What is ALAC?
ALAC (Apple Lossless Audio Codec) is a lossless audio codec developed by Apple Inc. and introduced in 2004 as part of iTunes. Initially proprietary, Apple made the codec open source in 2011. ALAC provides perfect audio reproduction while achieving significant file size reduction, making it the preferred lossless format in the Apple ecosystem.
Key Features
ALAC offers several distinct advantages:
- Lossless compression: Preserves 100% of the original audio data
- Native Apple support: Built into iOS, macOS, iTunes, and Apple Music
- Efficient compression: Typically reduces file size by 40-60%
- Low computational requirements: Designed for efficient decoding on mobile devices
- MP4 container compatibility: Uses standard .m4a container format
When to Use ALAC
ALAC is particularly well-suited for:
- Apple ecosystem users (iPhone, iPad, Mac, HomePod)
- iTunes library management and Apple Music integration
- Lossless audio playback on iOS devices
- Creating archival copies of music while staying within Apple's ecosystem
- High-resolution audio playback on Apple devices
Technical Details
ALAC supports sample rates up to 384 kHz and bit depths up to 32 bits. It can handle multichannel audio with up to 8 channels. Although technically the format would use the .alac extension, in practice ALAC files are stored in an MP4 container with the .m4a extension. The official MIME type is "audio/alac" though "audio/mp4" is often used when contained in an MP4/M4A file.
Compression Efficiency
While ALAC doesn't compress audio quite as efficiently as some other lossless codecs like FLAC:
- Typical compression ratio: 40-60% reduction from uncompressed audio
- CD-quality album size: Approximately 300-450 MB for a full album
- Decode efficiency: Optimized for lower CPU usage, beneficial for battery life
ALAC vs FLAC
The primary differences between ALAC and FLAC:
- Ecosystem: ALAC has native support in Apple products; FLAC has broader third-party support
- Compression efficiency: FLAC typically achieves slightly better compression
- Metadata support: FLAC has more extensive metadata capabilities
- Container format: ALAC uses MP4 containers; FLAC uses its own container
Limitations
Some considerations when using ALAC:
- Limited non-Apple support: Less universal support compared to FLAC
- Slightly larger files: Less efficient compression than some competitors
- Less community development: Despite being open source, development is still Apple-centric
- Metadata limitations: Less flexible than FLAC for specialized metadata
High-Resolution Audio in ALAC
ALAC fully supports high-resolution audio:
- 24-bit/96kHz audio for studio-quality reproduction
- 24-bit/192kHz for audiophile applications
- Support for even higher sample rates in specialized applications
Apple Music Lossless
In 2021, Apple Music introduced lossless streaming using the ALAC format, enabling subscribers to stream:
- CD quality (16-bit/44.1kHz) lossless audio
- High-resolution lossless (up to 24-bit/192kHz) on supported devices
Conclusion
ALAC provides an excellent solution for lossless audio playback within the Apple ecosystem. While it may not have the compression efficiency or widespread adoption of FLAC, its seamless integration with Apple devices and software makes it the natural choice for Apple users who want lossless audio quality without compatibility concerns. The format strikes a balance between perfect audio reproduction, reasonable file sizes, and energy-efficient decoding that works particularly well for mobile devices.