What is CAF?
CAF (Core Audio Format) was developed by Apple in 2005 as part of their Core Audio technology. It was designed as a replacement for older audio containers like AIFF and WAV, eliminating their 4GB file size limitation and adding support for more advanced audio features.
Key Features
CAF offers several advantages as an audio container format:
- No practical file size limitations (64-bit file size fields)
- Support for high sample rates and bit depths
- Accommodates a large number of audio channels
- Can store various audio formats, including lossless and lossy compression
- Extensible chunk-based architecture
- Built-in support for metadata and markers
When to Use CAF
CAF is particularly useful for:
- Professional audio work within the Apple ecosystem
- High-resolution audio recordings exceeding 4GB
- Multi-channel audio projects
- Audio applications on macOS and iOS
- Long-duration recordings where WAV would hit size limits
Audio Encodings
CAF can contain audio data in various encodings:
- Linear PCM: Uncompressed audio at various bit depths and sample rates
- Apple Lossless (ALAC): Lossless compression format
- AAC: Advanced Audio Coding for lossy compression
- Other formats: Including iLBC, and various other encodings
Technical Capabilities
CAF files offer extensive technical capabilities:
- Sample rates: From 2 kHz to 192 kHz and beyond
- Bit depths: Up to 32-bit floating point
- Channels: Virtually unlimited channel count
- Duration: Can handle extremely long recordings
Limitations
Some considerations when using CAF:
- Limited compatibility: Primarily used within Apple's ecosystem
- Limited hardware support: Not commonly supported by consumer playback devices
- Software support: Requires specific software for editing and playback outside of Apple platforms
Technical Details
CAF files use the .caf extension. The format uses a chunk-based structure similar to AIFF and WAV, but with 64-bit fields that eliminate size restrictions. CAF files contain a header followed by chunks of data that include audio data, channel layout information, markers, and other metadata. The MIME type is "audio/x-caf".
CAF vs WAV/AIFF
When compared to older audio container formats, CAF offers several advantages:
- No 4GB file size limitation (unlike standard WAV/AIFF)
- Better support for extensive metadata
- Native channel labeling for surround sound and other multi-channel formats
- Closer integration with Apple's audio frameworks
- Support for packet-based audio formats alongside PCM
Conclusion
CAF is a versatile and powerful audio container format that excels in professional audio workflows, especially within Apple's ecosystem. While its cross-platform support is limited, it offers significant technical advantages for high-resolution, multi-channel, and long-duration audio recordings. For professionals working with Apple platforms who need to overcome the limitations of traditional formats like WAV and AIFF, CAF provides an excellent solution.