Progressive segmented frame

Description

Progressive segmented Frame (PsF) is a High Definition video format used to store progressive content on interlaced media.

Each progressive frame is segmented into two interlaced fields without interfield motion, or "combing". PsF is an alternative to telecine, wherein certain frames are "pulled down" across multiple fields, resulting in output with a different frame rate.

Use

Motion picture film cameras produce progressive images, usually at 24 frames per second. In order to display those images on NTSC television, whose framerate is 29.97 frames per second interlaced (59.94 fields per second), each frame must be split into alternating groups of 3 and 2 fields. This is knowns as 3:2 pulldown.

Certain high definition tape formats, such as HDCAM allow frame rates other than 29.97. It is therefore possible, using PsF, to store "true" 24 frames per second progressive images without pulldown, which then play back at the original framerate. Thus the 24PsF and 23.976PsF (for compatibility with NTSC) formats were devised, which exist on tape as 48 (or 47.952) fields per second interlaced. When set up correctly, a progressive scan monitor will read these interlaced fields two at a time, and display each pair as a single progressive frame, temporally identical to the source. PsF content can also be played back on interlaced displays, but the image will flicker.

Sony's CineAlta series of cameras are capable of recording directly to 23.976PsF and 24PsF on HDCAM tape.