Trim WMV — Free Online Tool
Trim a WMV file to a specific start and end time, outputting a shorter WMV clip that preserves the original ASF container, msmpeg4 video codec, and wmav2 audio — no re-encoding required. Ideal for cutting out segments from Windows Media Video files while keeping the original quality and bitrate intact.
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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
This tool performs a stream-copy trim on your WMV file using FFmpeg's `-c copy` flag, meaning neither the msmpeg4 video stream nor the wmav2 audio stream is re-encoded. The original compressed data is extracted between the specified timestamps and repackaged into a new ASF container (the underlying format of WMV). Because WMV uses a fixed-bitrate encoding model and the ASF container does not always align keyframes densely, the actual cut point may snap to the nearest keyframe rather than the exact frame you specified — this is a known characteristic of stream-copy trimming in WMV files. The output file will be structurally identical to the source, with the same codec, bitrate, and quality, just shorter in duration.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg binary. This is the command-line tool that runs inside your browser via WebAssembly (FFmpeg.wasm) — the same binary you would install locally on Windows, macOS, or Linux to run this command on files larger than 1GB. |
-i input.wmv
|
Specifies the input WMV file. FFmpeg reads the ASF container, detects the msmpeg4 video and wmav2 audio streams, and prepares them for the trim operation. |
-ss 00:00:00
|
Sets the trim start time to the beginning of the file (0 seconds). Change this timestamp to any point in the video — for example, `00:01:15` to start at 1 minute 15 seconds. When placed after `-i`, FFmpeg decodes to this point accurately, which matters for keyframe-sparse WMV streams. |
-to 00:00:10
|
Sets the trim end time to 10 seconds into the file. This tells FFmpeg to stop writing output at this position. Replace with any timestamp representing where you want the clip to end, using `HH:MM:SS` format. |
-c copy
|
Copies all streams — both the msmpeg4 video and wmav2 audio — without re-encoding. This makes the trim nearly instantaneous, preserves the original quality and bitrate exactly, and avoids any generation loss that would occur if the WMV streams were decoded and re-encoded. |
output.wmv
|
Specifies the output filename with a .wmv extension. Combined with the `-f asf` flag embedded in the tool's format handling, FFmpeg writes a valid ASF/WMV container that is compatible with Windows Media Player and other WMV-aware players. |
Common Use Cases
- Remove dead air or countdown timers from the beginning of a recorded Windows Media Player broadcast before sharing it
- Extract a specific presentation segment from a long WMV screen recording captured with older Windows tools like Windows Media Encoder
- Clip a highlight reel from a WMV sports or event recording originally distributed for Windows Media Player playback
- Trim a WMV training video to isolate a single module or chapter before uploading to a legacy corporate LMS that requires WMV format
- Cut out the intro and outro from a WMV file produced by a DRM-free Windows-based video editor to reduce file size before streaming
- Shorten a WMV video to meet a duration requirement for a platform that still accepts Windows Media Video as an upload format
Frequently Asked Questions
No — because the command uses `-c copy`, the msmpeg4 video and wmav2 audio streams are copied byte-for-byte without any re-encoding. There is no generation loss, and the bitrate remains exactly what it was in the original file. The only trade-off is that the cut points are snapped to the nearest keyframe in the WMV stream, so the trim may be off by a fraction of a second at the start or end.
WMV files encoded with msmpeg4 typically have keyframes spaced several seconds apart. When using `-c copy` (stream copy without re-encoding), FFmpeg must begin the output at a keyframe boundary, so it snaps to the nearest one at or before your specified start time. If frame-accurate trimming is critical, you would need to re-encode the output (removing `-c copy` and specifying explicit codec flags like `-c:v msmpeg4 -b:v 2000k -c:a wmav2 -b:a 128k`), which takes longer and introduces a small amount of quality loss.
Yes. The output remains a valid ASF container with an msmpeg4 video track and wmav2 audio, which is exactly what Windows Media Player expects from a WMV file. The `-f asf` flag ensures the container is written correctly as ASF. No metadata that would break WMP playback is introduced or removed during the trim.
Modify the values after `-ss` (start time) and `-to` (end time) in the command. Both accept `HH:MM:SS` format or plain seconds — for example, `-ss 00:01:30 -to 00:03:45` trims from 1 minute 30 seconds to 3 minutes 45 seconds. Alternatively, replace `-to` with `-t` followed by a duration in seconds if you want to specify how long the clip should be rather than where it ends.
The command as shown processes a single file, but you can wrap it in a shell loop for batch processing. On Windows Command Prompt: `for %f in (*.wmv) do ffmpeg -i "%f" -ss 00:00:00 -to 00:00:10 -c copy "trimmed_%f"`. On Linux or macOS bash: `for f in *.wmv; do ffmpeg -i "$f" -ss 00:00:00 -to 00:00:10 -c copy "trimmed_$f"; done`. Adjust the timestamps to your desired trim range.
FFmpeg generally copies ASF metadata (such as title, author, and copyright tags) when stream-copying a WMV file, but some WMV-specific ASF header attributes may be dropped or not fully preserved depending on how the original file was authored. DRM licensing information embedded in a protected WMV file will not be transferred to the output — this tool only works correctly on DRM-free WMV files.
Technical Notes
WMV files use the ASF (Advanced Systems Format) container, which is why the `-f asf` flag is required to ensure FFmpeg writes a properly structured output rather than inferring the format ambiguously. The default video codec for WMV in this tool is msmpeg4 (Microsoft MPEG-4 Version 3), a lossy proprietary codec distinct from standard MPEG-4 — it is not interchangeable with libx264 or other modern codecs without full re-encoding. The audio is handled by wmav2, Microsoft's second-generation Windows Media Audio codec. Since WMV does not support subtitle tracks or chapter markers, none of that metadata is relevant to this trim operation. Multiple audio tracks are technically supported by the ASF container, and `-c copy` will preserve all of them in the output. One important limitation: the ASF keyframe index may not be dense enough for sub-second precision trimming without re-encoding, which is inherent to how WMV files are structured rather than a limitation of FFmpeg or this tool.