Extract Audio from RMVB to VOC — Free Online Tool
Extract audio from RMVB video files and save it as VOC format — a raw PCM audio container developed by Creative Labs for the Sound Blaster era. The audio is decoded from AAC or MP3 and re-encoded as uncompressed 8-bit unsigned PCM (pcm_u8), producing a lossless VOC file compatible with DOS-era tools and retro gaming environments.
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FFmpeg Command
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Estimated output:
Conversion Complete!
DownloadHow It Works
RMVB files use a variable-bitrate RealMedia container that typically carries AAC or MP3-compressed audio streams. During this conversion, FFmpeg demuxes the RMVB container, strips the video stream entirely, decodes the compressed audio to raw PCM in memory, and then re-encodes it as 8-bit unsigned PCM (pcm_u8) wrapped in the VOC container format. Because VOC only supports raw PCM codecs and not AAC or MP3 natively, a full decode-and-re-encode of the audio is required — the audio stream cannot be stream-copied. The resulting VOC file is uncompressed, meaning it will typically be significantly larger than the audio track inside the source RMVB, but it will be free of any lossy codec artifacts beyond those already introduced by the original RMVB encoding.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, which handles the entire pipeline: demuxing the RMVB container, decoding the compressed audio stream, and re-encoding and muxing the output VOC file. |
-i input.rmvb
|
Specifies the source RMVB file as input. FFmpeg's RealMedia demuxer reads the variable-bitrate container and exposes the contained video and audio streams (typically H.264 video and AAC or MP3 audio) for processing. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore the video stream from the RMVB file. Since VOC is a pure audio format with no video support, this flag is required to produce a valid output file. |
-c:a pcm_u8
|
Sets the audio codec to 8-bit unsigned PCM, the default and most broadly compatible codec for the VOC format. Because the RMVB source uses a compressed codec (AAC or MP3) that VOC cannot store natively, FFmpeg fully decodes the audio and re-encodes it as raw uncompressed pcm_u8 samples. |
output.voc
|
Specifies the output filename and tells FFmpeg to use the Creative Labs VOC muxer based on the .voc extension, producing a file that is directly compatible with DOSBox, Sound Blaster emulators, and legacy DOS audio tools. |
Common Use Cases
- Extracting dialogue or sound effects from an RMVB anime or movie file to use as audio samples in a DOS-compatible retro game or demoscene project
- Preparing audio assets from RMVB source material for use with Sound Blaster-compatible emulators such as DOSBox, which natively support VOC playback
- Converting RMVB-encoded audio tracks to raw PCM VOC files for analysis or editing in legacy audio tools that only accept the Creative Labs VOC format
- Archiving the audio track of an RMVB video as an uncompressed VOC file to eliminate lossy codec dependency for long-term audio preservation of the raw sample data
- Extracting background music or narration from an RMVB educational or multimedia CD-ROM rip to rebuild a retro-style application that uses VOC audio assets
Frequently Asked Questions
The VOC file itself uses uncompressed pcm_u8 audio, which is lossless at the PCM level, but there is one unavoidable quality concern: the audio inside the RMVB is already lossy-compressed (typically as AAC at 128k or MP3). That lossy compression cannot be undone — the conversion decodes what is there and stores it as raw PCM. Additionally, pcm_u8 uses 8-bit unsigned samples, which has a relatively low dynamic range compared to 16-bit PCM, so very quiet or highly dynamic audio may show some quantization noise compared to the source. If preserving maximum fidelity matters more than DOS compatibility, consider using pcm_s16le instead.
RMVB stores audio in a compressed lossy format like AAC or MP3, which achieves very high compression ratios. VOC stores audio as raw uncompressed PCM bytes with no compression whatsoever. A 128kbps AAC stream in an RMVB file might become 8 to 10 times larger when written out as uncompressed pcm_u8 in a VOC file, because every audio sample is stored as a raw byte rather than an encoded bitstream. This is expected behavior and is inherent to the lossless, uncompressed nature of the VOC format.
Yes. DOSBox has native support for the Creative Labs VOC format, and files containing pcm_u8 audio are the most broadly compatible variant for DOS-era Sound Blaster emulation. Many classic DOS games used VOC files with 8-bit unsigned PCM at sample rates ranging from 8kHz to 44.1kHz, so a VOC file produced by this tool should play back correctly in DOSBox without any additional conversion steps.
FFmpeg will preserve the original sample rate from the audio track inside the RMVB file unless you explicitly specify a different rate. Most RMVB files carry audio at 44100 Hz or 48000 Hz. The VOC format supports a range of sample rates, but if you need a specific rate for compatibility with a DOS application or emulator (for example, 22050 Hz), you can add '-ar 22050' to the FFmpeg command before the output filename.
Replace '-c:a pcm_u8' with '-c:a pcm_s16le' in the command to produce 16-bit signed little-endian PCM audio inside the VOC container. This doubles the file size compared to pcm_u8 but significantly increases dynamic range and reduces quantization noise, making it a better choice when the source RMVB audio was encoded at a higher bitrate and you want to preserve as much of that quality as the uncompressed format allows. The full command would be: ffmpeg -i input.rmvb -vn -c:a pcm_s16le output.voc
Yes. On Linux or macOS, you can run a shell loop such as: for f in *.rmvb; do ffmpeg -i "$f" -vn -c:a pcm_u8 "${f%.rmvb}.voc"; done. On Windows Command Prompt, use: for %f in (*.rmvb) do ffmpeg -i "%f" -vn -c:a pcm_u8 "%~nf.voc". This will process every RMVB file in the current directory and produce a matching VOC file for each one, which is useful if you are converting a full collection of RMVB-encoded episodes or multimedia discs.
Technical Notes
The VOC format was designed in the early 1990s for the Creative Labs Sound Blaster card and has almost no modern adoption outside of retro computing and DOS emulation contexts. It supports only raw PCM audio — specifically pcm_u8 (8-bit unsigned) and pcm_s16le (16-bit signed little-endian) — and carries no metadata such as title, artist, or album tags, none of which can be preserved from the RMVB source. RMVB itself also has limited metadata support, so this is rarely a practical loss. The VOC container does not support multiple audio tracks, stereo interleaving beyond basic two-channel PCM, or any form of compression. Because RMVB uses variable bitrate encoding for both its video and audio streams, the audio duration can be confirmed by FFmpeg's demuxer but the bitrate reported in RMVB headers may be approximate. One important compatibility note: some older VOC-reading applications and DOS programs expect specific sample rates (particularly 8000, 11025, 22050, or 44100 Hz) and may not handle arbitrary rates correctly, so if your target environment is strict, add an explicit '-ar' flag to resample during conversion.