Convert WMV to VOC — Free Online Tool
Convert WMV video files to VOC audio format, extracting the audio stream and encoding it as uncompressed PCM data compatible with Creative Labs Sound Blaster hardware and DOS-era applications. The conversion strips all video content and re-encodes audio to unsigned 8-bit PCM (pcm_u8), the native codec of the VOC container.
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FFmpeg Command
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Estimated output:
Conversion Complete!
DownloadHow It Works
WMV files store audio using WMA (Windows Media Audio, typically wmav2) inside an ASF container alongside a video stream encoded with Microsoft MPEG-4 variants. During this conversion, FFmpeg discards the video stream entirely and decodes the WMA audio, then re-encodes it as unsigned 8-bit PCM at the original sample rate. The output is wrapped in a VOC container — a simple, header-driven format developed by Creative Labs that stores raw PCM blocks with minimal metadata. Because WMA is a lossy compressed format and PCM is uncompressed, the output VOC file represents the decoded audio fidelity of the WMV source without any additional compression artifacts, though the original quality ceiling is set by the WMV's lossy encoding.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which handles the full pipeline of demuxing the WMV/ASF container, decoding the WMA audio stream, and re-encoding and muxing the output into a VOC file. |
-i input.wmv
|
Specifies the source WMV file. FFmpeg automatically detects the ASF container and identifies the audio (typically wmav2) and video (typically msmpeg4) streams inside it. |
-c:a pcm_u8
|
Sets the audio codec to unsigned 8-bit PCM, the native and default audio encoding of the VOC format. This decodes the lossy WMA audio from the WMV and re-encodes it as raw, uncompressed 8-bit samples compatible with Creative Labs Sound Blaster hardware and DOS applications. |
output.voc
|
Defines the output filename and triggers FFmpeg to use the VOC muxer based on the .voc file extension. No video stream is written because VOC is an audio-only format, so the Microsoft MPEG-4 video from the WMV source is automatically dropped. |
Common Use Cases
- Extracting dialogue or sound effects from old Windows Media Video tutorials or presentations for use in a DOS-based game engine that requires VOC audio assets
- Porting audio from WMV-format archival recordings of early 2000s multimedia content into retro computing projects that run on DOSBox or real DOS hardware
- Converting WMV-encoded narration or voice lines into VOC format for use with Sound Blaster-compatible audio playback libraries in homebrew software
- Pulling audio from WMV screen recordings to create raw PCM sound samples usable in vintage demoscene or chiptune production tools that accept VOC input
- Archiving audio from WMV media files in an uncompressed, historically authentic format for retro gaming preservation projects or museum exhibits featuring Sound Blaster hardware
- Preparing audio assets from Windows Media Video content for integration into legacy educational software or CD-ROM game titles being restored or remastered
Frequently Asked Questions
The WMV source already contains lossy-compressed WMA audio, so the quality ceiling of your output is already determined before conversion begins. The VOC file will use uncompressed pcm_u8 (unsigned 8-bit PCM), which means no further compression artifacts are introduced during re-encoding. However, 8-bit PCM has a dynamic range of only about 48 dB, which is significantly lower than modern audio standards, so the output may sound noisier or more limited than the original WMV audio if that audio was encoded at higher bit depths.
The primary reason is the bit depth reduction: pcm_u8 encodes audio at 8 bits per sample, which is the native format for VOC files and Sound Blaster hardware. WMA audio in WMV files is typically decoded to 16-bit or higher internal precision before being re-encoded to 8-bit unsigned PCM. This downward conversion reduces dynamic range and can introduce audible quantization noise, particularly noticeable in quiet passages. If you need higher fidelity, the pcm_s16le codec is also supported by the VOC format and can be specified manually in the FFmpeg command.
No. The VOC format was designed for Sound Blaster hardware in the DOS era and has virtually no metadata support — it stores audio blocks and basic header information such as sample rate and codec type, but no ID3-style tags or ASF metadata fields. Any title, author, copyright, or description information embedded in the WMV's ASF container will be silently discarded during conversion.
Replace pcm_u8 with pcm_s16le in the command: ffmpeg -i input.wmv -c:a pcm_s16le output.voc. The pcm_s16le codec uses signed 16-bit little-endian PCM, which offers significantly better dynamic range (about 96 dB versus 48 dB for 8-bit) and is also supported by the VOC container format. This is especially useful if your target application or Sound Blaster emulator supports 16-bit playback.
Yes. On Linux or macOS, you can use a shell loop: for f in *.wmv; do ffmpeg -i "$f" -c:a pcm_u8 "${f%.wmv}.voc"; done. On Windows Command Prompt, use: for %f in (*.wmv) do ffmpeg -i "%f" -c:a pcm_u8 "%~nf.voc". Each file is processed sequentially, and the video stream is discarded in every case. This is particularly useful when converting a folder of WMV game cutscenes or multimedia assets for a retro porting project.
The video stream — encoded in one of the Microsoft MPEG-4 variants (msmpeg4 or msmpeg4v2) — is completely discarded. FFmpeg extracts only the audio stream for re-encoding. The VOC format is audio-only and has no mechanism to store video data, so no video frames, thumbnails, or visual content of any kind are preserved in the output file.
Technical Notes
WMV files use the ASF (Advanced Systems Format) container, which requires the special -f asf flag when writing WMV output, though for reading this conversion handles it transparently. The audio in WMV is almost universally WMA version 2 (wmav2), a proprietary lossy codec that must be fully decoded before re-encoding to PCM — unlike some container conversions where audio can be stream-copied, this conversion always involves a full decode-and-re-encode cycle. The VOC format uses a block-based structure where audio data is stored in typed chunks; FFmpeg writes the pcm_u8 data into these blocks automatically. One important limitation is that VOC files do not support multiple audio tracks, so if the WMV source contains multiple audio streams (e.g., multiple language tracks), only the default or first audio stream will be extracted. Additionally, VOC has limited sample rate support tied to its Sound Blaster heritage — very high sample rates common in modern WMV files (e.g., 48000 Hz) may be written as-is into the VOC container, but playback compatibility on real or emulated Sound Blaster hardware may require resampling to rates like 22050 Hz or 44100 Hz. The absence of any audio quality parameters in the FFmpeg command reflects that PCM encoding has no quality knobs — fidelity is determined entirely by bit depth and sample rate.