COMMON INTERMEDIATE FORMAT

(Redirected from QCIF)
'CIF' (''Common Intermediate Format'') is used to standardize the horizontal and vertical resolutions in pixels of YCbCr sequences in video signals. It was designed to be easy to convert to PAL or NTSC standards. It was first proposed in the H.261 standard. It defines a video sequence with a resolution of 352×288, a framerate of 30000/1001 (roughly 29.97) fps, with colour encoded using YCbCr .
'QCIF' means "Quarter CIF". To have one fourth of the area as "quarter" implies, height and width of the frame are halved.
Terms also used are 'SQCIF' (Sub Quarter CIF), '4CIF' (4× CIF) and '16CIF' (16× CIF). The resolutions for all of these formats are summarized in the table below.

Format	Video Resolution
SQCIF	128 × 96
QCIF	176 × 144
CIF	352 × 288
4CIF	704 × 576
16CIF	1408 × 1152

xCIF pixels are not square: xCIF formats have 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 x 288 square pixels.
The CIF "image sizes" were specifically chosen to be multiples of macroblocks (i.e. 16x16 pixels) due to the way that Discrete cosine transform based video compression/decompression is handled. So, by example, a CIF-size image (352x288) corresponds to 22x18 macroblocks.

Contents

References

See also

References

★ ITU-T H.261 standard [1]

See also

★ H.261

★ H.263

★ H.264

★ List of common resolutions

★ DVB

★ DVD

★ HDTV

★ VCD

★ Source Input Format