Extract Audio from M4V to VOC — Free Online Tool
Extract audio from M4V video files and save it as VOC format — the classic Creative Labs Sound Blaster audio container. This tool demuxes the AAC audio track from your M4V and re-encodes it to raw unsigned 8-bit PCM, the native encoding used by VOC files in DOS-era multimedia and game audio.
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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
M4V files typically carry AAC-encoded audio inside an MPEG-4 container. Because VOC is a raw PCM format with no support for compressed audio codecs like AAC, the audio must be fully decoded and then re-encoded as uncompressed PCM. This tool uses the pcm_u8 codec, which produces unsigned 8-bit PCM audio at the target sample rate — the standard data format for Creative Labs VOC files. The video stream is discarded entirely using the -vn flag. The result is a lossless PCM representation of your audio, though the 8-bit depth means the dynamic range is limited to approximately 48 dB, which is characteristic of the VOC format's original hardware constraints.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In this browser-based tool, this runs via FFmpeg.wasm compiled to WebAssembly — the same command works identically on your local desktop installation of FFmpeg. |
-i input.m4v
|
Specifies the input file — your M4V video, which typically contains a libx264 or libx265 video stream and an AAC audio stream inside an MPEG-4 container. |
-vn
|
Disables video output entirely, discarding the H.264 or H.265 video stream from the M4V. VOC is a pure audio format with no video support, so this flag is required. |
-c:a pcm_u8
|
Encodes the audio as unsigned 8-bit PCM — the native codec for classic Creative Labs VOC files. This decodes the AAC audio from the M4V and re-encodes it as raw uncompressed 8-bit samples, which is required because VOC cannot store compressed audio codecs like AAC. |
output.voc
|
Sets the output filename with the .voc extension, which tells FFmpeg to use the VOC muxer and produce a Creative Labs Sound Blaster-compatible audio file containing the pcm_u8 audio stream. |
Common Use Cases
- Extracting audio from iTunes M4V video downloads to use as sound effects or music in a DOS game or retro game mod that requires VOC format assets
- Preparing audio samples from M4V-encoded Apple TV or iOS content for playback through DOSBox, which natively supports VOC files for Sound Blaster emulation
- Converting M4V video commentary or narration tracks into VOC files for use with legacy multimedia authoring tools that only accept Creative Labs audio formats
- Archiving or restoring period-accurate audio assets — for example, extracting music from an M4V recording of a retro-gaming session and re-encoding it in the era-correct VOC container
- Building a Sound Blaster-compatible audio library from M4V source material for use in homebrew DOS software development or demoscene projects
Frequently Asked Questions
Yes, there will be a quality reduction. Your M4V file's AAC audio is first decoded to PCM (lossless at that stage), but then stored as unsigned 8-bit PCM in the VOC file. 8-bit PCM has a dynamic range of only about 48 dB and a maximum sample resolution of 256 steps, compared to the 16-bit or 24-bit audio you may be used to. For retro gaming and DOS compatibility purposes this is expected and intentional, but it is not suitable for high-fidelity audio archiving.
VOC format support for stereo depends on the version of the VOC specification. FFmpeg's VOC muxer supports stereo output, but many legacy Sound Blaster applications and DOS programs only expect mono VOC files. If you encounter compatibility issues with your target application, you can add -ac 1 to the FFmpeg command to downmix the stereo AAC audio from your M4V to a single mono channel before encoding to pcm_u8.
Yes. The VOC format does support 16-bit signed little-endian PCM (pcm_s16le), which provides significantly better dynamic range — approximately 96 dB versus 48 dB for 8-bit. You can change the command to ffmpeg -i input.m4v -vn -c:a pcm_s16le output.voc to use 16-bit encoding. However, note that some legacy DOS applications and Sound Blaster hardware emulators only support 8-bit VOC playback, so check your target environment before switching.
Both are lost. VOC is an extremely minimal audio format with no support for chapters, metadata, or multiple tracks — it contains only a raw audio data stream. Only the first (default) audio track from your M4V will be extracted and encoded. If your M4V contains multiple language tracks or a separate commentary track you want to preserve, you would need to run separate FFmpeg commands using the -map flag to select each track individually before converting to VOC.
FFmpeg does not natively batch process files in a single command, but you can use a shell loop. On Linux or macOS, run: for f in *.m4v; do ffmpeg -i "$f" -vn -c:a pcm_u8 "${f%.m4v}.voc"; done. On Windows Command Prompt, use: for %f in (*.m4v) do ffmpeg -i "%f" -vn -c:a pcm_u8 "%~nf.voc". This will process each M4V in the current directory and output a corresponding VOC file.
The M4V file stores audio as AAC, which is a compressed lossy codec that typically achieves 5:1 to 10:1 compression ratios. VOC with pcm_u8 stores raw uncompressed audio samples — every second of audio takes (sample rate × channels) bytes of space. For example, a 44100 Hz mono stream uses about 44 KB per second. This is fundamentally how uncompressed PCM formats work, and the file size increase compared to AAC is expected and normal.
Technical Notes
VOC is one of the oldest standardized audio container formats still in active use for retro computing, developed by Creative Labs in the early 1990s for the Sound Blaster ISA card. Its structure consists of a file header followed by typed data blocks, which is why FFmpeg can mux it cleanly but the format itself carries almost no metadata — no title, no artist tags, no sample rate negotiation beyond what is embedded in the block headers. When converting from M4V, the AAC audio codec must be fully decoded by FFmpeg before re-encoding as pcm_u8, making this a transcode rather than a remux. The unsigned 8-bit PCM encoding means sample values range from 0 to 255, with silence at 128 — not at 0 as with signed PCM formats like pcm_s16le. This representation is important to understand if you plan to process the VOC file programmatically. M4V files may carry DRM protection (FairPlay) applied by Apple; if your M4V is DRM-protected, FFmpeg will not be able to read the audio stream and the conversion will fail regardless of the output format chosen.