Convert AVI to VOC — Free Online Tool
Convert AVI video files to VOC audio format, extracting the audio stream and encoding it as raw PCM data compatible with Creative Labs Sound Blaster hardware and DOS-era applications. The conversion discards the video track entirely and outputs uncompressed 8-bit unsigned PCM audio in the classic 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
AVI files store synchronized audio and video streams in an interleaved container, with audio typically encoded as MP3 (libmp3lame) or AAC. During this conversion, FFmpeg reads the AVI container, discards the video stream entirely, decodes the audio stream from whatever codec it uses, and then re-encodes it as pcm_u8 — unsigned 8-bit PCM at the original sample rate. The result is written into a VOC container, the proprietary format developed by Creative Labs for the Sound Blaster card. Because VOC supports only a single audio track, if the source AVI contains multiple audio tracks, only the first (default) track is extracted. The VOC format has no concept of bitrate-based compression — audio quality is determined purely by sample rate and bit depth, both of which are fixed at 8-bit unsigned PCM in the default output.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary — the underlying engine that powers this browser-based tool via its WebAssembly build (FFmpeg.wasm). The same command runs identically on a desktop FFmpeg installation for files over 1GB. |
-i input.avi
|
Specifies the input file as an AVI container. FFmpeg reads the AVI's interleaved audio and video streams, parses the AVI index, and makes all streams available for mapping or automatic selection. |
-c:a pcm_u8
|
Sets the audio codec to pcm_u8 — unsigned 8-bit pulse-code modulation — which is the default and most broadly compatible audio encoding for the VOC format. The source audio (typically MP3 or AAC from the AVI) is fully decoded and then re-encoded to raw 8-bit unsigned PCM samples, as expected by Sound Blaster hardware and DOSBox. |
output.voc
|
Defines the output filename with the .voc extension, which causes FFmpeg to select the VOC muxer automatically. The VOC muxer writes the Creative Labs file header and wraps the pcm_u8 audio data in the VOC block structure. The video stream from the AVI is implicitly dropped because the VOC format has no video support. |
Common Use Cases
- Supplying audio assets to retro DOS game mods or fan-made games that require Sound Blaster-compatible VOC files for their sound engines
- Archiving audio segments from legacy AVI recordings into VOC format for playback on period-accurate DOS hardware or emulators like DOSBox
- Extracting dialogue or sound effects from old AVI demo reels to reuse them in vintage multimedia authoring tools that only accept VOC input
- Converting AVI-stored tutorial recordings into VOC files for use with early 1990s multimedia kiosks or educational CD-ROM software that reads VOC audio
- Preparing audio samples from AVI footage for use with Sound Blaster-based hardware samplers or trackers that import VOC files natively
- Stripping and converting AVI audio to VOC as part of a retro game preservation workflow, ensuring compatibility with original DOS game engines
Frequently Asked Questions
Yes, there will be a significant reduction in audio fidelity. VOC with pcm_u8 encoding stores audio as 8-bit unsigned PCM, which provides only 256 discrete amplitude levels and a dynamic range of roughly 48 dB. By comparison, the MP3 or AAC audio in a typical AVI file is decoded at 16-bit precision before being downconverted. The 8-bit depth introduces audible quantization noise and a noticeable reduction in clarity, which is inherent to the VOC format's design for Sound Blaster hardware. If your target application supports it, switching the codec to pcm_s16le will produce 16-bit signed PCM with significantly better fidelity.
Yes. The VOC format supports both pcm_u8 and pcm_s16le codecs. To use 16-bit signed PCM, change the command to: ffmpeg -i input.avi -c:a pcm_s16le output.voc. This doubles the bit depth, yielding a dynamic range of approximately 96 dB and dramatically reducing quantization distortion. However, note that some older DOS applications and Sound Blaster drivers only support 8-bit VOC playback, so check your target application's compatibility before switching.
The video track is completely dropped. FFmpeg detects that the VOC container has no video codec support, so it automatically omits any video streams from the output. You do not need to explicitly pass a -vn flag because the VOC format specification itself prevents video from being written. Only the first audio stream from the AVI file is extracted and re-encoded into the VOC output.
No. The VOC format is a minimal, hardware-oriented audio container with no support for embedded metadata tags. Any title, artist, copyright, or comment metadata stored in the AVI file's header will be silently discarded during conversion. The VOC file contains only the raw audio data blocks and a basic header describing the codec, sample rate, and channel count.
You can adapt the displayed command into a shell loop for batch processing on your desktop. On Linux or macOS, run: for f in *.avi; do ffmpeg -i "$f" -c:a pcm_u8 "${f%.avi}.voc"; done. On Windows Command Prompt, use: for %f in (*.avi) do ffmpeg -i "%f" -c:a pcm_u8 "%~nf.voc". Each AVI file in the current directory will be processed in sequence, producing a matching VOC file. The browser-based tool processes one file at a time, so the FFmpeg command is especially valuable for bulk workflows.
Yes, DOSBox has native VOC playback support through its emulated Sound Blaster hardware, and files encoded with pcm_u8 are fully compatible. If you are embedding the VOC file into a DOS game that calls it via the Sound Blaster driver directly, ensure the sample rate of the output matches what the game engine expects — many DOS games assume 8000 Hz or 11025 Hz. You can add -ar 11025 to the FFmpeg command to resample the audio to 11025 Hz before writing the VOC file.
Technical Notes
The VOC format was designed specifically for Creative Labs Sound Blaster ISA cards in the late 1980s and early 1990s, and its structure reflects that era's hardware constraints. A VOC file begins with a 26-byte file header containing a magic string ('Creative Voice File'), followed by a series of typed data blocks. The audio data block carries the codec identifier, sample rate, and raw PCM samples. The pcm_u8 codec stores samples as unsigned bytes centered at 128 (silence), while pcm_s16le stores them as signed 16-bit little-endian integers. The VOC container does not support stereo audio in all block versions — FFmpeg will handle channel downmixing automatically if the source AVI contains stereo or surround audio. Because the AVI source may use a variable-bitrate compressed codec like MP3 or AAC, FFmpeg must fully decode the audio before re-encoding to PCM, meaning this is always a transcode (not a remux). File size of the resulting VOC will typically be larger than the AVI's audio portion because raw PCM is uncompressed, though the 8-bit depth keeps it smaller than 16-bit PCM would be. There is no support for subtitles, chapters, or multiple audio tracks in VOC output.