MyMediaTools

Convert AVI to WMV — Free Online Tool

Convert AVI files to WMV using FFmpeg.wasm entirely in your browser — no upload required. This conversion re-encodes video with Microsoft's MPEG-4 v3 (msmpeg4) codec and audio with WMA v2 (wmav2), producing an ASF-container WMV file optimized for Windows Media Player and legacy Windows environments.

FFmpeg Command

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Estimated output:

Conversion Complete!

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How It Works

AVI uses a simple RIFF-based container that can hold a wide variety of video and audio codecs. WMV, by contrast, is built on Microsoft's Advanced Systems Format (ASF) container and requires Microsoft-specific codecs — so this conversion always involves full re-encoding of both streams. The video is decoded from whatever codec is inside your AVI (commonly H.264 or MJPEG) and re-encoded using the msmpeg4 codec (Microsoft MPEG-4 Version 3, sometimes called MS-MPEG4v3), which is the native codec Windows Media Player was designed around. The audio is similarly re-encoded from MP3 or AAC into WMA v2 (wmav2), Microsoft's proprietary Windows Media Audio codec. Because ASF has its own interleaving and indexing structure quite different from AVI's RIFF chunks, FFmpeg also forces the output container with the '-f asf' flag to ensure the file is properly structured as WMV rather than being incorrectly wrapped.

What Each Flag Does

Flag What it does
ffmpeg Invokes the FFmpeg tool — in the browser this runs as FFmpeg.wasm compiled to WebAssembly, executing the identical command logic as the desktop version without sending your file to any server.
-i input.avi Specifies the input AVI file. FFmpeg reads its RIFF container structure to identify the video and audio streams inside — which may use codecs like H.264, MJPEG, MP3, or AAC — before decoding them for re-encoding into WMV.
-c:v msmpeg4 Sets the video codec to Microsoft MPEG-4 Version 3 (msmpeg4), the proprietary video codec native to the WMV/ASF ecosystem and required for authentic Windows Media Player compatibility. This fully re-encodes the video — it is not a stream copy.
-c:a wmav2 Sets the audio codec to Windows Media Audio Version 2 (wmav2), Microsoft's proprietary audio format that pairs with the WMV container. The AVI's audio — whether MP3 or AAC — is fully decoded and re-encoded into WMA v2.
-b:v 2000k Sets the target video bitrate to 2000 kilobits per second for the msmpeg4 encoder. WMV uses bitrate-based quality control rather than CRF, so this value directly determines the trade-off between file size and visual quality — raise it for sharper output on high-resolution AVI sources.
-b:a 128k Sets the WMA v2 audio bitrate to 128 kilobits per second, a standard quality level suitable for most speech and general audio content in converted AVI files. Increase to 192k or 256k for music-heavy content.
-f asf Explicitly forces the output container to ASF (Advanced Systems Format), which is the underlying container format shared by WMV files. This flag is required because FFmpeg needs explicit instruction to use the ASF muxer with the Microsoft MPEG-4 codec, ensuring the output is correctly structured for Windows Media Player playback.
output.wmv The output filename with the .wmv extension, which signals a Windows Media Video file to the operating system. The actual container is ASF (as forced by '-f asf'), and the .wmv extension ensures Windows associates the file with Windows Media Player by default.

Common Use Cases

  • Sending video files to colleagues or clients who use older Windows systems where Windows Media Player is the default and only installed player
  • Preparing video content for legacy Microsoft SharePoint or older corporate intranet portals that specifically require WMV uploads
  • Converting home video archives originally captured in AVI format for playback on older Windows XP or Vista machines that struggle with modern codecs
  • Meeting submission requirements for certain government or institutional video portals that mandate WMV format for compatibility with their Windows-based infrastructure
  • Reducing the codec footprint of an AVI file for distribution on Windows-centric platforms where installing codec packs is restricted by IT policy
  • Creating WMV-format video tutorials or demos for embedding in legacy Microsoft PowerPoint presentations using the Insert Movie feature

