24p

In video technology, 24p refers to a video format that operates at 24 frames per second (typically, 23.976 frames/s when using equipment based on NTSC frame rates) frame rate with progressive scanning (not interlaced). Originally, 24p was used in the non-linear editing of film-originated material. Today, 24p formats are being increasingly used for aesthetic reasons in image acquisition, delivering film-like motion characteristics. Some vendors advertise 24p products as a cheaper alternative to film acquisition.

When working entirely within the digital non-linear domain, 24p material is more easily handled than material of higher frame rates. 24p material requires care when it is processed using equipment designed for standard video frame rates.

There are two common workflows for processing 24p material using video equipment, one using PAL frame rates, and the other using NTSC frame rates. Of these two, the PAL route is the simpler, but each has its own complications.

24p material can be converted to the PAL format with the same methods used to convert film to PAL. The most popular method is to speed up the material by 1/24 (~4.1%). Each 24p frame will take the place of two 50i fields. This method incurs no motion artifacts other than the slightly increased speed, which is typically not noticeable. As for audio, the ~4% increase in speed raises the pitch by 0.7 of a semitone, which again typically is not noticed. Sometimes the audio is pitch shifted to restore the original pitch.

If 24p footage cannot be sped up, (for example if it were coming through a live NTSC or HD feed) it instead can be converted in a pattern where most frames were held on screen for two fields, but every half second a frame would be held for three fields. Thus the viewer would see motion stutter twice per second. This was the common result when programs were shot on film or had film portions, edited on NTSC, and then shown in PAL countries (mostly music videos). NTSC to PAL conversion also tends to blur each film frame into the next, and so is seen as a sub-optimal way to view film footage.

...
Wikipedia