What is a ALAC file?
The Apple Lossless Audio Codec, commonly known as ALAC, is a high-efficiency audio format that utilizes the MPEG-4 compliant QuickTime container (.m4a). Initially launched as a proprietary technology in 2004, Apple transitioned ALAC to an open-source and royalty-free model in 2011, significantly broadening its accessibility. This format provides a perceptible audio upgrade over lossy codecs like AAC and MP3 by preserving all the original data. While functionally similar to FLAC (Free Lossless Audio Codec), ALAC typically achieves a slightly different compression ratio. For playback, ALAC-encoded files are natively supported on Apple devices through QuickTime and iTunes (now Apple Music), and can be played on Microsoft Windows Media Player with the addition of the K-Lite codec pack.
Key Characteristics of ALAC Files
| Characteristic | Description |
|---|---|
| Audio Quality | Lossless & High-Fidelity. Perfectly identical to the original source. |
| File Size | Medium. Smaller than WAV/AIFF, but larger than MP3/AAC. An ideal balance of quality and size. |
| Compatibility | Excellent in Apple Ecosystem. Good elsewhere, with growing support on platforms like Android and Windows via players like VLC |
| Primary Use Case | Apple Users & Audiophiles. Ideal for building a high-quality music library on Apple devices without wasting storage. |
| File Extension | .m4a (same as AAC, but the codec inside is different). |
ALAC File Format
Files based on the ALAC codec are binary files that is available as open source on GitHub for developer’s reference. It contains the sources for the ALAC encoder and decoder. Apple has also provided a command line utility, called alacconvert, to read and write the audio data to/from Core Audio Format (CAF) and WAVE files. Following are some key points about the ALAC file format.
Bit Depths- 16, 20, 24 and 32 bits.Sample Rate- Any arbitrary integer sample rate from 1 to 384,000 Hz. Theoretical rates of up to 4,294,967,295 (2^32 - 1) Hz could be supported.Packet Size- The default packet size defaults to 4096 sample frames of audio per packet. Other packet sizes are certainly possible. However, non-default packet sizes are not guaranteed to work properly on all hardware devices that support Apple Lossless. Packets above 16,384 sample frames are not supported.Supported Channels- It supports one to eight channels. Each channel has the following order of information.
| Num Chan | Order |
|---|---|
| 1 | mono |
| 2 | stereo (Left, Right) |
| 3 | MPEG 3.0 B (Center, Left, Right) |
| 4 | MPEG 4.0 B (Center, Left, Right, Center Surround) |
| 5 | MPEG 5.0 D (Center, Left, Right, Left Surround, Right Surround) |
| 6 | MPEG 5.1 D (Center, Left, Right, Left Surround, Right Surround, Low Frequency Effects) |
| 7 | Apple AAC 6.1 (Center, Left, Right, Left Surround, Right Surround, Center Surround, Low Frequency Effects) |
| 8 | MPEG 7.1 B (Center, Left Center, Right Center, Left, Right, Left Surround, Right Surround, Low Frequency Effects) |
FAQ
Q1: Is ALAC better quality than AAC?
A: Yes, ALAC is a lossless format that preserves all original audio data, while AAC is a lossy format that compresses by removing some audio information.
Q2: Can Android phones play ALAC files?
A: While not natively supported by all Android devices, many third-party music player apps like VLC Media Player can play ALAC files without any issue.
Q3: Does Spotify or Apple Music use ALAC?
A: Apple Music uses ALAC to deliver its Lossless tier to subscribers. Spotify currently uses lossy formats (Ogg Vorbis), but has announced a future “HiFi” tier.
Q4: Should I rip my CDs to ALAC?
A: Yes, if you are an Apple user and want to create a perfect, future-proof digital archive of your CDs, ripping them to ALAC is an excellent choice.
Q5: How do I convert a FLAC file to ALAC?
A: You can easily convert FLAC to ALAC using software like XLD (X Lossless Decoder) on Mac or dBpoweramp on Windows, making your library compatible with Apple devices.
