Compressor Example

compressor.py

import numpy as np
from scipy.io import wavfile
from math import pow

def dB_to_ratio(dB):
    return pow(10, dB / 20)

def compress_audio(sample_rate, audio, threshold, ratio, attack_time, release_time):
    compressed_audio = np.zeros_like(audio, dtype=np.float32)
    gain_reduction = 0
    attack_coeff = np.exp(-1 / (sample_rate * attack_time))
    release_coeff = np.exp(-1 / (sample_rate * release_time))

    for i in range(len(audio)):
        # Threshold and Ratio for Compression
        if abs(audio[i]) > threshold:
            new_gr = 1.0 - (1.0 / ratio)
        else:
            new_gr = 0.0

        # Attack and Release
        if new_gr < gain_reduction:
            gain_reduction = attack_coeff * (gain_reduction - new_gr) + new_gr
        else:
            gain_reduction = release_coeff * (gain_reduction - new_gr) + new_gr

        # Apply compression
        compressed_audio[i] = audio[i] * (1.0 - gain_reduction)

    return compressed_audio

def apply_noisegate(audio, threshold):
    return np.where(abs(audio) < threshold, 0, audio)

def apply_gain(audio, gain_dB):
    gain_ratio = dB_to_ratio(gain_dB)
    return audio * gain_ratio

def apply_limiter(audio, threshold):
    return np.clip(audio, -threshold, threshold)

# Read WAV file
sample_rate, audio = wavfile.read("input.wav")
audio = np.float32(audio)

# Noise Gate
audio = apply_noisegate(audio, 1000)

# Compressor with Attack and Release
compressed_audio = compress_audio(
    sample_rate,
    audio,
    threshold=0.2 * np.max(np.abs(audio)),
    ratio=4,
    attack_time=0.001,
    release_time=0.1
)

# Gain in dB
compressed_audio = apply_gain(compressed_audio, 2)

# Limiter
final_audio = apply_limiter(compressed_audio, 0.9 * np.max(np.abs(audio)))

# Convert to int16 for saving
final_audio = np.int16(final_audio)

# Save output
wavfile.write("output.wav", sample_rate, final_audio)