well.

Combining level 12 with 10-pass Cholesky factorization makes for some
pretty good, albeit excruciatingly slow, results.  In the 1 test I cared
to wait long enough for, it gave a 0.3% compression ratio gain over
level 12 alone.  As far as compression time, it took 77.65s w/ level 12
vs. 1512.86s w/ cholesky 10-pass.

I'll take some time Sunday to do some more extensive benchmark comparisons.


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