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Supports: CAF
CAF is Apple's Core Audio Format — an audio container, not a video file. AVI (Audio Video Interleave) is a Microsoft video container from 1992 that carries a moving picture, usually an MPEG-4 (DivX or Xvid) video track, alongside an audio track. A standard .caf holds only sound — a voice memo, a GarageBand loop, an iMessage audio clip — so there is no picture or motion inside it to encode into an AVI video. This tool is wired as a video target (it defaults to the MPEG-4 video codec and shows controls for resolution, bitrate, and trim), and an audio-only file has no frames to fill those with. This page explains what a CAF really is and points you to the tools that do what you actually want.
| Property | Value |
|---|---|
| Format name | Core Audio Format (CAF) |
| Type | Audio container (no video, no image) |
| Developer | Apple |
| Introduced | 2005, with Mac OS X 10.4 (Tiger) |
| Internet media type | audio/x-caf |
| Typical payloads | Linear PCM, Apple Lossless (ALAC), AAC, and other audio codecs |
| Maximum size | No 4 GB cap — uses 64-bit file offsets, so one file can hold an extremely long recording |
| Common sources | GarageBand / Logic Pro / Soundtrack Pro loops and sound effects, iMessage audio messages |
| Best replacement for | AIFF and WAV when a lossless container without the 4 GB limit is needed |
In the CAF specification, the word "frame" means an audio sample frame — one sample for each channel, played together — not a video frame. Apple's spec even notes this definition "might be different from the use of the term 'frame' by codecs, video files, and audio or video processing applications." That naming overlap, plus AVI's job as a video container, is the only reason a "CAF to AVI" route appears in some format lists at all. There is no sequence of pictures inside an audio file to turn into video.
| Property | Value |
|---|---|
| Format name | Audio Video Interleave (AVI) |
| Type | Video container (video track plus optional audio) |
| Developer | Microsoft, as part of Video for Windows |
| Introduced | November 1992 |
| Internet media type | video/vnd.avi (also seen as video/x-msvideo) |
| Common video codecs | MPEG-4 ASP (DivX, Xvid), and many others |
| What it stores | Interleaved chunks of video frames and audio samples for synchronized playback |
| Needs a video stream? | Yes — AVI is built around a picture track; an audio-only input leaves nothing to interleave |
Because AVI is built around a video stream and a standard CAF describes only sound, there is no picture payload to transcode between them. An AVI assembled from a pure audio file has no frames to show.
.caf does not get on Windows..caf) and convert that to AVI. A Core Audio file has no frames, so a video must already exist to wrap as AVI.Because an AVI is built around a video track and a standard .caf is pure audio — there are no pictures inside to interleave as video. This tool defaults to the MPEG-4 video codec, so an audio-only input has nothing to fill the picture with. The job only produces a usable AVI if the specific file you uploaded happens to carry a real video stream, which ordinary Core Audio recordings do not.
CAF (Core Audio Format) is an audio container developed by Apple and introduced in 2005 with Mac OS X 10.4, using the media type audio/x-caf. It can hold Linear PCM, Apple Lossless (ALAC), AAC, and other audio codecs. It is not a video or image format, so it cannot be turned into an AVI video.
The route comes from a format-list quirk: AVI is one of xconvert's video output targets, and the tool's metadata pairs the .caf input with it the same way it pairs every video format. That pairing does not mean a Core Audio recording contains video — it does not. We keep the page to explain the mismatch and send you to the audio targets that actually do what you want, rather than silently producing an empty file.
For everyday use, convert to MP3 for the smallest, most compatible file, or to WAV to keep it lossless and uncompressed. In our testing, a short ALAC-based .caf voice clip converted to MP3 lands in the low hundreds of kilobytes while staying clearly intelligible. See the full set of audio targets on the audio converter.
Not usefully. AVI was designed by Microsoft in 1992 to interleave a video track with audio for synchronized playback, so it expects a picture stream. A few tools can write an audio-only AVI, but almost nothing plays it as music, which is why sound belongs in an audio format such as MP3, WAV, or FLAC instead.
No. WAV is effectively capped near 4 GB by its 32-bit size fields — which can be as little as about 15 minutes of high-resolution audio — but CAF uses 64-bit file offsets, so a single .caf file can store an extremely long recording without hitting that ceiling. That capacity is one of the reasons Apple created the format as a successor to AIFF and WAV.
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