Extract Audio from DVR to AU — Free Online Tool
Extract audio from DVR recordings and save it as a Sun AU file with uncompressed PCM audio. This tool strips the video stream entirely and decodes the DVR's AAC audio to raw 16-bit big-endian PCM — the native encoding of the AU format — making it ideal for Unix-based audio workflows or archival purposes.
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FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
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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
DVR files typically carry AAC-encoded audio alongside an H.264 video stream, recorded by digital video recorders used in surveillance or broadcast capture systems. During this conversion, FFmpeg discards the video stream entirely and decodes the compressed AAC audio track. The decoded PCM samples are then re-encoded as 16-bit signed big-endian PCM and wrapped in Sun's AU container format. Unlike a simple remux, this is a full audio transcode — AAC is a lossy compressed format while AU with pcm_s16be is uncompressed, so the output will be significantly larger than the source audio but will not introduce any additional lossy compression artifacts beyond what was already present in the DVR recording.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In the browser-based version of this tool, FFmpeg runs as a WebAssembly binary entirely within your browser — no data is sent to any server. |
-i input.dvr
|
Specifies the input DVR file. FFmpeg will demux the container to access the separate video and audio elementary streams stored inside the DVR recording. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore the H.264 video stream in the DVR file. Since this is an audio extraction tool, the video data is discarded and not written to the AU output. |
-c:a pcm_s16be
|
Decodes the DVR's AAC audio and re-encodes it as signed 16-bit big-endian PCM — the standard uncompressed audio encoding used in Sun AU files, ensuring maximum compatibility with Unix audio tools and forensic software. |
output.au
|
Sets the output filename with the .au extension, which tells FFmpeg to wrap the pcm_s16be audio stream in the Sun AU container format with its characteristic minimal fixed-length file header. |
Common Use Cases
- Extracting audio from surveillance DVR footage for use as evidence in legal proceedings where uncompressed audio files are required by the court or forensic analyst
- Feeding DVR-captured broadcast audio into legacy Unix or Sun Solaris audio processing pipelines that natively read AU files
- Archiving the audio track from broadcast capture DVR recordings in an uncompressed format to prevent further generational quality loss during editing
- Stripping audio from DVR security footage to analyze for voice identification or ambient sound forensics using tools that accept PCM AU input
- Converting DVR audio for use with older Unix workstation audio software or hardware samplers that predate modern codec support and require raw PCM in AU containers
- Preparing audio extracted from DVR recordings for import into scientific or academic audio analysis tools that expect simple headerless or minimally-headered PCM files like AU
Frequently Asked Questions
No — the original AAC audio in the DVR file is lossy, and that quality ceiling is permanent. Converting to AU with pcm_s16be produces an uncompressed file, which means no additional quality is lost in this conversion, but it also cannot recover detail that AAC compression already discarded. The output is essentially a lossless copy of what the AAC decoder produces, not a restoration of the original analog or uncompressed audio.
The AAC audio codec in DVR files uses perceptual compression, typically achieving roughly 10:1 or greater compression ratios compared to raw PCM. The AU format with pcm_s16be stores every audio sample uncompressed at 16 bits per sample, so a 10-minute DVR audio track encoded at 128k AAC might expand to over 100MB as uncompressed AU. This is expected behavior and the tradeoff for having a fully uncompressed, decoder-independent audio file.
The output AU file uses pcm_s16be — signed 16-bit PCM samples stored in big-endian byte order. This is the default and most universally supported codec within the AU format. Most professional audio software, Unix audio tools, and DAWs can read it, though some Windows-native applications may struggle with the big-endian byte ordering. If you need little-endian PCM for Windows tools, WAV would be a more practical output format.
No. The AU format has an extremely minimal header — it stores only basic audio parameters like sample rate, channel count, encoding type, and an optional plain-text annotation field. DVR-specific metadata such as recording timestamps, camera identifiers, or channel labels embedded in the DVR container will not be carried over to the AU file. If metadata preservation is important, you should record it separately before conversion.
Replace pcm_s16be in the command with another AU-compatible codec. For example, use -c:a pcm_mulaw for G.711 mu-law encoding (common in telephony), -c:a pcm_alaw for A-law encoding, -c:a pcm_s8 for 8-bit signed PCM, or -c:a pcm_u8 for 8-bit unsigned PCM. The full command would look like: ffmpeg -i input.dvr -vn -c:a pcm_mulaw output.au. Note that mu-law and A-law are lossy formats originally designed for voice telephony and will reduce quality compared to pcm_s16be.
Yes. On Linux or macOS, you can use a shell loop: for f in *.dvr; do ffmpeg -i "$f" -vn -c:a pcm_s16be "${f%.dvr}.au"; done. On Windows Command Prompt, use: for %f in (*.dvr) do ffmpeg -i "%f" -vn -c:a pcm_s16be "%~nf.au". This will process each DVR file in the current directory and produce a matching AU file. The browser-based tool processes one file at a time, so the FFmpeg command is the recommended approach for bulk conversions.
Technical Notes
The Sun AU format was developed by Sun Microsystems and became a de facto standard on Unix systems in the late 1980s and 1990s. Its header is intentionally minimal — a 24-byte fixed header plus an optional variable-length annotation — which makes it trivial for software to parse but means it carries almost none of the metadata richness of modern containers. The pcm_s16be codec stores samples as big-endian 16-bit integers, which is the native byte order of SPARC and other big-endian architectures AU was originally designed for; this can cause silent playback failures on some little-endian x86 software that doesn't properly handle byte order flags. DVR files vary significantly by manufacturer — the .dvr extension is used by multiple proprietary systems, and some DVR formats embed non-standard codec parameters or use container wrappers that FFmpeg may not fully support. If FFmpeg reports an error reading your DVR file, the recording may use a proprietary variant that requires manufacturer-specific software for initial demuxing. The channel count and sample rate from the original DVR recording are preserved in the AU output, so stereo recordings remain stereo and the original sample rate (typically 44100 Hz or 48000 Hz for broadcast capture) is retained without resampling.