audio-batch-speedup

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A Rust library and command-line tool for batch processing and speeding up audio files using ffmpeg.

This crate was initially designed for visual novel audio speedup, as visual novels typically use a large number of OGG files for their audio system. It has since been extended to support a wider range of audio formats.

Features

• Parallel processing of multiple audio files recursively, maximizing speed by utilizing multiple CPU cores.
• Configurable speed adjustment.
• Support for multiple audio formats.
• Format detection: Prioritizes detecting audio format from file content (magic bytes) and falls back to file extension if content detection is not possible.

Usage

Command-line (bin) Usage

First, install the package. You can install it from Release manually or use cargo-binstall:

cargo binstall audio-batch-speedup

Then, run the executable:

abs --input /path/to/your/audio/folder --speed 1.5 --formats ogg,mp3     # speed up all OGG and MP3 files in /path/to/your/audio/folder by 1.5x

Arguments:

• -i, --input <INPUT>: Path to the folder containing audio files.
• -s, --speed <SPEED>: Audio speed multiplier (e.g., 1.5 for 1.5x speed).
• -f, --formats <FORMATS>: Comma-separated list of audio formats to process (e.g., ogg,mp3,wav). Use all to process all supported formats. Supported formats: ogg, mp3, wav, flac, aac, opus, alac, wma. Default: all.

Library (lib) Usage

Add audio-batch-speedup to your Cargo.toml:

[dependencies]

audio-batch-speedup = "0.1" # Use the latest version

Then, in your Rust code:

use std::path::Path;
use audio_batch_speedup::{process_audio_files, AudioFormat};

fn main() -> std::io::Result<()> {
    let folder = Path::new("path/to/your/audio/files");
    let speed = 1.5;
    // Process OGG and MP3 files
    process_audio_files(folder, speed, AudioFormat::OGG | AudioFormat::MP3)?;

    // Process all supported audio files
    process_audio_files(folder, speed, AudioFormat::ALL)?;

    Ok(())
}

Encoding

Speeding up requires decoding and re-encoding the audio stream. To avoid the quality loss of ffmpeg's default per-container encoder settings, each format is re-encoded explicitly:

For lossy formats, the output bitrate is capped at the source bitrate (detected via ffprobe) so that a speedup never inflates the file size; files with a source bitrate at or above the defaults use the settings above. If ffprobe is unavailable, the default settings are used for all files.

This requires an ffmpeg build with the libmp3lame, libvorbis, and libopus encoders enabled (most full builds include them).

Requirements

• FFmpeg must be installed and available in the system PATH.