Convert WebM to VOC — Free Online Tool
Convert WebM video files to VOC audio format, extracting the audio stream and encoding it as raw unsigned 8-bit PCM — the native format for Creative Labs Sound Blaster cards and classic DOS multimedia. This tool strips the VP9 video and Opus/Vorbis audio, re-encoding only the audio to uncompressed PCM_U8 compatible with legacy VOC players and retro game engines.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your WebM file here
or click to browse
Free — no uploads, no signups. Your files never leave your browser.
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
WebM is a modern container holding compressed video (VP9) and compressed audio (Opus or Vorbis). VOC, by contrast, is a purely audio format with no video support, designed to store raw PCM audio for early Sound Blaster hardware. During this conversion, the video stream is completely discarded — VOC has no mechanism to carry video data. The Opus or Vorbis audio stream is then decoded from its compressed form and re-encoded as unsigned 8-bit PCM (pcm_u8), which is the default and most compatible codec for VOC files. This is a lossy-to-lossless conversion in terms of codec type, but 8-bit PCM has a very limited dynamic range (only 256 amplitude levels), so the output will have noticeably lower fidelity than the source Opus audio. Sample rate is preserved from the input unless explicitly overridden. The resulting VOC file will be significantly larger per second of audio than the WebM source, because PCM stores every sample uncompressed.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg command-line tool, the engine powering this conversion both in your browser (via FFmpeg.wasm) and on your local desktop. |
-i input.webm
|
Specifies the input WebM file, which may contain a VP9 video stream alongside Opus or Vorbis compressed audio — both of which FFmpeg will decode as needed. |
-c:a pcm_u8
|
Sets the audio codec to unsigned 8-bit PCM, the native and most compatible audio encoding for the VOC format, matching what Creative Labs Sound Blaster hardware originally used for playback. |
output.voc
|
Defines the output file name and triggers VOC container muxing. FFmpeg infers the VOC format from the .voc extension, automatically discarding the WebM's video stream since VOC is audio-only. |
Common Use Cases
- Preparing audio assets extracted from WebM web recordings for use in a DOS game engine or retro game modding project that requires VOC format sound effects
- Converting a WebM tutorial or explainer video's audio track into a VOC file for playback on a vintage PC with a Sound Blaster card or DOSBox emulator
- Extracting narration or dialog audio from a WebM file to use as VOC voice clips in a classic game like Doom, Quake, or a ScummVM-compatible adventure game
- Archiving web-sourced WebM audio into the VOC format for a retro computing museum or preservation project that catalogues Sound Blaster-era media
- Generating VOC sound files from modern WebM recordings for use in homebrew DOS software, demos, or chiptune/oldschool multimedia productions
Frequently Asked Questions
Yes, significantly. The Opus or Vorbis audio in a WebM file is a modern compressed codec capable of high fidelity at low bitrates. When re-encoded to pcm_u8 (unsigned 8-bit PCM), the audio is limited to only 256 possible amplitude levels, which results in audible quantization noise and a muffled, lo-fi character. This is an inherent limitation of the VOC format's 8-bit depth, not a flaw in the conversion process — it matches what original Sound Blaster hardware actually played back.
The VP9 video stream is completely dropped. VOC is a pure audio format with no container structure for video, subtitles, chapters, or metadata — it can only hold a single PCM audio stream. FFmpeg automatically handles this by selecting only the audio stream when the output format cannot accept video.
Yes. The VOC format also supports 16-bit signed little-endian PCM (pcm_s16le), which provides 65,536 amplitude levels and dramatically better dynamic range. To use it, modify the command to: ffmpeg -i input.webm -c:a pcm_s16le output.voc. This is recommended whenever the VOC file will be played back on software or emulators that support 16-bit VOC, such as DOSBox.
Add the -ar flag followed by your desired sample rate in Hz. For example, to resample to 22050 Hz — a common rate for Sound Blaster VOC files — use: ffmpeg -i input.webm -c:a pcm_u8 -ar 22050 output.voc. Original Sound Blaster hardware and many DOS games used 8000–22050 Hz, so resampling down can improve compatibility with authentic retro playback environments.
Yes, using a shell loop. On Linux or macOS: for f in *.webm; do ffmpeg -i "$f" -c:a pcm_u8 "${f%.webm}.voc"; done. On Windows Command Prompt: for %f in (*.webm) do ffmpeg -i "%f" -c:a pcm_u8 "%~nf.voc". This processes every WebM file in the current directory, outputting a matching VOC file for each.
No. The VOC format has no metadata support whatsoever — it is a raw audio container with only a minimal header describing the audio format, sample rate, and bit depth. Any tags, chapter markers, or additional audio tracks present in the WebM file will be silently discarded during conversion.
Technical Notes
VOC files use a simple block-based structure designed for the Sound Blaster ISA card's DMA audio playback. The format supports only a single mono or stereo audio stream encoded as either unsigned 8-bit or signed 16-bit little-endian PCM. When converting from WebM, FFmpeg decodes the Opus or Vorbis stream to raw PCM internally, then encodes it to pcm_u8 — the VOC default. Because pcm_u8 represents audio samples as values from 0–255 with 128 as silence (rather than the signed -32768 to 32767 of 16-bit PCM), the dynamic range is only 48 dB, compared to roughly 96 dB for 16-bit audio. WebM files that contain multiple audio tracks will have only the first (default) audio track converted, as VOC cannot hold multiple streams. Transparency, subtitles, and HDR metadata — all features supported by WebM — are irrelevant to VOC and are dropped entirely. Output file sizes will be substantially larger than the WebM source: a 1-minute mono 22050 Hz pcm_u8 VOC file is approximately 1.3 MB, whereas a comparable WebM with Opus audio might be under 100 KB. There is no quality parameter available for raw PCM codecs; quality is determined entirely by bit depth (-c:a pcm_u8 vs pcm_s16le) and sample rate (-ar).