Frequently Asked Questions

Yes — this is a lossy-to-lossy re-encoding, meaning both video and audio are fully decoded and re-compressed. The msmpeg4 codec used in WMV is generally less efficient than modern codecs like H.264 that may already be inside your AVI, so at the same bitrate you may notice a slight reduction in visual quality. The default 2000k video bitrate is a reasonable starting point for standard-definition content, but for high-motion or high-resolution AVI files you may want to increase it. There is no lossless path from AVI to WMV — the ASF container only supports lossy Microsoft codecs.
WMV is actually a video profile of Microsoft's Advanced Systems Format (ASF) container — they share the same underlying format, just with different file extensions and intended use cases. FFmpeg doesn't automatically infer ASF from the .wmv extension when using Microsoft MPEG-4 codecs, so the '-f asf' flag explicitly forces the correct container muxer. Without it, FFmpeg might produce a malformed or incorrectly structured output file that Windows Media Player cannot open reliably.
AVI supports multiple audio tracks, and while WMV/ASF also technically supports them, FFmpeg's default behavior will map only the first audio track unless you specify additional mapping flags. If your AVI contains a secondary audio track — for example, a director's commentary or a dubbed language — it will be silently dropped during this conversion. If preserving multiple audio tracks is important, you would need to modify the FFmpeg command with explicit '-map' flags for each stream.
Yes — WMV uses bitrate-based quality control (unlike AVI's H.264 which uses CRF), so you adjust quality by changing the '-b:v' value. Replace '2000k' with a higher value like '4000k' or '6000k' for noticeably sharper output, especially for 1080p or high-motion content. Be aware that unlike CRF encoding, bitrate control in msmpeg4 can be inconsistent — some scenes may look great while others show blocking artifacts if the bitrate isn't high enough. For the audio, changing '-b:a 128k' to '192k' or '256k' will improve WMA audio fidelity.
AVI stores metadata in INFO chunks within its RIFF structure, while WMV/ASF uses a completely different metadata system based on ASF Header Objects with fields like Title, Author, Copyright, and Description. FFmpeg will attempt to map common metadata fields between the two formats during conversion, but the mapping is not always complete or perfectly accurate. Embedded AVI metadata like custom tags or non-standard fields may be lost. If metadata preservation is critical, verify the output file's tags after conversion using a tool like MediaInfo or ffprobe.
On Windows, you can run a batch conversion from the command prompt using: 'for %f in (*.avi) do ffmpeg -i "%f" -c:v msmpeg4 -c:a wmav2 -b:v 2000k -b:a 128k -f asf "%~nf.wmv"'. On Linux or macOS, use: 'for f in *.avi; do ffmpeg -i "$f" -c:v msmpeg4 -c:a wmav2 -b:v 2000k -b:a 128k -f asf "${f%.avi}.wmv"; done'. This is particularly useful for converting large AVI archives, and works best when run locally since the browser-based tool processes one file at a time.

Technical Notes

The msmpeg4 codec used here is Microsoft MPEG-4 Version 3 — a proprietary variant of the MPEG-4 Part 2 standard that is not interchangeable with standard MPEG-4 or H.264. It was designed specifically for Windows Media Player and has been frozen since the Windows XP era, which means it offers significantly lower compression efficiency compared to modern AVI codecs like libx264. Files produced with msmpeg4 at equivalent bitrates will typically appear softer or blockier than their H.264 AVI originals. The wmav2 audio codec is a mature, well-supported WMA implementation that performs reasonably at 128k, though it trails behind AAC at low bitrates. One important limitation: AVI files that use VBR (variable bitrate) audio or non-standard interleaving may occasionally cause sync issues during re-encoding — if you notice audio drift in the output, adding '-async 1' to the command can help. Subtitles and chapter markers from AVI are not preserved, as WMV's ASF container handles these differently and FFmpeg does not automatically transcode them in this conversion path. The resulting WMV file will carry an ASF index at the end of the file, enabling seeking in Windows Media Player without requiring the entire file to be buffered.

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