Extract Audio from MOV to AU — Free Online Tool
Extract audio from MOV files and save it as AU format — a raw PCM audio container developed by Sun Microsystems for Unix systems. This tool strips the video stream entirely and encodes the audio as 16-bit big-endian PCM (pcm_s16be), producing an uncompressed, lossless AU file directly in your browser.
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FFmpeg Command
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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
MOV files typically store audio in compressed formats such as AAC or MP3 alongside a video stream. During this conversion, FFmpeg discards the video stream entirely using the -vn flag, then decodes whatever audio codec is present in the MOV container and re-encodes it as pcm_s16be — 16-bit signed big-endian pulse-code modulation — written into a Sun AU container. Because the MOV source audio (usually AAC) is lossy, it is fully decoded to raw PCM before being written to AU, which means the AU file preserves the audio with no further quality loss beyond what the original AAC encoding introduced. The AU format uses a simple fixed header with no support for chapters, multiple tracks, or embedded metadata beyond basic sample rate and channel count.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg command-line tool — the same underlying engine running as WebAssembly in your browser. The command shown here is exactly what executes locally when you use this page, and you can paste it directly into a terminal to process files larger than 1GB on your own machine. |
-i input.mov
|
Specifies the input file — a MOV container, which may contain video encoded as H.264 or HEVC alongside audio encoded as AAC, MP3, FLAC, or other codecs depending on the source application that created it. |
-vn
|
Disables all video streams in the output — essential here because AU is a pure audio format with no support for video data. Without this flag, FFmpeg would attempt to include the video stream and fail, since AU has no video encoding defined. |
-c:a pcm_s16be
|
Sets the audio codec to pcm_s16be — 16-bit signed big-endian pulse-code modulation — which is the native and default encoding of the Sun AU format. FFmpeg decodes the source MOV audio (typically AAC) to raw PCM and writes it in big-endian byte order to match the AU specification. |
output.au
|
Specifies the output filename with the .au extension, which tells FFmpeg to use the Sun AU container format. FFmpeg writes the minimal AU header — encoding type, sample rate, and channel count derived from the source MOV audio stream — followed by the raw pcm_s16be audio data. |
Common Use Cases
- Providing audio samples to legacy Unix or Solaris workstation software that only accepts Sun AU files as input
- Preparing audio assets for Java applets or older Java-based applications, which historically used AU as their native audio format via the AudioClip API
- Extracting uncompressed audio from a MOV video recorded on a Mac or iPhone for analysis in scientific or signal-processing tools that require raw PCM in AU format
- Archiving audio from QuickTime MOV files in a format-agnostic, uncompressed container for long-term storage on Unix-based systems
- Stripping audio from a Final Cut Pro or DaVinci Resolve MOV export to create a standalone audio reference file for voice-over timing or quality checking on Unix infrastructure
Frequently Asked Questions
It depends on what audio codec is stored inside the MOV file. Most MOV files — especially those from iPhones, QuickTime, or Final Cut Pro — use AAC audio, which is a lossy codec. When converting to AU, FFmpeg decodes the AAC audio back to raw PCM and writes it as pcm_s16be. No additional quality loss is introduced during this step, but the quality damage from the original AAC encoding is already baked in. If your MOV file happens to contain lossless audio like FLAC or uncompressed PCM, the resulting AU file will be a true lossless representation.
The AU format stores audio as uncompressed PCM, meaning every sample is stored as a raw numeric value with no compression whatsoever. A MOV file typically contains AAC audio, which achieves compression ratios of 10:1 or more. When that compressed audio is decoded and written as pcm_s16be in the AU container, the audio track alone can be many times larger than it was inside the MOV. For example, one minute of stereo audio at 44.1kHz stored as 16-bit PCM occupies roughly 10 MB, whereas the same audio compressed as 128k AAC would be under 1 MB.
Yes. FFmpeg reads the sample rate and channel configuration from the MOV audio stream and writes those values into the AU file header automatically. The AU format header stores sample rate, number of channels, and encoding type, so a stereo 44.1kHz MOV will produce a stereo 44.1kHz AU file. However, AU does not support metadata fields like track title, artist, album, or any of the extensive metadata atoms that MOV containers can carry, so all of that information is lost.
Yes. The AU format supports several audio encodings beyond pcm_s16be, including pcm_s8, pcm_u8, pcm_alaw, and pcm_mulaw. To use mu-law encoding — common in telephony applications — you would change the command to: ffmpeg -i input.mov -vn -c:a pcm_mulaw output.au. The pcm_mulaw and pcm_alaw codecs produce smaller files than pcm_s16be but with reduced dynamic range, and they are typically used for voice audio rather than music or high-fidelity recordings.
On a Unix or macOS system, you can loop over all MOV files in a directory with a shell one-liner: for f in *.mov; do ffmpeg -i "$f" -vn -c:a pcm_s16be "${f%.mov}.au"; done. On Windows PowerShell: Get-ChildItem *.mov | ForEach-Object { ffmpeg -i $_.FullName -vn -c:a pcm_s16be ($_.BaseName + '.au') }. Each input MOV file will produce a corresponding AU file with the same base name. This is especially useful for the browser tool's 1GB file limit — larger MOV files can be batch-processed locally using the same command displayed on this page.
AU files can still be played on most modern systems, though support is more limited than for WAV or FLAC. macOS can open AU files natively via QuickTime Player and Core Audio. On Linux, players like VLC, ffplay, and Audacity all support AU. Windows has no built-in AU support, but VLC and Audacity handle it reliably. For anything beyond simple playback — editing, streaming, or broad sharing — you would be better served converting the MOV to WAV or FLAC instead, as AU is primarily useful when a specific legacy Unix application or Java environment requires it.
Technical Notes
The Sun AU format was designed in the early 1990s by Sun Microsystems and features an intentionally minimal fixed-size header containing the data offset, data size, encoding type, sample rate, and channel count — nothing more. It has no support for ID3 tags, Vorbis comments, or any extensible metadata scheme, so all QuickTime metadata atoms present in the MOV source (title, creation date, GPS coordinates from iPhone recordings, color space information) are silently discarded during conversion. The default codec written by FFmpeg is pcm_s16be — 16-bit signed PCM stored in big-endian byte order, which reflects the format's origin on SPARC and other big-endian architectures. This is different from WAV, which uses little-endian byte order (pcm_s16le). Software expecting WAV will not correctly read an AU file even if both contain 16-bit PCM, because the byte order and header structure differ. The AU format does not support multiple audio tracks, so if the source MOV contains multiple audio streams (e.g., a stereo mix plus a separate surround track), only the first audio stream is extracted. There is no audio bitrate parameter relevant to pcm_s16be, as uncompressed PCM bitrate is determined entirely by sample rate and channel count, not a configurable quality setting.