fast-mp3-augment

A fast Python library for MP3 encoder + decoder data augmentation. Made for integration with audiomentations. Intentionally applying audio degradation by lossy compression help machine learning models learn to deal with audio that gets streamed from various internet services, which is commonly lossy/compressed.

Installation

$ pip install fast-mp3-augment

Code example

import numpy as np

import fast_mp3_augment

audio = np.random.uniform(-1, 1, (2, 2 * 48000)).astype("float32")
augmented_audio = fast_mp3_augment.compress_roundtrip(
    audio, sample_rate=48000, bitrate_kbps=64, preserve_delay=False, quality=7
)

Features

• The output is perfectly aligned (no delay/offset and padding) with the input by default, but this trimming behavior can be disabled (with preserve_delay=True)
• Supports mono and stereo
• Supports standard MP3 bitrates (8-320 kbps)
• Supports common sample rates (8-48 kHz)
• Inputs and outputs float32 numpy array
• Adjustable quality parameter for various tradeoffs between speed and audio quality

Performance

This library is largely developed with Rust under the hood (via pyo3 & maturin), and applies a few nice little tricks for achieving speedy execution (which is important during large-scale audio ML training!), such as:

• Fast numpy array interop between Python and rust
• In-memory computations (no disk I/O)
• SIMD-optimized max abs calculation (for avoiding clipping distortion)
• Pipelining/streaming (LAME encoder and minimp3 decoder in separate threads)

A quick performance benchmark (based on demo.py in audiomentations), which augmented 3 short (~7-9 sec) audio snippets (2 mono, 1 stereo) on a laptop with i7-13700HX and a 2 TB Samsung PM9A1 NVMe shows that fast-mp3-augment is superior when it comes to speed:

Changelog

[0.2.0] - 2025-12-15

• Bump min Python version to 3.10
• Officially add support for Python 3.14
• Make builds slightly slimmer

For the complete changelog, go to CHANGELOG.md

Development setup

• conda create --name fast-mp3-augment python=3.11
• conda activate fast-mp3-augment
• pip install -r dev_requirements.txt
• maturin develop
• pytest

LAME note

fast_mp3_augment statically links libmp3lame 3.100 (LGPL-2.1-or-later). Full source is available here. To rebuild the wheel against a modified LAME, see mp3lame-sys