Convert DVR to AU — Free Online Tool
Convert DVR surveillance or broadcast recordings to Sun AU format, extracting the audio stream and encoding it as uncompressed PCM (pcm_s16be) — a 16-bit big-endian format native to Unix systems. This tool strips the video entirely and produces a raw, headerless-style audio file suitable for 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
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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
DVR files typically store video encoded with H.264 (libx264) and audio encoded with AAC, a lossy compressed format. During this conversion, FFmpeg discards the video stream entirely and decodes the AAC audio, then re-encodes it into PCM signed 16-bit big-endian (pcm_s16be) — the default and most compatible codec for the AU container. This is a lossy-to-lossless-PCM transcode: the AAC compression artifacts from the original DVR recording are preserved in the decoded audio, but no additional lossy compression is applied in the output. The resulting .au file has a simple Sun AU header followed by raw PCM audio data, making it straightforward to parse on Unix systems or feed into audio processing tools.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, which handles all demuxing, decoding, and encoding steps needed to convert the DVR file to AU format entirely within your browser via WebAssembly. |
-i input.dvr
|
Specifies the input DVR file. FFmpeg will demux this proprietary container to extract its H.264 video and AAC audio streams, though only the audio stream will be used in this conversion. |
-c:a pcm_s16be
|
Sets the audio codec to PCM signed 16-bit big-endian, which is the native and most compatible audio encoding for the Sun AU container. This decodes the DVR's AAC audio and re-encodes it as uncompressed PCM with no further quality loss. |
output.au
|
Specifies the output filename with the .au extension, which tells FFmpeg to use the Sun AU container format. The video stream from the DVR file is automatically dropped because AU is an audio-only format. |
Common Use Cases
- Extracting audio from surveillance DVR footage to use as evidence in a legal or insurance context where a simple, uncompressed audio format is required for archival integrity
- Pulling broadcast-captured audio from a DVR recording into a legacy Unix or Linux audio processing pipeline that expects Sun AU files
- Converting a DVR recording's audio track to uncompressed PCM AU for waveform analysis or forensic audio examination, where AAC compression would obscure fine details
- Feeding DVR-captured audio into older Unix-based media servers or telephony systems that natively support the AU format for streaming
- Archiving the audio commentary or ambient sound from a broadcast capture in a format that is trivially simple to decode without proprietary codecs
- Preparing DVR audio for import into scientific or academic audio tools (such as those used in phonetics research) that accept Sun AU as a standard input format
Frequently Asked Questions
The original DVR file stores audio as AAC, which is a lossy format — so some audio quality was already lost when the DVR captured the recording. During this conversion, FFmpeg decodes the AAC stream and outputs it as uncompressed PCM (pcm_s16be), which introduces no additional compression or quality loss. The output AU file is an accurate PCM representation of whatever audio the AAC codec preserved, but it cannot recover detail that AAC discarded during the original recording.
The DVR's AAC audio is heavily compressed — a typical 128 kbps AAC stream stores far less data per second than uncompressed PCM. The output AU file stores audio as raw 16-bit big-endian PCM at the full sample rate, which produces roughly 1.4 MB per minute per channel at 44.1 kHz. This size increase is expected and is the nature of decompressing a lossy codec into an uncompressed container.
No. The Sun AU format has an extremely minimal header that stores only basic audio parameters: encoding type, sample rate, channel count, and an optional short annotation field. DVR-specific metadata such as recording timestamps, camera IDs, or channel labels has no corresponding field in the AU spec and will be lost during conversion. If preserving this metadata is important, you should record it separately before converting.
Yes. The AU container supports several codecs including pcm_s8, pcm_u8, pcm_alaw, and pcm_mulaw in addition to the default pcm_s16be. To use mu-law encoding (common in telephony applications), modify the command to: ffmpeg -i input.dvr -c:a pcm_mulaw output.au. Note that pcm_mulaw and pcm_alaw are lossy and will reduce audio fidelity compared to the default pcm_s16be.
On Linux or macOS, you can loop over files in a directory with: for f in *.dvr; do ffmpeg -i "$f" -c:a pcm_s16be "${f%.dvr}.au"; done. On Windows Command Prompt, use: for %f in (*.dvr) do ffmpeg -i "%f" -c:a pcm_s16be "%~nf.au". This processes each DVR file individually and names the output after the source file.
The Sun AU format is a pure audio container — it has no provision for storing video data, subtitles, or any non-audio stream. FFmpeg automatically omits the video stream when the output format cannot contain it. If you need to retain the video, you would need to convert to a different output format such as WAV (for audio-only) or keep the DVR/MP4 container.
Technical Notes
The Sun AU format (.au) was developed by Sun Microsystems and is one of the oldest structured audio file formats still in use. Its header is just 24 bytes, making it trivially simple to parse, but also severely limited in metadata capacity. The default codec used here, pcm_s16be (signed 16-bit big-endian PCM), stores audio at full resolution with no compression, which contrasts sharply with the AAC audio typically found in DVR files. Big-endian byte order is a legacy of SPARC and other big-endian Unix architectures; on modern x86 systems, most tools handle the byte-order conversion transparently. One important limitation: the AU format does not support multiple audio channels beyond what the codec allows, and DVR files typically contain only mono or stereo audio, so channel layout is usually preserved without issue. Because DVR is a proprietary format with vendor-specific variations, FFmpeg may not correctly demux all DVR files — if the tool reports a demuxing error, the DVR file may use a proprietary encryption or container variant that FFmpeg cannot parse. No chapter markers, subtitle tracks, or embedded timestamps from the DVR recording survive in the AU output.