Convert MP4 to WMV — Free Online Tool
Convert MP4 files to WMV format using the Microsoft MPEG-4 v3 (msmpeg4) video codec and WMA v2 audio, encoded entirely in your browser with no file uploads. Ideal for making modern MP4 content compatible with Windows Media Player and legacy Windows-based workflows.
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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
Unlike MP4-to-MP4 remuxing or container-swap conversions, this process requires full re-encoding of both the video and audio streams. The H.264 or H.265 video inside your MP4 is decoded and re-encoded using the msmpeg4 codec, a Microsoft-proprietary MPEG-4 variant that predates the modern ISO standard and is natively recognized by Windows Media Player. The AAC or MP3 audio is similarly re-encoded into WMA v2 (wmav2), Microsoft's standard lossy audio codec for the ASF container. The output is wrapped in an ASF (Advanced Systems Format) container with a .wmv extension — the same underlying container used by both WMV and WMA files. Note that MP4 features like embedded subtitles, chapter markers, and multiple audio tracks are not carried over, as the WMV/ASF format does not support these in the same way.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary, the open-source multimedia processing engine that handles all decoding, re-encoding, and container muxing for this conversion. |
-i input.mp4
|
Specifies the source MP4 file as the input. FFmpeg will demux the ASF container and decode the contained video (typically H.264 or H.265) and audio (typically AAC) streams for re-encoding. |
-c:v msmpeg4
|
Sets the video encoder to Microsoft MPEG-4 Version 3 (msmpeg4), the legacy codec required for native Windows Media Player compatibility. This triggers a full re-encode of the video stream from its original codec into this older Microsoft-proprietary format. |
-c:a wmav2
|
Sets the audio encoder to Windows Media Audio Version 2 (wmav2), Microsoft's standard lossy audio codec for ASF/WMV containers. This re-encodes the source AAC or MP3 audio into WMA format, which Windows Media Player expects and handles natively. |
-b:v 2000k
|
Sets the video bitrate to 2000 kilobits per second for the msmpeg4-encoded output. This is the target average bitrate for the video stream; 2000k is a reasonable default for standard and moderate HD content, though the msmpeg4 codec is less efficient than H.264 at equivalent bitrates. |
-b:a 128k
|
Sets the WMA v2 audio bitrate to 128 kilobits per second, which provides standard stereo audio quality suitable for most speech and music content in a WMV file. |
-f asf
|
Forces the output container format to ASF (Advanced Systems Format), which is the underlying container for all WMV files. This flag is necessary because WMV is not a true standalone container — the .wmv extension is a convention for video-bearing ASF files. |
output.wmv
|
Specifies the output filename with the .wmv extension, producing a Windows Media Video file that can be played by Windows Media Player and other WMV-compatible applications on Windows systems. |
Common Use Cases
- Submitting video content to corporate intranet systems or internal media servers that only accept WMV files and were built around Windows Media Services
- Preparing video files for playback on older Windows XP or Windows Vista machines where Windows Media Player is the only available media player
- Delivering video to clients or institutions using legacy Windows-based digital signage software that requires the ASF/WMV container
- Converting MP4 recordings for use in older versions of Microsoft PowerPoint (2003–2007) that natively embed WMV rather than MP4
- Fulfilling broadcast or archival submission requirements from organizations that standardized on Windows Media Video before H.264 became dominant
- Generating a WMV copy of an MP4 tutorial or training video for distribution via a Windows-based LMS that only accepts WMV uploads
Frequently Asked Questions
Yes, this conversion involves lossy re-encoding and will introduce some quality degradation. Your MP4's video stream (typically H.264 or H.265) must be fully decoded and re-encoded into the msmpeg4 codec, which is an older and less efficient codec than modern H.264. The default bitrate of 2000k is reasonable for standard definition and moderate HD content, but you may notice softer detail or compression artifacts compared to the original, especially on complex motion or fine textures. For best results, use the highest source quality MP4 you have.
WMV is not actually a standalone container format — it is a codec family (Windows Media Video) packaged inside Microsoft's ASF (Advanced Systems Format) container. The .wmv file extension is simply a convention for ASF files that primarily contain video. The FFmpeg flag '-f asf' explicitly instructs FFmpeg to write the ASF container format, which is what produces a valid .wmv file. Without this flag, FFmpeg might not correctly identify the output format from the .wmv extension alone.
No. The WMV/ASF format does not support embedded subtitle tracks or chapter markers in the same way MP4 does. Any subtitle streams (SRT, ASS, MOV_TEXT) and chapter metadata present in your source MP4 will be dropped during conversion. If subtitles are essential, you would need to burn them directly into the video frames before or during conversion, which requires a different FFmpeg workflow using the 'subtitles' or 'ass' video filter.
Replace the '-b:v 2000k' value with a higher bitrate. For 720p content, try '-b:v 4000k'; for 1080p, '-b:v 6000k' or '-b:v 8000k' is more appropriate. The full modified command would look like: ffmpeg -i input.mp4 -c:v msmpeg4 -c:a wmav2 -b:v 4000k -b:a 128k -f asf output.wmv. Keep in mind that the msmpeg4 codec has efficiency limitations, so very high bitrates may produce diminishing returns compared to what H.264 achieves at the same bitrate.
Yes. On Windows, you can use a FOR loop in the Command Prompt: 'for %f in (*.mp4) do ffmpeg -i "%f" -c:v msmpeg4 -c:a wmav2 -b:v 2000k -b:a 128k -f asf "%~nf.wmv"'. On macOS or Linux, use: 'for f in *.mp4; do ffmpeg -i "$f" -c:v msmpeg4 -c:a wmav2 -b:v 2000k -b:a 128k -f asf "${f%.mp4}.wmv"; done'. This is especially useful for processing large batches of files or files over 1GB, which exceed the browser tool's size limit.
No — despite the similar name, they are quite different. The msmpeg4 codec (specifically version 3, also called MS MPEG-4 v3 or DivX) is a Microsoft-proprietary codec developed in the late 1990s and is technically a non-standard variant of MPEG-4 Part 2. Modern MP4 files typically use H.264 (MPEG-4 Part 10/AVC) or H.265 (HEVC), which are far more efficient and standardized codecs developed under the ISO/IEC umbrella. The msmpeg4 codec exists in FFmpeg specifically for compatibility with legacy Microsoft applications and Windows Media Player.
Technical Notes
The msmpeg4 codec written by FFmpeg corresponds to Microsoft MPEG-4 Version 3, the codec that historically underpinned early WMV files and was the basis for the original DivX codec. It is significantly less compression-efficient than H.264 or H.265, meaning you need higher bitrates to achieve comparable visual quality. The wmav2 audio codec is WMA Version 2, a well-supported Microsoft audio codec that produces acceptable quality at 128k for stereo content. One important limitation of this conversion is metadata handling: while MP4 containers support rich metadata (title, artist, encoder, creation date, multiple audio tracks), the ASF container has a different metadata schema and FFmpeg's MP4-to-ASF mapping may drop or fail to translate certain tags. Multiple audio tracks technically have some support in ASF, but most WMV players treat only the first audio track. DRM (Digital Rights Management) support is a native ASF/WMV feature, but applying DRM requires Microsoft's proprietary toolchain and cannot be added via FFmpeg. Finally, because this is a fully lossy re-encode of both streams, there is no way to perform a lossless or stream-copy conversion from MP4 to WMV — the codec families are fundamentally incompatible for direct stream copying.