AAC vs CAF
A detailed comparison of AAC Audio and Apple Core Audio — file size, quality, compatibility, and which format to choose for your workflow.
AAC Audio
Audio FilesAAC is a lossy audio codec that delivers better sound quality than MP3 at similar bitrates. It is the default audio format for Apple Music, YouTube, and most streaming services.
About AAC filesApple Core Audio
Audio FilesCAF (Core Audio Format) is Apple audio container supporting any codec.
About CAF filesStrengths Comparison
AAC Strengths
- Better quality than MP3 at equal bitrate — the industry standard since 2000s.
- Universally supported on every smartphone, OS, and browser.
- Efficient on battery thanks to widespread hardware decoding.
- Scales from 8 kbps speech (HE-AACv2) to lossy-transparent 320 kbps.
- Five-channel + LFE surround support out of the box.
CAF Strengths
- Unlimited file size (64-bit offsets).
- Can hold any Core Audio codec (PCM, ALAC, AAC, etc.).
- Native Apple ecosystem support.
- Rich annotation and metadata capabilities.
Limitations
AAC Limitations
- Patent-encumbered — encoders have licensing fees, which is why open alternatives (Opus, Vorbis) exist.
- Slightly more complex to encode than MP3.
- Raw .aac streams carry no seek index — tooling often prefers M4A/MP4 containers.
- Lossy — not suitable for archival or studio production.
CAF Limitations
- macOS/iOS-centric — limited non-Apple tool support.
- Not a delivery format — exists for workflow, not consumption.
- Proprietary but documented.
- No broad industry adoption; WAV / BWF dominate interchange.
Technical Specifications
| Specification | AAC | CAF |
|---|---|---|
| MIME type | audio/aac | audio/x-caf |
| Extensions | .aac, .m4a, .mp4 (container-dependent) | — |
| Standard | ISO/IEC 14496-3 | — |
| Variants | AAC-LC, HE-AAC, HE-AACv2, AAC-LD, xHE-AAC | — |
| Sample rates | 8-96 kHz | — |
| Extension | — | .caf |
| Container | — | Chunked, 64-bit sizes |
| Codecs | — | PCM, ALAC, AAC, IMA ADPCM, µ-law, Opus, FLAC |
| Max size | — | 2^64 bytes (effectively unlimited) |
Typical File Sizes
AAC
- Speech podcast (64 kbps) 1 MB/min
- 3-min music track (128 kbps) 3 MB
- 3-min music track (256 kbps) 6 MB
- Broadcast-quality 5.1 (384 kbps) 9 MB for 3 min
CAF
- iOS app sound effect (short) 10-200 KB
- 1 hour Logic Pro track (24-bit 48 kHz) ~620 MB
- Multi-track session (10 hours, 32 tracks) 100+ GB
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Frequently Asked Questions
AAC (Advanced Audio Coding) is a lossy audio format standardized by ISO as the successor to MP3. It delivers better sound quality than MP3 at equivalent bitrates and is the default audio format for Apple products, YouTube, and most streaming services.
AAC (Advanced Audio Coding) is a com perdas audio formato padrãoized by ISO como o successor to MP3. It delivers better sound quality than MP3 at equivalent bitrates e is the default audio formato para Apple products, YouTube, e most streaming services.
AAC files play in iTunes, Apple Music, VLC, Windows Media Player, and all modern web browsers. AAC is natively supported on iOS, Android, macOS, and Windows.
AAC arquivos reproduzir in iTunes, Apple Music, VLC, Windows Media Player, e all moderno web browsers. AAC is natively suportado no iOS, Android, macOS, e Windows.
AAC is technically superior, offering better quality at the same bitrate. Use AAC for Apple ecosystem and modern devices. Use MP3 only when you need compatibility with very old hardware like legacy car stereos or basic MP3 players.
AAC is technically superior, offering better quality at the same bitrate. usar AAC para Apple ecosystem e dispositivos modernoos. usar MP3 only when you need compatibilidade com very old hardware like legacy car stereos ou basic MP3 players.