Compress WTV Online — Free File Size Reducer
Compress WTV recorded TV files by re-encoding the video stream with H.264 at CRF 23 and audio with AAC at 128k — dramatically reducing file size while keeping the recording playable in Windows Media Center and compatible DVR software. WTV files from broadcast recordings can be enormous; this tool lets you shrink them in-browser without uploading a single byte to a server.
to
FFmpeg Command
Copy this command to run the same conversion locally with FFmpeg on your desktop. Download FFmpeg
Drop your WTV file here
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Settings
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
WTV files produced by Windows Media Center typically contain MPEG-2 video and AC-3 (Dolby Digital) audio captured directly from a broadcast signal, resulting in very large files. This compression tool re-encodes the video stream using the H.264 codec (libx264) at CRF 23 — a perceptually transparent quality level that produces significantly smaller files than the original MPEG-2 broadcast stream. The audio is simultaneously transcoded from AC-3 to AAC at 128k bitrate, which is efficient and broadly compatible. The output retains the WTV container, preserving compatibility with Windows Media Center metadata, embedded program guide information, and multiple audio track structures. Because both video and audio are fully re-encoded (not remuxed), processing time is longer than a simple container swap, but the file size reduction is substantial — often 50–70% smaller than the original broadcast recording.
What Each Flag Does
| Flag | What it does |
|---|---|
ffmpeg
|
Invokes the FFmpeg program, the open-source multimedia processing engine that powers this conversion. In the browser, this runs as FFmpeg.wasm via WebAssembly. |
-i input.wtv
|
Specifies the input file — your original WTV broadcast recording from Windows Media Center. FFmpeg reads the MPEG-2 video, AC-3 audio, subtitle, and metadata streams from this container. |
-c:v libx264
|
Selects the H.264 video encoder (libx264) to re-encode the video stream. This replaces the original MPEG-2 broadcast video with a far more space-efficient H.264 stream while preserving the WTV container structure. |
-crf 23
|
Sets the Constant Rate Factor for H.264 encoding to 23, which is FFmpeg's default and produces visually transparent quality for most broadcast TV content at a fraction of the MPEG-2 bitrate. Lower values (e.g., 18) increase quality and file size; higher values (e.g., 28–35) reduce file size with more visible compression. |
-c:a aac
|
Transcodes the audio stream to AAC, replacing the original broadcast audio (typically AC-3/Dolby Digital). AAC is efficient and broadly compatible, and is the default audio codec for this WTV output configuration. |
-b:a 128k
|
Sets the AAC audio bitrate to 128 kilobits per second, a standard quality level suitable for stereo TV audio that produces clean, artifact-free sound for dialogue and broadcast content. |
output.wtv
|
Specifies the output file as a WTV container, ensuring the compressed recording remains in the Windows Television format and stays compatible with Windows Media Center, Windows Media Player, and other WTV-aware software. |
Common Use Cases
- Shrinking large Windows Media Center DVR recordings of sports events or movies to free up hard drive space on a Windows Home Server or media PC
- Compressing a WTV broadcast recording before archiving it to an external drive or NAS, where the original MPEG-2 bitrate wastes too much space
- Reducing the file size of a recorded TV episode to make it easier to copy over a home network to another Windows machine running Windows Media Center
- Batch-preparing a library of old Windows Vista or Windows 7 Media Center recordings for long-term storage by converting them to a more space-efficient H.264 WTV file
- Compressing a WTV recording of a live broadcast event (news, concert, sports) that was captured at a high broadcast bitrate to a more manageable size for review and clipping
- Producing a smaller WTV file from a dual-audio or SAP broadcast recording while retaining both audio tracks for bilingual playback in Media Center
Frequently Asked Questions
Yes, the output remains a WTV container, which Windows Media Center recognizes natively. However, Windows Media Center's playback compatibility with H.264-encoded WTV files depends on your system's installed codecs and Windows version. On Windows 7 and later with the Media Feature Pack installed, H.264 inside WTV plays back correctly. If you encounter issues, installing a DirectShow codec pack or using Windows Media Player with the right filters can resolve them.
