Convert AC3 to VOC — Free Online Tool
Convert AC3 (Dolby Digital) surround sound files to VOC format, transcoding the lossy multi-channel AC3 audio into uncompressed PCM unsigned 8-bit audio compatible with the classic Creative Labs Sound Blaster format. Ideal for retro game modding and DOS-era multimedia projects that require raw PCM audio in the legacy VOC container.
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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
AC3 is a lossy, compressed audio codec capable of carrying up to 5.1 surround sound channels at variable bitrates. VOC, by contrast, is a simple container developed by Creative Labs that stores raw uncompressed PCM audio — typically unsigned 8-bit mono or stereo. During this conversion, FFmpeg fully decodes the AC3 bitstream, which involves undoing Dolby Digital's perceptual compression and reconstructing the PCM waveform. The resulting audio is then downmixed from any surround channels to a stereo or mono signal (as VOC does not support multi-channel layouts) and encoded as pcm_u8 — unsigned 8-bit PCM — which is the VOC format's default and most compatible codec. Because pcm_u8 has very limited dynamic range (only 256 amplitude steps) compared to the 16-bit or 24-bit audio typical in AC3 sources, there will be a noticeable reduction in audio fidelity. The original AC3 file's lossy compression artifacts are also baked into the decoded signal before re-encoding.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary — the open-source multimedia processing engine that powers this conversion both in the browser (via FFmpeg.wasm) and on the desktop command line. |
-i input.ac3
|
Specifies the input file — in this case an AC3 (Dolby Digital) audio file. FFmpeg reads and fully decodes the compressed AC3 bitstream, reconstructing the raw audio waveform including any multi-channel surround information. |
-c:a pcm_u8
|
Sets the audio codec for the output to pcm_u8 — unsigned 8-bit raw PCM — which is the default and most broadly compatible audio encoding for the VOC format, matching the original Sound Blaster hardware's native audio format. |
output.voc
|
Defines the output filename with a .voc extension, which tells FFmpeg to write the result in the Creative Labs Voice File container format used by Sound Blaster cards and DOS-era games and applications. |
Common Use Cases
- Modding DOS-era games that load sound effects via VOC files, replacing original audio with remastered or custom Dolby Digital source material downconverted to the required format
- Preparing audio assets for vintage Sound Blaster card playback in retro computing environments where only the VOC format is natively supported
- Extracting a simplified PCM version of a Dolby Digital broadcast audio clip for use in a legacy multimedia authoring tool that only accepts VOC input
- Converting AC3 dialogue tracks from DVD rips into VOC files for use in fan-made tribute games or demoscene projects targeting DOS compatibility
- Building sound asset libraries for emulators or DOS sandbox environments where audio must be in VOC format to integrate with existing game engines
- Archiving a simplified, format-accurate version of AC3 audio in VOC for historical software preservation projects that must match original Sound Blaster-era specifications
Frequently Asked Questions
No. VOC is a legacy format designed for the Sound Blaster sound card and does not support multi-channel audio layouts like 5.1 surround. FFmpeg will automatically downmix the AC3's surround channels — center, LFE (subwoofer), and rear surrounds — into a stereo or mono signal during conversion. If you need to control how the downmix is performed, you can add FFmpeg's -ac flag (e.g., -ac 1 for mono or -ac 2 for stereo) before the output filename.
Significant quality reduction occurs at two stages. First, the AC3 source is already lossy, meaning Dolby Digital's perceptual compression has already discarded audio information. Second, pcm_u8 (unsigned 8-bit PCM) has a dynamic range of only about 48 dB — far less than the 16-bit audio (96 dB dynamic range) typical in AC3 sources — so the output will sound noticeably noisier and flatter, especially in quiet passages. The VOC format is fundamentally a low-fidelity legacy format and is not suitable for high-quality audio reproduction.
Yes. VOC supports both pcm_u8 and pcm_s16le (signed 16-bit little-endian PCM). Using pcm_s16le doubles the bit depth, giving you 96 dB of dynamic range instead of 48 dB, which results in significantly better audio fidelity. To do this, change the command to: ffmpeg -i input.ac3 -c:a pcm_s16le output.voc. Note that not all vintage Sound Blaster hardware or DOS software supports 16-bit VOC playback — pcm_u8 is the safest choice for maximum compatibility with original hardware.
AC3 is a compressed lossy format, so it stores audio in a compact bitstream — a typical 192k AC3 file uses far less space than raw audio. VOC with pcm_u8 stores audio as completely uncompressed raw samples, one byte per sample per channel. Even though 8-bit audio has lower fidelity, removing the compression means the file size is determined purely by duration and sample rate rather than a target bitrate. A one-minute AC3 file at 192 kbps (~1.4 MB) could expand to 5–10 MB or more as an uncompressed VOC file.
You can batch process files on the command line using a simple shell loop. On Linux or macOS, run: for f in *.ac3; do ffmpeg -i "$f" -c:a pcm_u8 "${f%.ac3}.voc"; done. On Windows Command Prompt, use: for %f in (*.ac3) do ffmpeg -i "%f" -c:a pcm_u8 "%~nf.voc". This applies the same pcm_u8 transcoding to every AC3 file in the current directory and outputs a corresponding VOC file for each. The browser-based tool on this page processes one file at a time.
No. The VOC format has virtually no metadata support — it was designed as a minimal container for raw Sound Blaster audio data, predating modern metadata standards entirely. Any embedded metadata in the AC3 source (such as Dolby Digital stream information, language tags, or dialnorm values) will be discarded during conversion. The resulting VOC file contains only the raw PCM audio samples and basic VOC header information like sample rate and bit depth.
Technical Notes
AC3 (Dolby Digital) supports bitrates from 32 kbps to 640 kbps and is inherently a lossy format using perceptual coding to discard frequencies less audible to the human ear. When FFmpeg decodes AC3, it reconstructs a floating-point PCM representation that approximates the original audio, but the lost information from the lossy encoding cannot be recovered. The VOC format, introduced with the Sound Blaster card in 1989, uses a simple chunked structure with a fixed header identifying it as a Creative Voice File. The default and most compatible audio codec for VOC is pcm_u8 — unsigned 8-bit PCM — where audio amplitude is stored as values from 0 to 255 (with 128 representing silence). This differs from the more common signed PCM formats (where 0 represents silence), and some modern audio tools may not handle VOC playback correctly without explicit format support. Sample rate is preserved from the source during conversion, though very high sample rates may not be compatible with all VOC players. Channel layout is a known limitation: VOC was designed for mono and stereo audio, so FFmpeg will automatically downmix AC3's potential 5.1 or 6-channel audio. No subtitle, chapter, or secondary audio track data applies to either format in this conversion.