Convert RMVB to VOC — Free Online Tool
Convert RMVB video files to VOC audio format, extracting the audio stream and encoding it as raw PCM (unsigned 8-bit) compatible with Creative Labs Sound Blaster hardware and DOS-era applications. This tool strips the RealMedia variable-bitrate video container entirely, delivering a retro-compatible audio file directly in your browser.
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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
RMVB files use RealNetworks' variable bitrate container, typically carrying compressed audio encoded as AAC or MP3 alongside a video stream. During this conversion, FFmpeg discards the video stream entirely and decodes the compressed audio track from the RMVB container. The decoded audio is then re-encoded as PCM unsigned 8-bit (pcm_u8), which is the native raw audio format used by Creative Labs VOC files. This is a two-step process: lossy decompression of the source audio (since RMVB audio is compressed), followed by lossless writing of the resulting raw PCM samples into the VOC container structure. The output will be significantly larger than the source audio track because PCM stores uncompressed sample data, and the 8-bit unsigned format limits dynamic range to 48 dB, which is a notable quality constraint compared to the source.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg command-line tool, which handles all reading, decoding, encoding, and writing operations for this RMVB-to-VOC conversion. |
-i input.rmvb
|
Specifies the input file in RealMedia Variable Bitrate format. FFmpeg parses the RMVB container to locate and demux the audio and video streams contained within it. |
-c:a pcm_u8
|
Sets the audio codec to PCM unsigned 8-bit, which is the native encoding format for classic Creative Labs VOC files. This decodes the compressed RMVB audio (AAC or MP3) and re-encodes it as raw 8-bit uncompressed samples, which the VOC container stores directly. |
output.voc
|
Defines the output filename with the .voc extension, which tells FFmpeg to write the result in the Creative Labs VOC container format. The video stream from the RMVB source is automatically discarded since VOC supports audio only. |
Common Use Cases
- Extracting dialogue or music from an RMVB anime or foreign film to load into a retro DOS game engine or sound tool that only accepts VOC files
- Preparing audio samples from RMVB video archives for playback on original Sound Blaster hardware or DOSBox emulation environments
- Converting RMVB-encoded cutscene audio for integration into classic game modding projects that use VOC format for in-game voice lines
- Archiving audio from legacy RMVB multimedia content into a raw PCM format for analysis or processing in vintage audio software
- Extracting the audio track from an RMVB lecture or presentation recording to create a simple, uncompressed audio file for use in retro computing demos or exhibitions
Frequently Asked Questions
Not fully. RMVB files store audio in a compressed lossy format (typically AAC or MP3), so the source audio has already undergone quality reduction. When converting to VOC with pcm_u8 (unsigned 8-bit PCM), FFmpeg decodes that compressed audio and then stores it as raw 8-bit samples. The 8-bit depth limits dynamic range to roughly 48 dB, which is noticeably lower fidelity than the original compressed audio. You will hear increased noise and reduced detail, particularly in quiet passages — this is a fundamental characteristic of the VOC format's 8-bit PCM encoding.
RMVB stores audio in a compressed format like AAC or MP3, which can reduce file size by 10x or more compared to raw audio. VOC files store uncompressed PCM samples — every millisecond of audio is written as raw byte values with no compression. Even though the pcm_u8 format uses only 1 byte per sample (the most compact PCM option available in VOC), the resulting file will still be substantially larger than the compressed audio it was decoded from.
The video stream is completely discarded. FFmpeg reads the RMVB container, selects only the audio track, and writes nothing from the video to the output. VOC is a pure audio format with no support for video data, so there is no way to preserve the visual content. If you need the video, you should keep the original RMVB file or convert it to a video-capable output format separately.
Yes. The VOC format supports both pcm_u8 (8-bit unsigned) and pcm_s16le (16-bit signed little-endian PCM). The 16-bit option provides 96 dB of dynamic range instead of 48 dB, significantly improving fidelity. To use it, run: ffmpeg -i input.rmvb -c:a pcm_s16le output.voc. Note that pcm_s16le compatibility may be more limited on very old Sound Blaster hardware or software that only supports 8-bit VOC playback.
On Linux or macOS, you can use a shell loop: for f in *.rmvb; do ffmpeg -i "$f" -c:a pcm_u8 "${f%.rmvb}.voc"; done. On Windows Command Prompt, use: for %f in (*.rmvb) do ffmpeg -i "%f" -c:a pcm_u8 "%~nf.voc". This processes each RMVB file in the current directory and outputs a matching VOC file. The browser-based tool handles one file at a time, so the command line approach is recommended for bulk conversions.
No. The VOC format does not support metadata fields such as title, artist, or album. Any metadata embedded in the RMVB container by RealNetworks tools will be silently dropped during conversion. If preserving metadata is important, you should consider a more modern lossless audio output format instead of VOC.
Technical Notes
The VOC format was designed in the early 1990s for Creative Labs Sound Blaster cards and has a simple block-based structure that supports raw PCM audio only. The default codec used here, pcm_u8, stores each audio sample as an unsigned 8-bit integer (values 0–255, with silence at 128). This format is mono or stereo but with severe dynamic range limitations. The RMVB source file's audio — typically encoded at 128 kbps AAC or similar — will be fully decoded before being quantized down to 8-bit depth, introducing quantization noise that is audible on any modern playback system. Sample rate is preserved from the source during conversion; however, very high sample rates (e.g., 48 kHz) in the RMVB audio will produce a larger VOC file and may not be supported by all legacy VOC players, which often expect 22050 Hz or 44100 Hz. FFmpeg does not apply dithering by default when reducing bit depth, which can make the quantization noise more perceptible — adding -af aresample=resampler=swr:dither_method=triangular before the output filename can improve perceived quality slightly. The VOC container does not support chapters, subtitle tracks, or multiple audio streams, none of which are relevant here since RMVB's secondary tracks are also dropped.