The metadata data of NB Frames may be divided into two components. NB refers to "number" and further defines the second portion. In simple terms, NB Frames are the number of frames that are present inside the streaming of the video file like MOV or Mp4 or an audio file, such as AIFF and WAV.
NB Frames usually gives the total number of frames in the entire stream. If the number is not known or cannot be identified typically, it will be given the number zero (zero/null).