[FFmpeg-devel] [PATCH] Removal of the "noidea" buffer in dca.c

Alexander E. Patrakov patrakov
Mon Sep 8 12:48:48 CEST 2008


The attached patch rewrites the dca.c file in order to remove the
not-very-understandable buffer. I think that the new code is easier to
understand. Previously, the 512-element history buffer stored the DCT
of the input subband samples. Now it serves directly as a PCM mix
buffer. Deobfuscation of prCoeff (i.e., flipping the sign in some
places) is not done, because the code is shorter this way.

The output is not bit-exact to the previous version, but the
differences are only in the least-significant bit.

Please don't apply this patch, just use it as a reference, because it
slows the things down on this Celeron 1200.

before: 0m2.005s
after: 0m2.295s

(on a 2m49.86s 256kbps stereo file)

Alexander E. Patrakov
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