Convert MXF to AU — Free Online Tool
Convert MXF broadcast files to Sun AU format, extracting the audio stream and encoding it as 16-bit big-endian PCM — a lossless, uncompressed audio format native to Unix systems. Ideal for extracting clean, professional-grade audio from broadcast master files for use in legacy Unix workflows or streaming pipelines.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your MXF file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
Settings
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
MXF (Material Exchange Format) is a professional broadcast container that can carry video, audio, and rich metadata including timecodes and descriptive tracks. During this conversion, FFmpeg discards all video streams from the MXF file entirely and extracts the audio, re-encoding it as PCM signed 16-bit big-endian (pcm_s16be) — the default and most compatible codec for the AU container. If the source MXF audio is already PCM (pcm_s16le is common in MXF), the conversion is essentially a sample format and byte-order change from little-endian to big-endian, with no perceptual quality loss. The AU format uses a minimal fixed header and stores raw PCM data, which makes it structurally simple but also means MXF-specific metadata like timecodes, reel names, and broadcast WAV chunks are not preserved in the output.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg command-line tool, which is running here as a WebAssembly (FFmpeg.wasm) instance entirely within your browser — no data is sent to a server. |
-i input.mxf
|
Specifies the input MXF file. FFmpeg reads the MXF container and identifies all contained streams — typically one or more video streams encoded as H.264, MPEG-2, or MJPEG, and one or more audio streams encoded as PCM or AAC. |
-c:a pcm_s16be
|
Sets the audio codec to signed 16-bit big-endian PCM, which is the native and default encoding for the AU format. This is required because MXF typically stores audio as little-endian PCM (pcm_s16le), and AU expects big-endian byte order as defined by its Sun Microsystems origin. |
output.au
|
Defines the output file as an AU container. FFmpeg infers the AU format from the .au extension and automatically drops all video streams from the MXF input, since AU is a purely audio format with no support for video or complex metadata. |
Common Use Cases
- Extracting clean, uncompressed audio from a broadcast MXF master file to feed into a legacy Unix-based audio processing pipeline that expects AU-format input
- Archiving the audio track from an MXF news package or documentary edit to AU for use on Unix workstations or older digital audio tools that predate WAV support
- Providing audio from professional MXF camera originals to developers building or testing audio streaming applications, since AU was one of the earliest formats supported in Java and early internet audio stacks
- Pulling the dialogue or music track from an MXF file for use in a Sun Solaris or other Unix environment where AU remains the native audio format
- Converting MXF audio captures from broadcast mixers to AU format for ingestion into legacy scientific or audio analysis software that requires simple PCM containers without complex headers
- Stripping the audio from an MXF edit master to a portable, dependency-free PCM file for quality-checking raw audio content before a re-encode or re-packaging step
Frequently Asked Questions
In most cases, no — not perceptibly. MXF broadcast files commonly carry audio encoded as pcm_s16le (16-bit little-endian PCM), and the output AU file uses pcm_s16be (16-bit big-endian PCM). The only change is the byte order of the same 16-bit integer samples, so no audio data is lost or degraded. If your MXF source uses a higher bit depth like pcm_s24le, there will be a downgrade to 16-bit during conversion, which reduces dynamic range slightly.
All video streams are dropped — AU is a purely audio format and cannot contain video. MXF-specific metadata such as timecodes, reel identifiers, descriptive metadata, and broadcast WAV chunk data are also not carried over, as the AU format uses a minimal four-field header (magic number, data offset, data size, encoding, sample rate, channels) and has no mechanism to store professional broadcast metadata. If preserving timecode or other production metadata is important, consider using WAV or MXF itself as the output container instead.
The AU format was developed by Sun Microsystems for its SPARC-based Unix workstations, which used a big-endian processor architecture. Big-endian byte order was therefore the natural choice and became baked into the AU specification. Modern x86 systems are little-endian, which is why formats like WAV and most MXF audio tracks default to pcm_s16le. The byte-order difference is why FFmpeg applies the pcm_s16be codec specifically when targeting AU output.
By default, FFmpeg selects the first audio stream it finds in the MXF file. The AU format does not support multiple audio tracks, so only one stream will be included in the output. If you need a specific audio track from a multi-track MXF file — for example, a particular language track or a surround channel — you can modify the FFmpeg command to add '-map 0:a:1' (replacing 1 with the zero-based index of your desired track) before the output filename.
You can add '-ar 44100' to target a specific sample rate (e.g., 44100 Hz or 48000 Hz) and '-ac 1' or '-ac 2' to set mono or stereo output. For example: 'ffmpeg -i input.mxf -c:a pcm_s16be -ar 44100 -ac 2 output.au'. This is useful if your downstream Unix tool expects a specific sample rate that differs from the MXF source, which is typically 48000 Hz in broadcast contexts.
Yes. On Linux or macOS, you can use a shell loop: 'for f in *.mxf; do ffmpeg -i "$f" -c:a pcm_s16be "${f%.mxf}.au"; done'. On Windows Command Prompt, use: 'for %f in (*.mxf) do ffmpeg -i "%f" -c:a pcm_s16be "%~nf.au"'. This processes each MXF file in the current directory and produces a matching AU file with the same base filename. This is particularly helpful when working with a batch of MXF news packages or broadcast segments.
Technical Notes
The AU format's simplicity is both its strength and its limitation in this context. It supports a small fixed set of encodings — pcm_s16be being the most universally compatible — and has no provision for extensible metadata, making it unsuitable as an archival replacement for MXF. The output file will be strictly larger in bitrate terms than a compressed MXF audio track (e.g., AAC at 192k), since pcm_s16be at 48000 Hz stereo produces approximately 1.5 Mbps of uncompressed audio. AU files also do not support multi-channel audio beyond stereo in most implementations, so surround mixes from broadcast MXF sources will need to be downmixed or remapped explicitly. Note that FFmpeg does not have a quality control parameter that meaningfully applies to PCM codecs in AU output — the '-b:a' flag is irrelevant for uncompressed PCM since the bitrate is determined entirely by sample rate and bit depth. For the most accurate reproduction of professional MXF audio at full 24-bit depth, consider exporting to WAV with pcm_s24le instead, as AU's practical ecosystem support for 24-bit PCM is inconsistent across platforms.