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# Auto Gain

Easy Effects Autogain is based on the library libebur128 which implements the EBU R 128 standard for loudness normalization. It changes the audio volume to a perceived loudness target that can be customized by the user.

Target
Loudness level.

Silence
Silence threshold. While the momentary loudness is below this value the autogain won't make any changes to the current gain being applied to the signal level.

Maximum History
Range of time taken into account for the calculation of loudness level and output gain.

Reference
The parameter used as reference to evaluate the output gain.

- Momentary - Measures the loudness of the past 400 milliseconds.
- Short-Term - Measures the loudness of the past 3 seconds.
- Integrated - Ideally it indicates how loud the content is on average. It measures the loudness on a long range of time, depending on the value set as Maximum History.
- Geometric Mean - Uses the geometric mean of all the above mentioned parameters, or two of them at user choosing.

Reset History
Resets the Autogain history related to chosen Reference.

Monitor Parameters
Autogain values shown as stats.

- Relative - Used to detect silence. Whenever the Momentary term is below a predetermined threshold, modifications to the output gain will be disabled.
- Loudness - The difference between its value and the target loudness determines the output gain.
- Range - Indicates how large is the dynamic range of the content played.
- Output Gain - The input signal is adjusted by this correction gain to bring its loudness to the target value.

## References

- Wikipedia EBU R 128
- EBU - Loudness Normalisation and Permitted Maximum Level of Audio Signals