REWINDCAF (Core Audio Format) files on iPhone
CAF is Apple's Core Audio Format, a flexible audio container that can hold many codecs and has no 4 GB size limit. It mostly appears in Apple's developer and production workflows. REWIND plays CAF files that you import from the Files app.
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What is CAF?
Core Audio Format is a container Apple introduced with Mac OS X Tiger in 2005. A container describes how audio is stored, not how it is compressed, so a CAF file can hold uncompressed PCM, AAC, ALAC and other encodings. It was designed to avoid the 4 GB limit of formats such as WAV and AIFF. Background: CAF on Wikipedia.
Where do CAF files come from?
Most people meet CAF through Apple tools: audio recorded or exported by developer utilities, or sound effects bundled in apps. Few music stores sell CAF. If a CAF file ends up in your folder, it is probably something you made or exported.
Typical sizes
Size depends on what is inside. A CAF with uncompressed CD-quality PCM takes about 10.6 MB per minute, like WAV. A CAF with AAC or ALAC takes the size of that codec. Because of that, it is impossible to give a single number for the format.
How do I get CAF onto an iPhone and into REWIND?
REWIND supports CAF, so you do not need to convert it. If you would rather have a more common type, export to AAC/M4A or ALAC from your audio tool.
- Place the .caf file in iCloud Drive, AirDrop it or transfer from a Mac.
- Open REWIND and import from the Files app.
- Play it on any machine.
The 4 GB limit explained
Formats like WAV and AIFF store sizes in 32-bit fields, which caps a file at about 4 GB. At CD quality that is more than 6 hours, which is plenty for music and not enough for long multichannel recordings. CAF uses 64-bit sizes, so that ceiling is far away. For a phone library it will not matter.
Tags and compatibility
Tag support inside CAF is limited compared with M4A or FLAC, so a track may show with less information. Outside Apple's ecosystem few players open CAF at all. If you plan to share the files, export a copy as AAC/M4A or MP3.
Frequently asked questions
What is a CAF file?
A CAF file uses Apple's Core Audio Format container, which can hold different audio encodings and has no 4 GB limit.
Does REWIND play CAF?
Yes. Import CAF files from the Files app.
Is CAF lossless?
It depends on what is inside. CAF can hold lossless or lossy audio.
Should I convert CAF to MP3?
Not needed for REWIND. It plays CAF directly.
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