Extract Audio from FLV to VOC — Free Online Tool
Extract audio from FLV video files and save it as a VOC file — the classic Sound Blaster format used in DOS-era games and multimedia. The conversion decodes AAC or MP3 audio from the FLV container and re-encodes it as uncompressed 8-bit PCM, producing a VOC file that is fully compatible with vintage Sound Blaster hardware, DOSBox, and retro game engines.
to
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
FLV files typically carry AAC or MP3 audio streams wrapped in Adobe's Flash container format. During this conversion, FFmpeg strips the video stream entirely and decodes the compressed audio, then re-encodes it as unsigned 8-bit PCM (pcm_u8) — the native sample format of the Creative Labs VOC container. Because 8-bit PCM is a much simpler and lower-fidelity format than AAC or MP3, the process involves lossy quality reduction: dynamic range is compressed to 256 amplitude levels, and the result is raw, uncompressed audio in the VOC structure. The output file will generally be larger than the FLV's audio stream despite lower quality, because there is no compression applied — every sample is stored as a raw byte.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, which handles all decoding, stream selection, and re-encoding. In the browser, this runs via FFmpeg.wasm compiled to WebAssembly — no installation required. |
-i input.flv
|
Specifies the input FLV file. FFmpeg reads the Flash Video container, identifies the video and audio streams (typically H.264 video with AAC or MP3 audio), and makes them available for processing. |
-vn
|
Disables video output entirely, discarding the H.264 or FLV video stream from the FLV file. Since VOC is a pure audio format with no video support, this flag is required to produce a valid output. |
-c:a pcm_u8
|
Encodes the audio stream as unsigned 8-bit PCM — the native and most compatible audio codec for the VOC format. This decodes the FLV's compressed AAC or MP3 audio and converts it to raw 8-bit samples, matching the original Sound Blaster playback format used in DOS games. |
output.voc
|
Sets the output filename and tells FFmpeg to write a VOC container. FFmpeg detects the VOC format from the .voc extension and applies the correct file header, including the 'Creative Voice File' signature required for compatibility with Sound Blaster drivers and DOSBox. |
Common Use Cases
- Preparing custom music or voice lines extracted from FLV recordings for use in a DOS game mod or Sound Blaster-compatible retro project
- Converting FLV tutorial or gameplay recordings into VOC audio clips for playback inside DOSBox or a vintage DOS application
- Extracting narration or dialogue from an old Flash presentation saved as FLV to repurpose it as a VOC sound effect in a retro demoscene production
- Creating Sound Blaster-compatible audio assets from FLV source footage for use in a fan-made sequel or restoration of a 1990s DOS game
- Archiving the audio track of a Flash-era FLV video into a historically authentic format alongside other DOS multimedia artifacts
- Testing how modern audio content sounds when downsampled to 8-bit PCM to simulate the acoustic character of early Sound Blaster playback
Frequently Asked Questions
Yes — the quality reduction is significant and audible. FLV files typically contain AAC or MP3 audio encoded at 128 kbps or higher with 16-bit or 24-bit depth, while the default VOC output uses unsigned 8-bit PCM (pcm_u8), which supports only 256 amplitude levels. This produces a characteristic grainy or 'crunchy' sound reminiscent of early 1990s PC audio. If you need higher fidelity within the VOC format, you can switch the codec to pcm_s16le for 16-bit output, though VOC support for 16-bit is less universally compatible with vintage hardware and software.
Yes, VOC files encoded with pcm_u8 are the most compatible format for both DOSBox and real Creative Labs Sound Blaster hardware. The unsigned 8-bit PCM format is exactly what the original Sound Blaster 1.0 and 2.0 cards were designed to play. DOSBox emulates the Sound Blaster and handles VOC files natively through its built-in audio subsystem, making these files ideal for custom sound replacement in DOS games.
Despite being lower quality, VOC files with pcm_u8 audio are uncompressed — every audio sample is stored as a raw byte with no encoding or compression applied. FLV files, by contrast, use AAC or MP3 compression, which can reduce audio data to a fraction of its raw size. For example, one minute of mono audio at 22050 Hz stored as pcm_u8 requires about 1.3 MB, while the equivalent AAC stream in an FLV might occupy only 200–400 KB. The VOC container adds minimal overhead beyond the raw PCM data.
No. The VOC format has extremely limited metadata support by modern standards — it was designed for raw sound playback in DOS environments, not for tagging. FFmpeg will not transfer any ID3, XMP, or FLV metadata tags to the VOC output. If preserving metadata matters, you should store it separately or use a different output format such as FLAC or WAV that supports embedded tags.
Replace pcm_u8 with pcm_s16le in the command: ffmpeg -i input.flv -vn -c:a pcm_s16le output.voc. This encodes the audio as signed 16-bit little-endian PCM, which delivers significantly better dynamic range and fidelity. However, not all vintage DOS software and Sound Blaster drivers support 16-bit VOC playback — Sound Blaster Pro and later cards (SB16 and above) are required for hardware playback of 16-bit VOC files.
Yes. On Linux or macOS, you can use a shell loop: for f in *.flv; do ffmpeg -i "$f" -vn -c:a pcm_u8 "${f%.flv}.voc"; done. On Windows Command Prompt, use: for %f in (*.flv) do ffmpeg -i "%f" -vn -c:a pcm_u8 "%~nf.voc". This processes every FLV in the current directory and saves a matching VOC file. The browser-based tool handles one file at a time, so the FFmpeg command is the recommended approach for bulk conversion.
Technical Notes
The VOC format was introduced by Creative Labs in 1989 alongside the original Sound Blaster card and became a standard for digital audio in DOS gaming through the early 1990s. It supports a simple block-based structure containing raw PCM data, with optional loop and silence markers used by game engines. FFmpeg's VOC muxer implements the core audio data block and correctly writes the VOC header signature ('Creative Voice File'). The default pcm_u8 codec maps audio amplitude to values 0–255, with silence represented as 128 — a format quirk that differs from the signed convention used in most modern PCM audio. The sample rate of the output will be inherited from the FLV's audio stream; if your FLV contains audio at 44100 Hz or 48000 Hz, the VOC will retain that rate, though many vintage VOC players and DOS sound drivers only support rates up to 22050 Hz. You may wish to add -ar 22050 to the FFmpeg command for maximum compatibility with retro software. No subtitle, chapter, or multi-track audio features from the FLV are applicable here, as VOC supports only a single mono or stereo audio stream.