Audio FX processing power... when they're not running ?!?

Hi all on this forum,

I'm a sonar X1 user since a few month and since that time I experience a strange behaviour of the DAW : the audio FXs I put in my project use more processing power when they have... nothing to process ! Is this normal ?

Exemple : When I do a song that uses several tracks (let's say so 20) and then suddenly gets into a more quiet part where only 2-3 tracks play, the CPU usage gets up and sometimes even causes dropouts, whereas it works fine while all the audio FXs are processing data (to stay in my example, when all the 20 tracks play together).

Muting channels does not solve the problems... it rather increases it !

Also some projects run out of processing power... even before I hit the play button !

Freezing tracks does not help neither as the total amount of processing power my softsynths alone (with no extra audio FX or prochannel stuff on them) do not pump more than 10% of my machines processing power.

Bypassing the audio FXs (by clicking on the "FX" button in the upper bar, in the mixing module) reduces the processing power use from dropout (or near dropout) to almost nothing (10-15% max). But of course, I have no FX on my tracks when using this...

In every other system I have seen, when less tracks are to be treated by Audio FXs, or when the song isn't playing at all, the FXs do not pump processing power... is it possible to configure Sonar to behave that way ?

If yes, How ?

Thanks in advance for your replies,

Best regards, Philippe.

Hi Bvideo,

Thanks for your answer and thanks for explaining me what floating point "denormal" or "subnormal" is.

OK, some of the FXs I use :

Kjaerhus plugins (chorus, limiter,...)
TAL plugins (filter, reverb...)
or any other plug actually.

But they don't cause the problem.

Actually, I tested my biggest project with all the Prochannel (I run X1 producer edit) features off but all other audio plugins on : those others pump at max 20% of the processing power.

Conclusion : my heavy use (low and hicut on almost every channel + tube sat sometimes + compression sometimes) of prochannel features is what does the bad thing...

Also note that every time I encountered that problem (read : in every of my projects) it happened when I tweaked too many prochannels...

Anyone can help me ?

Yes, unfortunately it is "normal". Plugins generally don't stop working when they have no input, and indeed many will chew up CPU when the project isn't even playing! (It's the plugin's fault, not the host DAW's)

You may be seeing an issue which occurs with very small signals, signals we would classify as "silence" from an auditory perspective but are still considered valid data by the software. The CPU (actually the FPU) switches to a special high-resolution mode when dealing with very small numbers, a mode that's more CPU-intensive. Some plugins add dither noise to "silence" in order to avoid triggering this mode.

SONAR does have an option for substituting very low-level semi-silence with zeroes, DC values or noise. Open your aud.ini file and look for a variable named "ZeroFillMethod" in the [AUD] section. If it's not there, add it like this:
        ZeroFillMethod=0

Use 0 to fill silence with zeroes, or 4 to fill silence with low-level noise.