[FFmpeg-devel] [PATCH] Simplify IMDCT in dca.c

[Benjamin Larsson]

Alexander E. Patrakov wrote:
> Michael Niedermayer wrote:
> 
>> Hi
>>
>> patch below replaces the duplicated IMDCT in dca.c by the standard one.
>> code is faster, simpler nicer, ....
>> yes the QMF of dca is a windowed IMDCT

Dca uses a cosine modulated pseudo QMF.

> 
> Yes, here it brings the time to decode a ripped CD down from 1m11s to 51s.
> Unfortunately, I could not test the SSE patch by David Conrad and compare.
> 
> Your change is not bit-exact WRT the previous version, but sounds right. The
> difference is of the form of 1-LSB-clicks (several random clicks per
> second - when amplified, sounds like a Geiger counter).
> 

When I changed from from double to floats in I also got lsb differences.
Non audible ones.

MvH
Benjamin Larsson