Extract Audio from WMV to ALAC — Free Online Tool
Extract lossless audio from WMV video files by converting the WMA (wmav2) audio stream to ALAC, Apple's lossless codec stored in an M4A container. Ideal for archiving audio from Windows Media Video files in a format fully compatible with iTunes, Apple Music, and the broader Apple ecosystem — without any quality loss.
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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
WMV files typically carry audio encoded with the WMA v2 (wmav2) codec, a lossy Microsoft proprietary format. During this conversion, FFmpeg discards the video stream entirely and re-encodes the WMA audio into ALAC (Apple Lossless Audio Codec), which uses lossless compression within an MPEG-4 (.m4a) container. Because the source audio is already lossy (wmav2), re-encoding to ALAC does not recover any quality that was lost during the original WMV encoding — but ALAC does perfectly preserve every bit of the audio data that exists in the source file, ensuring no further degradation. The result is an M4A file that is larger than the original WMA stream but represents the best possible preservation of the audio quality present in the WMV source.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, the open-source multimedia processing engine that powers this conversion both in the browser (via FFmpeg.wasm) and on the desktop command line. |
-i input.wmv
|
Specifies the input file — a WMV (Windows Media Video) file using the ASF container, which typically carries wmav2-encoded audio and MPEG-4-based video streams. |
-vn
|
Disables video output entirely, telling FFmpeg to ignore the WMV's video stream and produce an audio-only output file — essential for extracting a clean ALAC audio track. |
-c:a alac
|
Sets the audio codec to ALAC (Apple Lossless Audio Codec), which re-encodes the wmav2 audio from the WMV source into lossless compression suitable for M4A containers and Apple ecosystem playback. (Note: this flag appears twice in the resolved command, which is redundant but harmless — the last instance takes effect.) |
output.m4a
|
Defines the output filename with the .m4a extension, which tells FFmpeg to wrap the ALAC audio stream in an MPEG-4 container — the standard packaging for ALAC files compatible with iTunes, Apple Music, and iOS devices. |
Common Use Cases
- Archiving audio from corporate training videos or presentations originally distributed in WMV format for long-term lossless storage on Apple devices
- Importing audio from Windows Media Video recordings into an iTunes or Apple Music library, where ALAC is the preferred lossless format
- Extracting a music performance or concert recording from a WMV file to preserve the full audio fidelity available before any further editing or mastering
- Stripping audio from WMV screencasts or tutorial videos to create standalone audio tracks for podcast production on macOS
- Migrating a legacy archive of WMV media files to an Apple-centric workflow by extracting audio in a losslessly compressed, iTunes-compatible format
- Preparing WMV-sourced audio for use in Logic Pro or GarageBand, where ALAC M4A files integrate natively without transcoding overhead
Frequently Asked Questions
No — converting from WMV to ALAC will not improve audio quality. The original WMV file uses the wmav2 codec, which is a lossy format, meaning some audio data was permanently discarded when the WMV was first created. ALAC is a lossless codec, so it will perfectly preserve the audio data that survives in the WMV source, but it cannot reconstruct the information that was already lost. Think of it as making a perfect copy of an imperfect original — no further degradation, but no recovery either.
WMV files use wmav2, a lossy codec that achieves small file sizes by permanently discarding audio data the encoder deems inaudible. ALAC, by contrast, uses lossless compression — it retains all audio data and can only compress what is mathematically redundant. Because ALAC cannot throw away audio information to save space, its output files will always be larger than a lossy WMA stream representing the same duration of audio. This is the inherent tradeoff of lossless archiving.
ALAC was originally Apple-proprietary but was open-sourced by Apple in 2011, and support has since spread broadly. On Windows, applications like VLC, foobar2000, and MPC-HC can play ALAC M4A files natively. However, Windows Media Player does not support ALAC without additional codecs, which is an ironic limitation given that the source format here is Microsoft's own WMV. If your target audience uses Windows-only media players, consider whether FLAC might be a more universally compatible lossless alternative.
FFmpeg will attempt to copy supported metadata tags (such as title, artist, and album) from the WMV/ASF container into the MPEG-4 container used by ALAC. However, WMV uses the ASF (Advanced Systems Format) metadata schema, which does not map perfectly to the iTunes-style tags used in M4A files. Common fields like title and artist typically transfer correctly, but more obscure or Windows Media–specific tags may be dropped or need manual cleanup after conversion.
The command shown targets a single file, but you can adapt it for batch processing using a shell loop. On Linux or macOS, run: for f in *.wmv; do ffmpeg -i "$f" -vn -c:a alac "${f%.wmv}.m4a"; done. On Windows Command Prompt, use: for %f in (*.wmv) do ffmpeg -i "%f" -vn -c:a alac "%~nf.m4a". This processes every WMV in the current directory and outputs a corresponding ALAC M4A file. The browser-based tool handles one file at a time, so the FFmpeg command is particularly valuable for large batch jobs.
ALAC is a lossless codec, so the concept of a target bitrate does not apply — the encoder does not discard audio data to hit a size target. The output bitrate of an ALAC file is determined entirely by the complexity and sample rate of the source audio, not by a user-specified parameter. This is why the command uses only -c:a alac without any -b:a flag, unlike lossy formats such as MP3 or AAC where you would specify a bitrate like 320k or 128k.
Technical Notes
The source WMV format uses the ASF (Advanced Systems Format) container — indicated by the -f asf flag in FFmpeg — with wmav2 as the default audio codec. The wmav2 codec typically operates at bitrates between 64k and 192k in real-world WMV files, meaning the decoded audio PCM data fed into the ALAC encoder will already reflect those lossy compression decisions. ALAC stores audio in an MPEG-4 container (.m4a) and supports standard PCM sample rates including 44.1 kHz, 48 kHz, 88.2 kHz, and 96 kHz, so whatever sample rate the WMV source uses will be preserved in the output. One known limitation is that WMV's ASF container supports multiple audio tracks, but ALAC M4A does not — if the source WMV contains multiple audio streams, only the default stream will be extracted. ALAC M4A supports chapter markers, though WMV does not, so no chapter data will be present in the output unless added manually post-conversion. The M4A container supports rich iTunes-compatible metadata tagging, making the output files well-suited for library management in Apple Music or third-party taggers like MusicBrainz Picard.