Files with mv3 file extension can generally be found as older audio files. Mostly obsolete and no longer supported in modern programs.
MV3 file extension - Audio data
What is mv3 file? How to open mv3 files?
File type specification:
The mv3 file extension was throughout the past used for several audio formats, including AUPEC (Auckland University Perceptual Entropy Coder) audio or Oozic 3D MusicVideo format.
The AUPEC audio or Oozic 3D MusicVideo format seem to be obsolete without support from developers.
This mv3 file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.