The file uses "boxes" or "atoms" to organize data. For example, the ftyp box identifies the file type, while the mdat box contains the actual media.
Many dashcams and security systems use a "G" prefix followed by a number to denote folders or groups, with sequential numbers for individual video clips. g4_0156.mp4
In professional video editing or development (such as game design), "g4" could refer to a specific project phase (Gate 4 or Gen 4) or a particular asset category. General Information on MP4 Files The file uses "boxes" or "atoms" to organize data