Limiter
Added in v0.26.0
The Limiter, based on numpy-audio-limiter , is a straightforward audio transform that applies dynamic range compression.
It is capable of limiting the audio signal based on certain parameters.
- The threshold determines the audio level above which the limiter kicks in.
- The attack time is how quickly the limiter kicks in once the audio signal starts exceeding the threshold.
- The release time determines how quickly the limiter stops working after the signal drops below the threshold.
In audiomentations v0.35.0 and earlier, this transform introduced a delay in the signal, equivalent to a ~60% of the attack time. Starting from v0.36.0, the output is aligned with the input, i.e. no delay.
Note: In audiomentations v0.42.0, the dependency for this transform changed from cylimiter to numpy-audio-limiter , which is ~30% faster and easier to install for newer Python versions. The behavior stays the same, although there are minor numerical differences between the two.
Input-output example
In this example we apply the limiter with a threshold that is 10 dB lower than the signal peak
| Input sound | Transformed sound |
|---|---|
Usage examples
from audiomentations import Limiter
transform = Limiter(
min_threshold_db=-16.0,
max_threshold_db=-6.0,
threshold_mode="relative_to_signal_peak",
p=1.0,
)
augmented_sound = transform(my_waveform_ndarray, sample_rate=16000)
from audiomentations import Limiter
transform = Limiter(
min_threshold_db=-16.0,
max_threshold_db=-6.0,
threshold_mode="absolute",
p=1.0,
)
augmented_sound = transform(my_waveform_ndarray, sample_rate=16000)
Limiter API
min_threshold_db:float• unit: Decibel- Default:
-24.0. Minimum threshold max_threshold_db:float• unit: Decibel- Default:
-2.0. Maximum threshold min_attack:float• unit: seconds- Default:
0.0005. Minimum attack time max_attack:float• unit: seconds- Default:
0.025. Maximum attack time min_release:float• unit: seconds- Default:
0.05. Minimum release time max_release:float• unit: seconds- Default:
0.7. Maximum release time threshold_mode:str• choices:"relative_to_signal_peak","absolute"-
Default:
relative_to_signal_peak. Specifies the mode for determining the threshold."relative_to_signal_peak"means the threshold is relative to peak of the signal."absolute"means the threshold is relative to 0 dBFS, so it doesn't depend on the peak of the signal.
p:float• range: [0.0, 1.0]- Default:
0.5. The probability of applying this transform.