Free online USM to WEBM converter

What the USM format is

USM is a container associated with CRI Middleware's Movie 2 system, widely used for cutscenes, menus, advertisements, and other video assets in console and PC games. Game publishers typically create USM files with CRI's encoding tools, and the files may contain MPEG-2-derived video plus CRI audio such as ADX or HCA.

Many USM files are encrypted or packaged with game-specific metadata. The .usm extension alone does not identify a universally supported codec, so FFmpeg and ordinary media players may fail to open the file. A compatible USM demultiplexer or decrypter is normally required before encoding it as WEBM.

What the WEBM format is

WEBM is a Matroska-based container intended primarily for web video. Its usual codecs are VP8 or VP9 for video and Vorbis or Opus for audio. Chromium-based browsers, Firefox, and many HTML5 video players support WEBM without additional plugins.

WEBM is useful when a video must be embedded in a web page, uploaded to a service that accepts open web codecs, or edited in software that does not understand CRI's USM container. VP9 generally produces smaller files than VP8 at similar quality, while Opus is the usual choice for modern audio.

How to actually convert USM to WEBM

Option 1: use the built-in online converter

You can try converting the file on 101convert.com for free without installing software. Upload the USM file, choose WEBM as the output format, start the conversion, and download the result. This works only when the converter can recognize and decode that particular USM variant; encrypted game files may require local extraction first.

Option 2: extract the USM, then encode with FFmpeg

1. Make a backup of the original video.usm. Do not overwrite it because extraction tools may produce several streams or intermediate files.
2. Open the file with a USM-capable utility such as USMTool or the relevant USM extraction function in VGMToolbox. Use the tool's decrypt or demultiplex operation and save the extracted streams to a separate directory.
3. Inspect the output. A video stream may be written as video.m2v; audio may be .adx, .hca, or another CRI-specific format. If the audio is ADX or HCA, decode it with a compatible CRI audio utility or vgmstream build and produce audio.wav.
4. Install FFmpeg and encode the extracted streams. For broad browser compatibility, use VP9 and Opus:

ffmpeg -i video.m2v -i audio.wav -map 0:v:0 -map 1:a:0 -c:v libvpx-vp9 -crf 32 -b:v 0 -c:a libopus -b:a 128k -shortest output.webm

The -crf value controls VP9 quality; lower values produce better quality and larger files. A value around 28–35 is a practical starting range. If the extracted video already has a browser-compatible codec, you can avoid video re-encoding with -c:v copy, but most USM video streams are not suitable for direct copying into WEBM.

If the source has no audio, omit the second input and audio mapping:

ffmpeg -i video.m2v -c:v libvpx-vp9 -crf 32 -b:v 0 output.webm

Quality, compatibility, and limitations

USM extraction and WEBM encoding are separate operations. A conversion program that cannot decrypt or demultiplex the original USM cannot recover its video merely by changing the file extension. Some games use encryption keys or custom packaging that requires the correct title-specific tool or key.

Re-encoding from MPEG-2-derived game video to VP9 or VP8 causes generation loss. Keep the original USM and extracted streams as archival sources, and use a lower CRF only when the WEBM output shows visible blocking or fine-detail loss. Check the result with ffprobe output.webm or a media player, especially for missing audio, incorrect duration, interlacing, or audio/video synchronization.

If the source is interlaced, deinterlace during encoding with a filter such as -vf yadif. If the source has unusual frame timing, preserve timestamps during extraction and test the complete output rather than judging only a short preview.