Convert MKV to WMA — Free Online Tool
Convert MKV files to WMA audio, extracting the audio track and encoding it with Microsoft's WMAv2 codec at 128k bitrate. Ideal for stripping audio from Matroska video containers into a Windows Media Audio file compatible with legacy Windows media players and Microsoft ecosystem software.
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FFmpeg Command
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Estimated output:
Conversion Complete!
DownloadHow It Works
During this conversion, FFmpeg discards all video, subtitle, and chapter data from the MKV container — none of it can be carried into WMA, which is a pure audio format. The audio track (commonly AAC, MP3, Opus, Vorbis, or FLAC inside an MKV) is decoded from its original codec and re-encoded into WMAv2, Microsoft's second-generation Windows Media Audio codec. This is a full transcode of the audio stream, not a copy — meaning the audio is decoded to raw PCM and then compressed again using WMAv2's lossy compression algorithm. If the source MKV contained lossless audio (e.g., FLAC), the output WMA will be lossy. If the source already contained lossy audio, this introduces a second generation of lossy compression, which can subtly degrade quality. Multiple audio tracks in the MKV are reduced to a single track in the output, as WMA does not support multi-track containers.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, the open-source multimedia processing engine that handles all decoding, filtering, and encoding operations in this conversion pipeline. |
-i input.mkv
|
Specifies the input file — in this case a Matroska (.mkv) container, which may contain video, audio, subtitles, chapters, and multiple tracks that FFmpeg will parse and make available for processing. |
-c:a wmav2
|
Selects WMAv2 (Windows Media Audio version 2) as the audio encoder for the output stream, producing a lossy-compressed audio file compatible with Microsoft's WMA format. The video stream from the MKV is implicitly dropped because WMA has no video stream support. |
-b:a 128k
|
Sets the audio bitrate to 128 kilobits per second for the WMAv2 encoder, controlling the tradeoff between file size and audio fidelity — 128k is the default and produces reasonably good quality for music and voice content in a WMA file. |
output.wma
|
Defines the output filename with the .wma extension, which tells FFmpeg to wrap the encoded WMAv2 audio stream in Microsoft's ASF (Advanced Systems Format) container, the standard container used by all WMA files. |
Common Use Cases
- Transferring audio content from an MKV movie or TV episode rip into Windows Media Player or Zune software on older Windows machines that natively handle WMA but not MKV
- Preparing audio files for playback on older Microsoft-ecosystem portable devices, such as first- or second-generation Zune players, which require WMA format
- Extracting a music concert or live performance recorded in MKV format into a standalone WMA file for archiving in a Windows Media Center library
- Converting an MKV audiobook or lecture recording into WMA for use with corporate Windows environments that use WMA-based DRM licensing workflows
- Stripping audio from an MKV screen recording or tutorial video to produce a WMA audio-only version for users who want to listen without watching
- Producing WMA-compatible audio files from MKV sources for upload to platforms or legacy content management systems that only accept Windows Media Audio formats
Frequently Asked Questions
Yes, always. WMA is a lossy-only format, so regardless of what audio codec was in the source MKV, the output will be lossy WMAv2. If your MKV contained lossless FLAC audio, converting to WMA introduces lossy compression for the first time. If your MKV already had lossy audio (such as AAC or MP3), the conversion involves decoding that lossy stream and re-encoding it with WMAv2, which is a second-generation encode and will degrade quality somewhat compared to the original. At 128k bitrate, WMAv2 produces acceptable results for casual listening but is not suitable for archival purposes.
They are all permanently discarded. WMA is a pure audio container and has no ability to store video streams, subtitle tracks, chapter markers, or multiple audio tracks. Only the first (or default) audio track from the MKV is encoded into the output WMA file. If your MKV contains multiple audio tracks in different languages or formats, only one will be extracted — by default FFmpeg selects the first audio stream.
WMAv1 (wmav1) is the original Windows Media Audio codec from the late 1990s with relatively poor compression efficiency. WMAv2 (wmav2) is its successor, offering significantly better audio quality at equivalent bitrates through improved psychoacoustic modeling and entropy coding. WMAv2 is also far more widely supported across Windows software and devices than WMAv1. This tool defaults to wmav2 because it is the current standard WMA codec and produces better results in virtually every practical scenario.
Replace the value after -b:a in the command. For example, to encode at 192k bitrate, use: ffmpeg -i input.mkv -c:a wmav2 -b:a 192k output.wma. WMAv2 supports bitrates ranging from 64k (smaller file, lower quality, suitable for voice) up to 320k (larger file, near-transparent quality for music). The default of 128k is a reasonable balance for general audio content, but for music you may want 192k or higher.
Basic metadata tags such as title, artist, album, and track number are generally preserved during this conversion, as both MKV and WMA support standard metadata fields and FFmpeg maps them automatically. However, MKV can carry more complex or custom metadata that has no equivalent in WMA's metadata structure, and those fields will be silently dropped. Cover art embedded in the MKV is also typically not carried over to WMA output.
FFmpeg itself processes one file per command invocation, but you can batch process using a shell loop. On Windows Command Prompt: for %f in (*.mkv) do ffmpeg -i "%f" -c:a wmav2 -b:a 128k "%~nf.wma". On Linux or macOS bash: for f in *.mkv; do ffmpeg -i "$f" -c:a wmav2 -b:a 128k "${f%.mkv}.wma"; done. This will process every MKV in the current directory and produce a matching WMA file for each.
Technical Notes
WMA (Windows Media Audio) is a proprietary Microsoft codec and container, meaning its inner workings are not publicly documented. FFmpeg's wmav2 encoder is a clean-room reverse-engineered implementation that produces files compatible with Windows Media Player, Windows Media Center, and most WMA-supporting hardware. The WMA container is built on Microsoft's Advanced Systems Format (ASF), which supports DRM metadata fields — however, this tool does not apply any DRM. Because MKV can carry audio in dozens of codecs (including Opus, Vorbis, AAC-LC, HE-AAC, MP3, AC-3, DTS, and FLAC), the actual quality of the transcode depends heavily on what audio is inside your specific MKV file: high-bitrate source audio will yield better WMA output than low-bitrate source audio. WMAv2 is a fixed-bitrate lossy codec in this usage and does not support variable bitrate (VBR) encoding in FFmpeg's standard implementation without additional flags. The output file will be mono or stereo depending on the source channel count, though WMAv2 does not natively support more than two channels in most configurations — surround audio from the MKV will be downmixed. There is no video quality consideration here since the output is audio-only.