[MPlayer-dev-eng] [PATCH] audio filter volnorm2 - two-pass audio normalizer

[Rich Felker]

On Sat, Jul 30, 2005 at 01:44:05PM -0500, Zoltan Hidvegi wrote:
> Rich Felker wrote:
> > > Have you tried -a52drc option?
> > 
> > The default value is full drc I think.. Anything but default or zero
> > makes decoding unbearably slow, iirc.
> 
> What to do mean by making it unbearably slow?  It will add one pow
> call per AC3 sample, that's around 40 pow calls per second, but only
> for the samples where drc is indicated in the AC3 stream (the encoder
> must mark the portions of the steam that requires drc, and how much
> drc must be used).  I know you have a slow machine, but is it really
> that slow?

One call to pow plus one indirect function call per sample is at least
250 cycles per sample. That's 12 million cycles per second.. quite a
lot taken away from audio & video decoding (about 3% additional cpu
usage). It should be done internally (without the callback) and using
an efficient integer pow implementation.

BTW I haven't measured, but the above estimates are conservative IMO.

Rich