Problem with Threshold Limiter

Hi Christian,

The Limiter in the SigmaStudio library is actually an RMS limiter. It does not use true RMS detection, which is very expensive computationally, but it uses an approximation of RMS. Since you are using a sine tone, the RMS level of the signal is actually 3 dB less than the peak of the signal. This means that you'll need to apply +3 dB of gain to the signal in order for the RMS level to exceed the 0 dB threshold you have set on the limiter. The approximation of RMS is not exact, so this is why there's about a dB discrepancy.

In my attached example, I instead used a Square wave as the source signal, because for a square wave, the RMS level is equal to the peak level. When I take my 0 dB square wave and apply a +3 dB gain, I now have a signal with an RMS level of +3 dB. On the output of the limiter you can see the three DSP readback cells.

OutputPeakLevel = 0.9999, because the limiter is keeping the square wave at +/- 0 dBFS peak.

LimiterActive = 1, because the limiter is turned on.

GainApplied = 0.707 ( = - 3 dB ), because the + 3 dB square wave needs - 3 dB of gain to go back to unity.

I would like to implement a peak limiter in SigmaStudio with look-ahead delay and intelligent release. Hopefully, we'll be able to include that in an upcoming SigmaStudio version.

Thanks!

BrettG wrote:

I would like to implement a peak limiter in SigmaStudio with look-ahead delay and intelligent release. Hopefully, we'll be able to include that in an upcoming SigmaStudio version.

Any progress on that?

Edit: Lookahead limiter example is here. For mono input, you can use the "Peak (no gain)" block and then Add Algorithm "Mono Peak (no gain)". It doesn't say "external detect" anywhere, but this mono block has external detect, and can use a delayed signal to the main input to implement lookahead.

Unfortunately this has not been integrated into a single block yet, but it can be implemented manually, following the tutorial that you just posted.