Original WTV recordings from over-the-air or cable broadcasts are typically encoded in MPEG-2 at 10–20 Mbps or higher. Re-encoding to H.264 at CRF 23 usually achieves equivalent visual quality at 2–5 Mbps, resulting in file size reductions of 60–80% for typical broadcast content. A 4GB recording of a one-hour TV show could compress down to 800MB–1.5GB without a noticeable quality difference on a standard display.
The WTV container supports embedded metadata such as show title, episode description, channel, and recording date. FFmpeg attempts to carry over supported metadata tags when writing the output WTV file, but some WTV-specific metadata fields tied to the Windows Media Center database (such as series links or parental ratings stored outside the file) are not embedded in the stream and will not be affected either way. Core descriptive metadata embedded in the file itself is generally preserved.
Most WTV broadcast recordings contain AC-3 (Dolby Digital) audio from the original broadcast signal. The tool re-encodes audio to AAC at 128k because AAC is the default audio codec specified for this WTV output configuration and offers good quality at lower bitrates. If you prefer to keep AC-3 audio or copy the original audio stream without re-encoding, you can modify the FFmpeg command to use '-c:a copy' (if the source is already AC-3 and your WTV player supports it) or '-c:a ac3 -b:a 192k' to retain Dolby Digital encoding.
The CRF value in the command controls the quality-to-size tradeoff for H.264 video. Lower CRF values produce higher quality and larger files (CRF 18 is near-lossless for most content), while higher values produce smaller files with more compression artifacts (CRF 28 or 35 is suitable for content you only need to watch once). To change it, modify '-crf 23' to your desired value, for example: 'ffmpeg -i input.wtv -c:v libx264 -crf 28 -c:a aac -b:a 128k output.wtv' for more aggressive compression. Audio bitrate can similarly be adjusted by changing '-b:a 128k' to '96k' for smaller files or '192k' for higher fidelity.
Yes. On Windows, you can use a simple batch script to process all WTV files in a folder: open Command Prompt, navigate to your recordings directory, and run 'for %f in (*.wtv) do ffmpeg -i "%f" -c:v libx264 -crf 23 -c:a aac -b:a 128k "compressed_%f"'. This iterates over every WTV file and outputs a compressed version prefixed with 'compressed_'. On Linux or macOS (useful if your recordings are on a shared drive), use a bash loop: 'for f in *.wtv; do ffmpeg -i "$f" -c:v libx264 -crf 23 -c:a aac -b:a 128k "compressed_$f"; done'.
Technical Notes
WTV (Windows Television) is a container format proprietary to Windows Media Center, introduced in Windows Vista. Source WTV files from DVR recordings typically contain MPEG-2 video at broadcast bitrates (often 8–20+ Mbps) and AC-3 audio, making them among the largest common video file types relative to their duration. This compression operation performs a full transcode: the video is decoded from MPEG-2 and re-encoded as H.264 (libx264) using a constant rate factor of 23, which is FFmpeg's default and represents a good balance between quality and file size for archival purposes. The WTV container supports subtitles (closed captions embedded in the broadcast) and multiple audio tracks (e.g., SAP secondary audio programs for bilingual broadcasts); FFmpeg will attempt to map these through to the output, though subtitle stream compatibility depends on the caption format embedded in the original recording. Chapter markers are not supported in WTV. One important limitation: because this is a lossy-to-lossy transcode (MPEG-2 to H.264), each generation of re-encoding introduces some quality loss. For archival purposes, using CRF 18 or lower preserves more detail. The output WTV file may not be recognized by all third-party media players unless they have proper WTV demuxer support; VLC and MPC-HC handle WTV reasonably well, but native playback is best in Windows Media Player or Media Center on Windows 7/8.