Re: [linux-audio-dev] Paper on dynamic range compression

From: Steve Harris <S.W.Harris@email-addr-hidden>
Date: Wed Oct 18 2006 - 13:57:52 EEST

On Wed, Oct 18, 2006 at 11:12:32 +0100, Dan Mills wrote:
>
> --- Steve Harris <S.W.Harris@email-addr-hidden> wrote:
>
> > > But that puts potentially expensive gain
> > > calculations into the fast sr code, also I was
> rather planning
> > > on using the impulse used for the upsampler to
> > >provide the band limiting for free.
> >
> > the gain calculations are relativly cheap, its
> > converting those gain
> > levels back into a gain coefficient on the output
> > that's expensive (from
> > what I remember).
>
> But all that can still be done at 44.1/48, it is only
> the final sample multiplication that needs its inputs
> band limited and thus potentially needs the upsampler.

It's not that simple. The gain coefficient is not calculated for every
sample.

> > I dont think a streaming resampler is more
> > challenging than a correct one
> > that runs on buffers. You just have to preserve
> > state with every call,
> > rather than at the buffer boundaries.
>
> But that breaks the ability to use the vectorisation
> capability of modern compilers and besides the call
> and return overhead will end up costing as much as the
> convolution!

The vectorisation point is right, but the call and return is taken care of
by inlining in modern compilers, it's quite cheap.

- Steve
Received on Wed Oct 18 16:15:05 2006

This archive was generated by hypermail 2.1.8 : Wed Oct 18 2006 - 16:15:06 EEST