What is cadence?

In addition to frame rate, video and movie content is often described by a cadence.  In basic terms, this relates to the number of repetitions of a field or frame in a sequence of fields or frames.  Frame repetition has been used since the earliest days of cinema where repeated shutter opening and closing was used to reduce flickering.  When movies began to be transferred for TV viewing in the US, the need to change from 24 fps to 59.94 fps was solved using a scanning pattern of 2 fields then 3 fields, which is termed “2:3 cadence”. 

Interlaced video, being a sequence of odd then even fields (see “What is deinterlacing” above) is termed 1:1.  This denotes that the image is refreshed every field i.e. that there are no repeats.  Many other cadences are in use such as 2:2 (often used to describe progressive segmented frames) and 5:4 (used in animations).