The hlv file extension is associated with multimedia file format (probably video encoded with H.263 codec) that is used by unspecified Chinese multimedia software or devices, like digital audio players.
HLV format seems to be obsolete, it is not supported by known current multimedia players and devices.
How to open:
Possibly some older media players could playback this files, but we do not know about any recent ones.
How to convert:
As far as we know, this .hlv 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.