Differences in response between PEAK compressor and RMS compressor

Hi Sivaram,

Can you please let me know which processor you are referring to? What software tools are you using?

Regards,
Anand Selvaraj.

Hi Anandh Selvaraj,

I am using ADAU1452 processor and Sigma studio 4.5 tool.

Hello sivaram,

I have attached a document I prepared a while back to explain some of the variables used in the dynamics cells and how they function. Most of our cells work using this same basic method.

You mentioned ratio so I just want to clarify that there is no single variable for the ratio, it is a table of gain factors which are calculated based on the graphics so the ratio is a result of the gain curve and not a specific number. But , your point in your question is that above a threshold a gain factor is applied.

So what is the difference between Peak and RMS? The only difference is how the level of the audio is obtained.

The peak is obvious that the level is reported out as the level of the signal peak. The MAX of the absolute value of the audio samples. Most of our peak compressors have an instantaneous attack time and then a hold time followed by a release time if the signal peak remains lower than the current saved level. So it is an envelope follower that follows the peak signal.

The RMS simply calculates the RMS value of the absolute value of the audio and uses that to determine the level of the audio.

Once the level is determined, the compressors both function that same in that they look up the level against the gain factor tables and computers the gain factor and applies it to the audio. The Gain factor is interpolated when it falls between two points of the table.

The RMS compressors all have an attack time and they will release just like the peak compressors do.

The sensed level will be different so they will not produce the same exact output unless you correct for the

There have been some bugs on some of the dynamics processors on some of the platforms. I am guessing you are having problems which is why you are asking the question. So if you could zip up and attack a project that demonstrates the problem you are having then I might be able to provide a better answer for you.

Thanks,

Dave T

PDF

Edited on Sept 3, 2020 to the updated document.

Dear DaveThib,

Thank you for the response,

As per the statement "The RMS simply calculates the RMS value of the absolute value of the audio" is there any formulae or theory to calculate the RMS levels.As we are trying to calculate the expected values of RMS Compressor theoretically,this will be helpful for us.

Kindly find the observations attached.

Kind Regards,

Sivaramakrishna

Dear Dave!

I too have this query ! Can you explain if thereis any formulae or theory to calculate the RMS levels