SigmaDSP Standard RMS Compressor Algorithm Reference

Currently using the standard independent RMS module to implement Dynamic Range Compressor/Limiter

Now, I will describe the specific situation in detail

The transfer function of the current compressor parameters, including threshold, ratio, and knee (knee=1), has been verified to match the calculation results of the sigmastudio software, as shown in the figure

compressor transfer function： register value = pow(10, (Input <= Threshold ? 0 : ((1/Ratio - 1)*(Input-Threshold))/20))

attack time transfer function： float coeff = (1.000f - expf(-1.000f / (time_ms * (sample_rate / 1000.000f)))) * 2.000f;

release time transfer function：float coeff = 0.0905f / (sample_rate * (time_ms/1000.0f));

Currently, we still need to implement soft knee (knee > 1), and we haven't derived the formula for this yet. Could you please provide relevant information or a formula? I think the soft knee curve looks more like a double tangent curve, and the larger the knee, the farther it is from the inflection point.

Thanks & BR

Thread Notes
Harishgowtham - Moved from Processors and DSP to SigmaDSP Processors & SigmaStudio Dev. Tool. Post date updated from Wednesday, July 30, 2025 7:07 AM UTC to Thursday, July 31, 2025 5:31 AM UTC to reflect the move.

Harishgowtham - Moved from Processors and DSP to SigmaDSP Processors & SigmaStudio Dev. Tool. Post date updated from Thursday, July 31, 2025 5:31 AM UTC to Thursday, July 31, 2025 5:31 AM UTC to reflect the move.

Audio Signal Processors

adau1452

software

SigmaDSP Standard RMS Compressor Algorithm Reference

SigmaDSP Audio Processors

SigmaStudio 4.5

Show More