Convert RMVB to WMV — Free Online Tool
Convert RMVB files to WMV by re-encoding RealNetworks' variable bitrate video into Microsoft's Advanced Systems Format container using the msmpeg4 video codec and wmav2 audio codec. This is ideal for making legacy RealMedia content playable in Windows Media Player and other Windows-native applications.
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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
RMVB files use RealNetworks' proprietary RealVideo and RealAudio codecs inside a RealMedia container, which virtually no modern software supports natively. During this conversion, FFmpeg fully decodes the RealVideo stream and re-encodes it using the msmpeg4 codec (Microsoft MPEG-4 Version 3), while the audio is decoded and re-encoded using wmav2 (Windows Media Audio v2). The output is wrapped in an ASF (Advanced Systems Format) container — the underlying format behind WMV files — specified explicitly via the '-f asf' flag. Because both the video and audio streams must be fully transcoded (not remuxed), this is a computationally intensive process, and some quality loss compared to the original is inevitable since both the source and destination formats are lossy.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg tool, which handles the full decode-and-re-encode pipeline needed to convert the proprietary RealMedia RMVB format into a WMV/ASF file using Microsoft codecs. |
-i input.rmvb
|
Specifies the input RMVB file. FFmpeg uses its built-in reverse-engineered RealMedia demuxer and RealVideo/RealAudio decoders to read the variable bitrate stream from this proprietary container. |
-c:v msmpeg4
|
Sets the video encoder to Microsoft MPEG-4 Version 3 (msmpeg4), which is the standard video codec for WMV files and is natively supported by Windows Media Player and the ASF container format. |
-c:a wmav2
|
Sets the audio encoder to Windows Media Audio v2 (wmav2), the standard lossy audio codec for WMV/ASF files, replacing the RealAudio stream from the original RMVB with a widely compatible Windows Media audio track. |
-b:v 2000k
|
Targets a video bitrate of 2000 kilobits per second for the msmpeg4 encoder. Unlike the RMVB source which uses variable quality-based encoding, WMV uses fixed target bitrates to control file size and quality. |
-b:a 128k
|
Sets the audio bitrate to 128 kilobits per second for the wmav2 encoder, providing a standard quality level that balances file size and audio fidelity for typical speech and music content. |
-f asf
|
Explicitly forces the output container to ASF (Advanced Systems Format), the underlying container format that WMV files use. This flag ensures correct container structure even though the output filename ends in .wmv. |
output.wmv
|
Specifies the output filename. The .wmv extension signals that this is a Windows Media Video file — an ASF container holding msmpeg4 video and wmav2 audio — ready for playback in Windows Media Player and compatible applications. |
Common Use Cases
- Playing old downloaded movies or TV episodes stored in RMVB format on a Windows PC using Windows Media Player, which does not support RealMedia natively
- Archiving a collection of RMVB files downloaded in the early 2000s into a more durable and widely readable format before RealPlayer support disappears entirely
- Submitting video content to a legacy enterprise system or intranet media server that only accepts WMV/ASF files as input
- Preparing RMVB-encoded video content for editing in older versions of Windows Movie Maker or other Windows-native video editors that require WMV input
- Converting RMVB video files for playback on older Windows-based set-top boxes, kiosks, or embedded devices that only support Windows Media codecs
- Standardizing a mixed media library of RMVB and other legacy formats into a single WMV format for compatibility with a Windows-based media management system
Frequently Asked Questions
Yes, some quality loss is unavoidable because both RMVB and WMV are lossy formats, meaning this conversion involves decoding a lossy source and re-encoding it with a different lossy codec. The RealVideo stream is fully decoded and then compressed again using msmpeg4, and the RealAudio stream is re-encoded as wmav2. To minimize quality loss, you can increase the video bitrate above the default 2000k using the '-b:v' flag — for example, '-b:v 4000k' or '-b:v 6000k' — though the final quality is ultimately bounded by whatever quality existed in the original RMVB file.
WMV files are actually ASF (Advanced Systems Format) containers — WMV is essentially a branded subset of ASF used specifically for Windows Media Video content. FFmpeg uses the explicit '-f asf' flag to ensure the correct container format is written, since FFmpeg's internal format detection from the '.wmv' extension alone can sometimes be ambiguous. The resulting file is a fully standard WMV file that Windows Media Player and compatible applications will recognize and play correctly.
Yes, you can substitute 'msmpeg4v2' for 'msmpeg4' in the command by changing '-c:v msmpeg4' to '-c:v msmpeg4v2'. The msmpeg4v2 codec produces Microsoft MPEG-4 Version 2 output, which is slightly older than Version 3 (msmpeg4) and may offer broader compatibility with very old Windows Media Player versions, though Version 3 is generally preferred for better compression efficiency. Note that modern WMV codecs like wmv2 or wmv3 are not well supported in FFmpeg's encoding path, so msmpeg4 remains the most practical choice.
To adjust video quality, change the '-b:v 2000k' value to a higher or lower bitrate — for example, '-b:v 4000k' for better quality or '-b:v 1000k' for a smaller file size. For audio quality, modify '-b:a 128k' to values like '192k' or '256k' for higher fidelity, or '96k' or '64k' for smaller files. Unlike the RMVB source format which uses CRF-based quality control, WMV relies on fixed target bitrates, so higher numbers directly correspond to larger file sizes and better quality.
Neither RMVB nor WMV supports subtitles or chapters in a meaningful cross-compatible way, so no subtitle or chapter data will be carried over. Basic metadata such as title or author tags may not transfer reliably either, as RealMedia's metadata schema differs significantly from ASF's metadata structure and FFmpeg does not always map these fields automatically. If preserving metadata is important, you may need to add it manually after conversion using a tag editor that supports WMV/ASF files.
Yes, you can adapt the command for batch processing on your desktop. On Linux or macOS, you can use a shell loop such as: 'for f in *.rmvb; do ffmpeg -i "$f" -c:v msmpeg4 -c:a wmav2 -b:v 2000k -b:a 128k -f asf "${f%.rmvb}.wmv"; done'. On Windows Command Prompt, use: 'for %f in (*.rmvb) do ffmpeg -i "%f" -c:v msmpeg4 -c:a wmav2 -b:v 2000k -b:a 128k -f asf "%~nf.wmv"'. The browser-based tool processes one file at a time, so the FFmpeg command is especially useful for large batches or files over 1GB.
Technical Notes
The RMVB format uses RealNetworks' proprietary RealVideo 8/9/10 and RealAudio codecs, which are only decodable by FFmpeg through its built-in reverse-engineered support — encoding back to RealVideo is not supported by FFmpeg at all, making RMVB effectively a read-only format in this toolchain. The WMV output uses msmpeg4 (Microsoft MPEG-4 Version 3), which despite its name is not MPEG-4 Part 2 compliant but rather a Microsoft proprietary variant derived from it. The ASF container supports multiple audio tracks, but since RMVB does not, only a single audio stream will be present in the output. Neither format supports transparency or lossless encoding, so this conversion is purely lossy-to-lossy. File sizes after conversion can vary significantly depending on the source RMVB bitrate — RMVB's variable bitrate encoding sometimes stores content at very low average bitrates, so converting to a fixed 2000k WMV target may actually produce a larger output file than the original. The wmav2 audio codec is well-suited to the ASF container and produces good quality at 128k, which is the default used here.