Common Intermediate Format

CIF (Common Intermediate Format or Common Interchange Format), also known as FCIF (Full Common Intermediate Format), is a format used to standardize the horizontal and vertical resolutions in pixels of YCbCr sequences in video signals, commonly used in video teleconferencing systems. It was first proposed in the H.261 standard.

CIF was designed to be easy to convert to PAL or NTSC standards. CIF defines a video sequence with a resolution of 352 × 288 like PAL Source Input Format, a framerate of 30000/1001 (roughly 29.97) frames like NTSC, with colour encoded using YCbCr 4:2:0.

QCIF means "Quarter CIF". To have one quarter of the area, as "quarter" implies, the height and width of the frame are halved.

Terms also used are SQCIF (Sub Quarter CIF, sometimes subQCIF), 4CIF (4× CIF) and 16CIF (16× CIF). The resolutions for all of these formats are summarized in the table below.

xCIF pixels are not square, instead having a native aspect ratio of ~1.222:1. On older television systems, a pixel aspect ratio of 1.2:1 was the standard for 525-line systems (see CCIR 601). On square-pixel displays (computer screens, many modern televisions) xCIF rasters should be rescaled horizontally by ~109% to 4:3 in order to avoid a "stretched" look: CIF content expanded horizontally by ~109% results in a 4:3 raster of 384 × 288 square pixels.