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

Daniel Kristjansson danielk at cuymedia.net
Fri Feb 1 22:18:05 UTC 2008

On Sat, 2008-02-02 at 09:10 +1100, Mark Spieth wrote:
> > 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.

I think it's important because this still adds another lib requirement.
For MythMusic it isn't a required lib. We should still use fftw3 when
it's available. It really is the fastest free FFT library out there.

> 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.

Cool, finding the cause is usually more than half the work.

Did you figure out the problem with DVB radio too?

-- Daniel

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