Free online USM to AAC converter

USM files usually contain game video and CRI audio streams, while AAC is supported by phones, media players, editors, and streaming workflows. Conversion normally requires extracting the audio from the USM first, decoding its original CRI audio format, then encoding the result as AAC.

What the USM format is

USM is a proprietary CRI Middleware movie container used by video games for cutscenes, menus, trailers, and other in-game video. Files commonly contain a video stream plus CRI audio such as HCA or ADX; they do not normally contain AAC directly.

You may encounter USM files in a game's installation directory, downloadable game assets, modding projects, or extracted console archives. Standard media players and FFmpeg builds generally cannot decode every USM variant because the container and its stream metadata may use CRI-specific formats.

What the AAC format is

AAC is a lossy audio codec supported by modern phones, browsers, media players, video editors, and streaming platforms. At a similar bitrate, it commonly provides better quality than older MP3 encoding, although the conversion cannot restore detail already lost in the original USM audio.

A raw AAC file usually uses the .aac extension and ADTS framing. AAC stored in an MPEG-4 container normally uses .m4a; choose .aac when a program specifically requires an elementary AAC stream.

How to convert USM to AAC

Using a desktop extraction and encoding workflow

1. Make a copy of the original USM file. Do not rename the extension and expect that to convert the content.
2. Extract the streams with a USM-capable utility such as USM Extractor, USM Demuxer, or the relevant USM tool in VGMToolbox. The output may be an HCA, ADX, or another CRI audio file.
3. Decode the extracted audio with vgmstream-cli. For example:
   vgmstream-cli -o audio.wav extracted_audio.hca
   Replace the input filename if the extractor produces an ADX or another format supported by your installed vgmstream build.
4. Encode the decoded WAV as a raw AAC file with FFmpeg:
   ffmpeg -i audio.wav -c:a aac -b:a 192k -f adts output.aac
5. For an MPEG-4 audio file instead, use:
   ffmpeg -i audio.wav -c:a aac -b:a 192k output.m4a

If the USM contains several audio tracks, identify the language or channel track before encoding. Extracting every stream can produce multiple files with generic names, so listen to each one or inspect the extractor's stream listing.

Using the built-in online converter

You can try converting the file for free on the 101convert.com website without installing software. USM support depends on the specific CRI container and codec used by the file; if the site cannot read it, use the extraction workflow above.

Quality and compatibility limitations

USM audio is often HCA, which is already compressed. Converting HCA or ADX to AAC is a second lossy encode, so use the highest practical AAC bitrate; 192 kbps is a reasonable general setting, while 128 kbps produces smaller files and 256 kbps retains more detail.

If the extracted audio is multichannel, preserve it with an AAC encoder and container that support the channel layout. Some devices accept only stereo AAC, in which case use -ac 2 with FFmpeg, but downmixing permanently removes the separate surround channels.

When FFmpeg reports that the USM format is unsupported, that is a demuxing limitation rather than evidence that the file is damaged. Extract the CRI streams first; FFmpeg and vgmstream are normally used after that step.