If you are looking for technical information regarding the format itself:

MP4 (MPEG-4 Part 14) is a digital multimedia container format most commonly used to store video and audio, but it can also store other data such as subtitles and still images.

Based on common data structures and naming patterns, "g4_0156.mp4" likely belongs to one of the following:

Researchers often label video files with group codes (e.g., Group 4, Clip 156) for identification in studies involving computer vision, behavior analysis, or forensic video analysis .