What is limiter error?

We introduce AI Mastering's "limiter error".

What is "limiter error"?

"Limiter error" is the error of sound caused by AI Mastering's limiting process .

Generally, if the sound pressure is raised too much with the limiter, the sound will be distorted, but the limiter error quantitatively expresses that distortion. It is designed based on psychoacoustics so that it approaches the human sense as possible. The unit is dB. If the limiter error is 1 dB or less, you should not be able to hear the difference.

The figure is simplified, but in fact it calculates it in a slightly more complicated way.

Cause of occurrence of "limiter error"

The cause of the limiter error is that the waveform is distorted as a result of attempting to bring the sound pressure closer to the target sound pressure while limiting the peak of the waveform to less than Ceiling by limiting processing.

There are some sounds that are distorting and distortion-proof with limiting. Whether distortion is easy depends on the limiter, but in the case of AI Mastering, percussion instruments are hard to distort, bass, close to sine waves, sustained sounds are easy to distort .

Tips for not generating "limiter error"

Decrease target sound pressure

Lowering the target sound pressure makes it easier to reduce the limiter error. This is the best when you can lower the sound pressure.

"Ceiling mode" is set to "peak"

In AI Mastering's custom mastering, you can choose whether to limit based on True Peak or normal peak using the Ceiling Mode option.

Because it suppresses the peak more conservatively based on True Peak, Ceiling goes down, and limiter error tends to occur.

By setting "Ceiling mode" to "Peak" , limiter error can be reduced. Instead, it is more likely to be distorted by lossy compression.

Small base peak

The bass is a low-pitched sustained sound close to the sine wave, so it's easy to distort at the limiter.

Although it is not limited to AI Mastering, if you use an amp simulator etc. to increase the overtones of the bass , you can reduce the peak while maintaining the audible volume. Instead, the sound quality changes.

I do not care that the "limiter error" is large

There are musically acceptable and unacceptable cases in which "limiter error" occurs.

For example, the sound of the bass is temporarily too large and the peak pops out, so if you lower the sound of the bass overall, "limiter error" will occur but I think that it is musically acceptable.

On the other hand, I think that it is not musically acceptable in the case of distorting it by forcibly suppressing the base peak in the same situation.

"If there is no limiter error occurred, there is no problem" is established (at least though it is designed to be established), "There is a problem if a limiter error has occurred" is not established .

So, it is also a hand that you do not mind that "limiter error" is big if you listen with your ears and have no problem.

Improvement plan "Limiter error spectrogram"

"A limiter error" displayed by AI Mastering is the average of the entire sound source. In reality, the local "limiter error" differs for each time and band.
If there is something like a spectrogram of "limiter error", you can see at which time and within what band "limiter error" is occurring, you can easily identify the cause.

It is under consideration.

Summary

We introduced about AI Mastering's "limiter error".