Convert AAC to WMA — Free Online Tool
Convert AAC audio files to WMA format using the wmav2 codec, entirely in your browser with no file uploads required. This is ideal for moving iTunes-compatible AAC audio into Microsoft's Windows Media Audio ecosystem for use with legacy Windows software, Windows Media Player, or DRM-enabled media workflows.
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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
Both AAC and WMA are lossy compressed audio formats, which means this conversion is a lossy-to-lossy transcode — not a simple container remux. The AAC audio stream must be fully decoded back to raw PCM audio and then re-encoded using the wmav2 codec (Windows Media Audio version 2). Every re-encoding step introduces generation loss, as compression artifacts from the original AAC encoding are baked in before the new WMA compression artifacts are added. The output bitrate defaults to 128k, matching the input's typical default, which helps minimize but cannot eliminate quality degradation. No video, subtitle, chapter, or transparency data is involved since both formats are audio-only.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which handles the full decode-encode pipeline: reading and demuxing the AAC input, decoding the AAC audio to raw PCM, and re-encoding it as WMA audio. |
-i input.aac
|
Specifies the input AAC audio file. FFmpeg reads the AAC bitstream, identifies it as an AAC-encoded audio track, and prepares it for decoding prior to WMA re-encoding. |
-c:a wmav2
|
Sets the audio codec to wmav2 (Windows Media Audio version 2), Microsoft's standard WMA encoder. This tells FFmpeg to re-encode the decoded PCM audio into the WMA format that is broadly compatible with Windows Media Player, Windows devices, and WMA-supporting portable players. |
-b:a 128k
|
Sets the WMA audio bitrate to 128 kilobits per second, matching the typical default AAC bitrate to balance file size and audio quality during this lossy-to-lossy transcode. You can raise this (e.g., 192k or 256k) to reduce the relative quality impact of re-encoding. |
output.wma
|
Defines the output filename and tells FFmpeg to write an ASF/WMA container file. The .wma extension signals FFmpeg to wrap the wmav2-encoded audio stream in Microsoft's Advanced Systems Format container. |
Common Use Cases
- Preparing audio files for playback on older Windows devices or media centers that support WMA but not AAC natively
- Converting iTunes-purchased or Apple-encoded AAC files into WMA format for compatibility with Windows Media Player libraries
- Supplying WMA audio to enterprise or broadcasting workflows that mandate Microsoft-format deliverables
- Migrating an AAC-based music collection to WMA for use with a portable media player or car stereo that only reads WMA files
- Creating WMA versions of AAC podcast episodes or audiobooks for distribution through platforms or stores that accept WMA as a preferred format
- Testing wmav2 encoder output quality against AAC source material before committing to a large batch conversion pipeline
Frequently Asked Questions
Yes — this is a lossy-to-lossy transcode, so quality loss is unavoidable. Your AAC file was already compressed, and the audio must be fully decoded and re-encoded into WMA, stacking a second round of compression artifacts on top of the first. To minimize the damage, use the highest bitrate your use case permits (e.g., 192k or 256k) rather than the default 128k, and avoid converting the same file multiple times.
wmav2 (Windows Media Audio version 2) is the standard, widely supported generation of the WMA codec and offers better compression efficiency and audio quality than the older wmav1. Nearly all WMA-compatible players and devices support wmav2, making it the correct default for general-purpose AAC-to-WMA conversion. wmav1 exists mainly for compatibility with very old or specialized Windows Media software.
FFmpeg will attempt to map standard metadata tags (title, artist, album, track number, etc.) from the AAC file to the WMA container's metadata fields during conversion. However, AAC and WMA use different tagging systems — AAC typically uses iTunes-style MP4 atoms, while WMA uses ASF attribute pairs — and some non-standard or extended tags may not transfer cleanly. It is worth inspecting the output file's metadata afterward to confirm accuracy.
Replace the value after -b:a in the command with your desired bitrate. For example, to encode at 192 kbps use: ffmpeg -i input.aac -c:a wmav2 -b:a 192k output.wma. WMA supports common bitrates including 64k, 96k, 128k, 160k, 192k, 256k, and 320k. Keep in mind that since the source is a lossy AAC file, increasing the WMA bitrate beyond the original AAC bitrate will increase file size without recovering lost detail.
WMA natively supports Microsoft's DRM (Digital Rights Management) system, which is one reason it became common in early digital music stores. However, the FFmpeg conversion tool produces standard, unprotected WMA files — it does not apply DRM. If you need DRM-protected WMA output, that requires additional Microsoft licensing tools outside the scope of FFmpeg.
Yes. On Linux or macOS you can use a shell loop: for f in *.aac; do ffmpeg -i "$f" -c:a wmav2 -b:a 128k "${f%.aac}.wma"; done. On Windows Command Prompt: for %f in (*.aac) do ffmpeg -i "%f" -c:a wmav2 -b:a 128k "%~nf.wma". This applies the same wmav2 encoding settings to every AAC file in the current directory and is especially useful for large music library migrations.
Technical Notes
The WMA container is based on Microsoft's Advanced Systems Format (ASF), which adds overhead not present in the raw AAC (ADTS or M4A) container, so WMA files at equivalent bitrates will be slightly larger due to ASF framing. wmav2 is a transform-based lossy codec similar in approach to AAC but uses Microsoft's proprietary psychoacoustic model, which generally performs comparably to MP3 but is considered slightly inferior to AAC at the same bitrate — meaning your WMA output may perceptibly sound worse than the AAC source even at matching bitrates, independent of the re-encoding penalty. AAC's features such as HE-AAC spectral band replication (SBR) have no equivalent mapping in wmav2, so any efficiency gains from HE-AAC encoding in the source file will not be replicated. Neither AAC nor WMA supports embedded subtitles, chapters, video, or cover art in this pure audio context, though WMA via ASF technically allows cover art attachment through extended content description attributes — FFmpeg may or may not preserve embedded album art depending on the source file structure.