Extract Audio from WMV to AAC — Free Online Tool
Extract the audio track from a WMV file and save it as an AAC file, discarding the Windows Media Video stream entirely. This is ideal for pulling speech, music, or ambient audio out of WMV recordings encoded with WMA (wmav2) and repackaging it in the widely compatible AAC format used by Apple, Android, and streaming platforms.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
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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
WMV files use Microsoft's Advanced Systems Format (ASF) container, which typically pairs an msmpeg4 video stream with a wmav2 (Windows Media Audio) audio stream. During this conversion, FFmpeg completely drops the video stream using the -vn flag — no video decoding or encoding occurs at all. The wmav2 audio is then decoded from its proprietary Microsoft format and re-encoded into AAC using FFmpeg's built-in aac encoder at 128k bitrate. Because wmav2 and AAC use different psychoacoustic models and compression algorithms, a full decode-and-reencode is required — this is not a simple remux. The result is a standalone .aac file containing only the audio, compatible with iTunes, iOS, Android, and virtually all modern media players.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool. In the browser-based version of this tool, this runs via FFmpeg.wasm compiled to WebAssembly, executing entirely on your local machine without any server upload. |
-i input.wmv
|
Specifies the input WMV file using Microsoft's ASF container, which FFmpeg reads to identify the available video (msmpeg4) and audio (wmav2) streams before processing. |
-vn
|
Disables video output entirely — FFmpeg will not decode or include the msmpeg4 video stream from the WMV file in any form. This is the key flag that makes this an audio extraction rather than a full conversion, and it also speeds up processing significantly. |
-c:a aac
|
Specifies that the audio stream should be encoded using FFmpeg's built-in AAC encoder. Since the source audio is wmav2 (a proprietary Microsoft codec), a full decode-and-reencode into AAC is required — there is no way to copy the stream directly. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second, which is the standard default for AAC and provides a good balance of file size and audio quality for speech and typical music content extracted from WMV sources. |
output.aac
|
Defines the output filename and tells FFmpeg to write a raw AAC audio stream. The .aac extension produces a containerless AAC file compatible with iTunes, iOS, Android, and most modern media players and streaming workflows. |
Common Use Cases
- Pull the audio from a Windows Media Player screen recording or tutorial video to create a podcast episode or audio guide without the visual component
- Extract narration or voiceover from a WMV corporate presentation to repurpose as an AAC audio file for mobile listening or archiving
- Convert a WMV music video or concert recording saved from an older Windows system into an AAC audio file compatible with iTunes or an iPhone
- Strip the audio track from a WMV surveillance or CCTV clip for transcription or evidence logging without storing the large video file
- Migrate a library of old WMV radio recordings or audiobooks captured in Windows Media Player into AAC for playback on modern devices that no longer support WMA
- Extract the audio from a WMV lecture or webinar recording to upload as an AAC podcast episode to platforms like Spotify or Apple Podcasts
Frequently Asked Questions
Yes, there will be some generation loss because this conversion requires decoding the wmav2 audio and re-encoding it into AAC — two lossy codecs with different compression algorithms. The wmav2 audio in the original WMV was already lossy, so you are working from a compressed source. At the default 128k bitrate, AAC generally sounds comparable to or slightly better than wmav2 at the same bitrate due to AAC's more efficient psychoacoustic model, but you cannot fully recover quality lost in the original wmav2 encoding.
A raw .aac file contains the AAC audio stream with minimal container overhead, while .m4a is an AAC stream wrapped in an MPEG-4 (MP4) container. Both use the same underlying AAC audio encoding. The .aac format is slightly simpler and universally readable by AAC-compatible players, but if you need broader compatibility with iTunes or want to embed metadata tags like artist or album, you may prefer an .m4a container. You can produce .m4a by simply changing the output filename to output.m4a in the FFmpeg command.
Metadata handling from WMV to raw AAC is limited. WMV files store metadata in ASF container tags (such as Title, Author, and Description), and FFmpeg will attempt to map recognized fields to the output. However, a bare .aac file has very limited metadata support compared to a container format like .m4a or .mp3. If preserving metadata is important, consider outputting to .m4a instead, which supports full ID3-style tagging within the MPEG-4 container.
Change the value after -b:a in the command to adjust the audio bitrate. For example, replace 128k with 192k or 256k for higher quality output: ffmpeg -i input.wmv -vn -c:a aac -b:a 192k output.aac. Higher bitrates produce larger files with better fidelity, though gains above 192k are rarely perceptible for typical speech or compressed source material. Since the wmav2 source is already lossy, very high bitrates like 320k will not recover lost detail.
Yes. On Linux or macOS, you can loop over all WMV files in a directory with: for f in *.wmv; do ffmpeg -i "$f" -vn -c:a aac -b:a 128k "${f%.wmv}.aac"; done. On Windows Command Prompt, use: for %f in (*.wmv) do ffmpeg -i "%f" -vn -c:a aac -b:a 128k "%~nf.aac". Each WMV file will produce a corresponding .aac file with the same base name.
By default, FFmpeg selects only the best (usually first) audio stream for the output, so only one audio track will be extracted. WMV files using the ASF container do technically support multiple audio streams. If your WMV has multiple audio tracks and you want a specific one, add -map 0:a:1 (for the second audio track, zero-indexed) to the command before the output filename: ffmpeg -i input.wmv -vn -map 0:a:1 -c:a aac -b:a 128k output.aac.
Technical Notes
WMV files use Microsoft's proprietary ASF (Advanced Systems Format) container, which requires the special FFmpeg flag -f asf for format disambiguation in some edge cases. The audio codec in most WMV files is wmav2 (Windows Media Audio v2), a proprietary lossy codec that is not natively supported on Apple devices or most non-Windows platforms without third-party software — which is a primary motivation for this conversion. FFmpeg's built-in aac encoder produces compliant AAC-LC output, which is the most broadly compatible AAC profile across iOS, Android, web browsers, and streaming services. If you have access to the libfdk_aac encoder (requires a custom FFmpeg build), you can substitute -c:a libfdk_aac for marginally better quality at the same bitrate due to its superior psychoacoustic tuning. Note that WMV files with DRM (Digital Rights Management) protection cannot be processed by FFmpeg or this tool — only unprotected WMV files can be converted. The -vn flag ensures zero video processing overhead, making this extraction fast even for long WMV files since only the audio stream is decoded and re-encoded.