Convert AIF to AU — Free Online Tool
Convert AIF audio files to AU format using the pcm_s16be codec, producing a simple uncompressed audio file compatible with Unix systems and legacy Sun Microsystems environments. This tool runs entirely in your browser — no uploads, no servers, completely private.
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FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your AIF file here
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Note: Browser-based encoding uses approximate quality targets. For precise CRF compression, copy the FFmpeg command above and run it on your desktop.
Estimated output:
Conversion Complete!
DownloadHow It Works
AIF and AU are both uncompressed PCM audio containers, so this conversion is primarily a container swap rather than a re-encoding operation. The AIF file's PCM audio stream (which may be 16-bit, 24-bit, 32-bit, or floating-point depending on the source) is decoded and re-encoded as pcm_s16be — 16-bit signed big-endian PCM — and written into the AU container with its minimal fixed-length header. Because AU format's codec support is more limited than AIF's, any source audio encoded in higher bit-depth formats like pcm_s24be or pcm_s32be will be downsampled to 16-bit during this process. The sample rate and channel count are preserved. The resulting .au file has a simple 28-byte header followed by raw PCM data, making it a very lightweight and portable format.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg command-line tool. In this browser tool, FFmpeg runs locally via WebAssembly (FFmpeg.wasm), so no files leave your device — the same binary logic executes entirely in your browser. |
-i input.aif
|
Specifies the input file in AIF format. FFmpeg reads the IFF chunk structure to locate the COMM chunk (audio parameters) and SSND chunk (raw PCM audio data) inside the AIF container. |
-c:a pcm_s16be
|
Sets the audio codec to 16-bit signed big-endian PCM, the default and most compatible audio encoding for the AU container. This ensures the output is a straightforward uncompressed audio stream that any AU-compatible player can decode without additional libraries. |
output.au
|
Specifies the output filename with the .au extension. FFmpeg uses this extension to select the Sun AU muxer, which writes the 28-byte AU header followed by the raw pcm_s16be audio data, producing a valid .au file for Unix and legacy Java environments. |
Common Use Cases
- Preparing audio files for playback on legacy Unix or Solaris workstations that natively support AU but not AIF
- Supplying audio assets to older Java applications or applets that use the javax.sound API, which has historically favored the AU format
- Converting Apple-native AIF recordings into AU format for use with Unix-based audio processing pipelines or scientific software
- Creating AU audio samples for use with NeXTSTEP or OpenStep software environments that expect Sun AU files
- Reducing AIF file complexity by stripping Apple-specific metadata and producing a bare-bones PCM audio file for archival or analysis purposes
- Generating AU files from AIF masters for compatibility with older web server audio streaming setups that served .au files
Frequently Asked Questions
If your AIF source file uses pcm_s16be (standard 16-bit audio), there is no quality loss — the PCM audio data is preserved exactly. However, if your AIF was recorded at a higher bit depth like 24-bit (pcm_s24be) or 32-bit (pcm_s32be), the conversion to AU's 16-bit pcm_s16be will reduce dynamic range from 144dB to approximately 96dB. For most listening purposes this is still excellent quality, but audiophile or mastering-grade sources will lose some headroom.
Yes, the AU format supports multiple channels including stereo. Your stereo AIF file will be converted to a stereo AU file without any downmixing. The AU container encodes channel count in its header, so compliant players will correctly identify and play back both channels.
AU has an extremely minimal header — it stores only sample rate, channel count, bit depth, and a short optional annotation string. The rich metadata that AIF can carry, including artist tags, album info, loop markers, and instrument chunks, is not preserved in the AU container. If metadata retention is important, you should store the original AIF file separately before converting.
Yes. The AU format supports pcm_alaw and pcm_mulaw, which are lossy companded codecs commonly used in telephony. To use them, replace '-c:a pcm_s16be' with '-c:a pcm_alaw' or '-c:a pcm_mulaw' in the command. These codecs produce smaller files but at the cost of significantly reduced audio fidelity — they are 8-bit logarithmic encodings originally designed for voice, not music or high-quality audio.
The single-file command shown works for one file at a time. To batch convert on the command line, you can use a shell loop — on Linux or macOS: 'for f in *.aif; do ffmpeg -i "$f" -c:a pcm_s16be "${f%.aif}.au"; done'. On Windows Command Prompt: 'for %f in (*.aif) do ffmpeg -i "%f" -c:a pcm_s16be "%~nf.au"'. The browser-based tool processes files individually.
AU files have a very compact 28-byte header compared to AIF's more elaborate chunk-based structure. If your AIF source was 16-bit, the raw audio data size will be nearly identical, but the AU file will be slightly smaller due to the stripped metadata and simpler container overhead. If your AIF was recorded at 24-bit or 32-bit, the AU output will be noticeably smaller because the audio is downconverted to 16-bit, reducing two or four bytes per sample to two bytes per sample.
Technical Notes
AIF uses an IFF-based chunk structure (COMM, SSND, and optional metadata chunks) and supports big-endian PCM at 8, 16, 24, and 32-bit depths as well as floating-point. AU (also known as .snd) is one of the oldest digital audio formats, developed by Sun Microsystems, and uses a fixed-length 28-byte header encoding sample rate, channel count, encoding type, and an optional comment. The pcm_s16be codec used in this conversion is natively big-endian, which aligns naturally with both formats' big-endian heritage — AIF was designed for Motorola 68k Macs and AU for SPARC workstations, both big-endian architectures. AU does not support ID3 tags, AIFF metadata chunks, or any embedded cover art. The format is best suited for simple, portable raw PCM storage or legacy system compatibility rather than modern media workflows. Note that AU files are not natively supported by most modern consumer media players on Windows or macOS without additional codecs, but they play reliably in Unix/Linux environments via tools like aplay, SoX, or FFmpeg itself.