[MPlayer-dev-eng] Audio plugins

[Anders Johansson]

Hi,

> On Mon, 18 Feb 2002, Anders Johansson wrote:
> 
> > There is now a generic FIR filter implemented in MMX and C which could
> > be used to finish the Dolby Surround decoder (Stephen Davies, you
> > wrote it do you want to do it or do you want me to do it?) and build
> > an EQ.
> 
> Hi,
> 
> I would be happy and interested to do the integration - though it will
> probably be the weekend before I'll have time to look at it seeing I'm
> away for work this week.
> 
> You are of course welcome to have a go, though I'd appreciate a patch
> before you commit changes.

No worries, I'll have plenty to do especially if Gabucino accepts my
offer to help him with the docu ;), just wanted wanted to make sure
you were still around.

> If your filter fast enough to run enough coefficients to do say a 120Hz
> low-pass to generate an LFE channel?

It should be, the MMX code can process one sample in less than 10 clock 
cycles, so 1% cpu on a 1GHz machine should give you a 1M tap FIR :).  
My guess is that you will get a good result with 32-64 taps. Have a
look in fir.h, you should use UPDATE_QUE() and firn(), see pl_resample
for usage and remember to make:

(L = 2^k) > (the length of your fir filter).

Perhaps UPDATE_QUE should be an inline function instead, and not
depending on #define L, what do you think?

> For the surround decoder I still have design ideas etc for some logic
> steering, but haven't done much implementation so far...

:)
 
> Steve

//Anders