Re: [LAU] Sanity check needed: Fons's Auto Wah on 64-bit system and CPU usage?

On Thursday 14 January 2010 02:38:04 Ken Restivo wrote:
> Turns out that on my Core2Duo, JACK RACK running Fons's auto-wah plugin
> sucks up 6% CPU even if there is no sound going through it.
>
> I asked Fons about it; he can't duplicate the problem since he doesn't have
> a 64-bit system. Hell, I can't even duplicate it on my 32-bit system; it's
> 64-bit dependent.
>
> I looked at the output with Bitmeter at Fons' suggestion, and it seems
> there are no denormals, inf's, or nans-- just a very small -230dB DC
> offset in the code (probably to avoid denormals).
>
> The CPU usage ramps up before any signal is fed into the plugin. It runs
> normally when there is signal, but then it keeps sucking up CPU
> afterwards. I'm feeding it from fluidsynth, and bitmeter says that it
> isn't sending anthing at all during silent moments.
>
> It doesn't run away to 99% CPU (or 50% on a Core2Duo), like it would if
> there were a denormal. But still, why is it using up CPU when there's no
> signal? That seems odd. And why only on my 64-bit machine? FWIW, the
> 64-bit and 32-bit machines I have are even running the same kernel and
> RT-patch versions (2.6.26.8-rt12).

Here is a shot:

Maybe the 64bit is better at calculation and -230dB are not yet good enough to
avoid denormals. What if you change that code to add a bit more offset?

Or use it in an ardour session for testing and try the different denormal modes
of ardour to see if one helps...

Have fun,

Arnold

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