Extract Audio from VOB to WMA — Free Online Tool
Extract audio from VOB DVD files and convert it to WMA format, transcoding the AC3 (Dolby Digital) or other DVD audio streams into Windows Media Audio using the wmav2 codec. Ideal for pulling dialogue, music, or commentary tracks from DVD content into a format compatible with Windows Media Player and legacy Microsoft ecosystem software.
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FFmpeg Command
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Estimated output:
Conversion Complete!
DownloadHow It Works
VOB files contain multiplexed streams — typically MPEG-2 video, AC3 (Dolby Digital) audio, and optionally subtitles. This tool discards the video and subtitle streams entirely and extracts only the primary audio track. Because VOB's default AC3 audio cannot be placed directly into a WMA container, FFmpeg re-encodes the audio from AC3 into the wmav2 codec (Windows Media Audio v2), which is a lossy compression format developed by Microsoft. The result is a standalone .wma file containing only the re-encoded audio. This is a full transcode — not a remux — meaning some audio generation loss occurs as the signal passes from one lossy format (AC3) to another (WMA).
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which handles all demuxing, decoding, re-encoding, and muxing steps needed to pull audio out of a VOB and write it as a WMA file. |
-i input.vob
|
Specifies the source VOB file as input. FFmpeg will parse the MPEG-2 Program Stream structure to identify and separate the embedded video, audio, and subtitle streams contained inside. |
-vn
|
Disables video output entirely, instructing FFmpeg to ignore the MPEG-2 video stream in the VOB and produce an audio-only output file — essential for clean audio extraction. |
-c:a wmav2
|
Sets the audio encoder to wmav2 (Windows Media Audio version 2), Microsoft's standard lossy audio codec, which is required to write a valid WMA container file and provides better quality than the older wmav1 at the same bitrate. |
-b:a 128k
|
Sets the audio bitrate for the wmav2 encoder to 128 kilobits per second, a balance between file size and audio quality suitable for most speech and general audio content extracted from DVD VOB files. |
output.wma
|
Defines the output filename and triggers FFmpeg to use the ASF/WMA container format, which is the native container for Windows Media Audio codec streams. |
Common Use Cases
- Ripping the audio commentary track from a DVD movie to listen to director or cast commentary on a Windows device or media player that natively supports WMA
- Extracting a music concert DVD's audio into WMA for playback on older portable Windows Media-compatible devices like early Zune players or Windows CE devices
- Pulling dialogue or narration from a corporate training or educational DVD to archive as a WMA audio file for integration into a Windows-based e-learning system
- Converting a DVD audiobook disc (stored as VOB files) into WMA files for playback in Windows Media Player or Windows Media Center without needing the physical disc
- Extracting the audio from a VOB file ripped from a home movie DVD to create a smaller audio-only keepsake file in a format readily playable across Windows computers
Frequently Asked Questions
Yes, there will be some quality loss because this conversion involves transcoding from one lossy format to another. The AC3 audio in the VOB is already lossy Dolby Digital compression, and re-encoding it into wmav2 introduces a second generation of lossy compression. To minimize quality degradation, you can increase the WMA bitrate in the FFmpeg command from the default 128k to 192k or 256k, which gives the wmav2 encoder more data to work with and better preserves the original AC3 signal.
Not necessarily by default. AC3 in VOB files frequently carries 5.1 surround sound (six channels), while wmav2 can technically handle multiple channels but will default to stereo in most FFmpeg configurations unless you explicitly specify channel mapping. If preserving surround sound is important, you would need to add flags like '-ac 6' to the command to retain all six channels, though playback support for multi-channel WMA varies by player.
Yes. VOB files often contain multiple audio streams for different languages or commentary. By default FFmpeg selects the first audio stream, but you can target a specific track by adding '-map 0:a:1' (for the second audio track) or '-map 0:a:2' (for the third) to the command before the output filename. You can inspect which audio streams exist in your VOB file by running 'ffmpeg -i input.vob' in a terminal and reviewing the stream list.
Modify the '-b:a 128k' portion of the command to a higher value. For example, replacing it with '-b:a 256k' or '-b:a 320k' will produce a higher-quality WMA file at the cost of a larger file size. The wmav2 codec supports bitrates from 64k up to 320k. For typical speech content from a VOB, 128k is usually sufficient, but for music extracted from a concert DVD, 192k or higher is recommended.
VOB files use MPEG-2 program stream packaging which can include padding, timing offsets, and GOP-aligned audio that doesn't always start at exactly the same timestamp as expected. FFmpeg handles this during demuxing, but minor timing discrepancies at the start or end of the output WMA file can occasionally occur. If you notice a significant duration mismatch, adding '-async 1' to the command can help FFmpeg resync the audio timestamps during re-encoding.
Yes. On Windows, you can use a simple batch script: 'for %f in (*.vob) do ffmpeg -i "%f" -vn -c:a wmav2 -b:a 128k "%~nf.wma"'. On Linux or macOS, the equivalent shell command is 'for f in *.vob; do ffmpeg -i "$f" -vn -c:a wmav2 -b:a 128k "${f%.vob}.wma"; done'. This loops through every VOB file in the current directory and produces a matching WMA file for each one, which is particularly useful when dealing with a multi-episode DVD rip split across several VOB files.
Technical Notes
VOB is an MPEG-2 Program Stream container used on DVD-Video discs, and its audio is most commonly AC3 (Dolby Digital) at bitrates between 192k and 448k, though some DVDs use DTS, MPEG audio, or LPCM instead. When FFmpeg demuxes a VOB file, it must parse the PS headers to locate and separate the audio elementary streams from the video and subtitle data. The wmav2 codec (Windows Media Audio version 2) is the default and most compatible WMA variant, offering better quality than the older wmav1 at equivalent bitrates. One important limitation is that WMA containers do not support chapter markers or multiple simultaneous audio tracks, so only one audio stream can be embedded in the output — a significant difference from the multi-stream capability of the source VOB. Metadata such as track title or artist information is not automatically transferred from VOB to WMA, as VOB files store metadata in IFO structures on the DVD rather than in the VOB streams themselves. File size will typically be smaller than the source VOB since the video stream is discarded and WMA at 128k is considerably compressed, though the reduction relative to just the audio portion depends on the original AC3 bitrate.