The gmm file extension is related to the Global Mobile Media.
Compressed media file using the proprietary compression technology HVMT (High-quality Video Media Technology) designed for IPTV use on PCs as well as mobile phones.
How to open:
Use GMT Player to work with *.gmm files.
How to convert:
As far as we know, this .gmm file type can't be converted to any other file format. This is usually the case of system, configuration, temporary, or data files containing data exclusive to only one software and used for its own purposes. Also some proprietary or closed file formats cannot be converted to more common file types in order to protect the intellectual property of the developer, which is for example the case of some DRM-protected multimedia files.