[mythtv] [mythtv-commits] Ticket #1104: multi channel audio support

Mark Spieth mark at digivation.com.au
Fri Feb 1 22:10:01 UTC 2008

> Mark, how much work would it be to use ffmpeg's fourier transforms if
> fftw3 isn't available?
> Also, if we do use fftw3, we're going to need to check for it in
> ./configure and not use it if it isn't installed..

I havent analysed this yet. Note that mythmusic uses fftw3 already.
Hoever on a quick look at fft.c, fft-test.c it wouldnt be too hard.
However, lavc fft doesnt have a real-complex mode which only uses 1/2 the 
result (due to odd symmetry inherent in this mode of fft) so I suspect it 
will be slower. If this is important its doable within a few hours.
Things that need to change are the init/finalize, and filtering needs to be 
modified to use all 8k freq domain samples instead of 4k freq domain samples 
due to the symmetry not being redundant. scaling should be the same.

Still working on bug fixes. Ive figured out why swapping from 2 to 6 and 
back doesnt work. still working on a fix but lavc has a couple of changes to 
support it. hopefully an update this weekend for this.


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