Common Intermediate Format
Encyclopedia
CIF also known as FCIF (Full Common Intermediate Format), is a format used to standardize the horizontal and vertical resolutions
in pixel
s 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 fourth 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 pixel
s 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.
The CIF "image sizes" were specifically chosen to be multiples of macroblock
s (i.e. 16 × 16 pixels) due to the way that discrete cosine transform
based video compression/decompression is handled. So, by example, a CIF-size image (352 × 288) corresponds to 22 × 18 macroblock
s.
SIF (Source Input Format) is practically identical to CIF, but taken from MPEG-1 rather than ITU standards. SIF on 525-Line ("NTSC") based systems is 352 × 240, and on 625-line ("PAL") based systems, it is identical to CIF (352 × 288). SIF and 4SIF are commonly used in certain video conferencing systems.
DCIF means Double CIF, proposed as a compromise resolution between CIF and 4CIF that is more balanced (in terms of horizontal vs vertical resolution) and suited to common CCTV equipment (with 480+ scanlines but a maximum of about 560 TVL
) than 2CIF (704x288). The pixel and therefore data rate is exactly double that of CIFhttp://www.flyancctv.com/en/tech_x.asp?news_id=21, but the 1:1.375 image aspect ratio is a lot closer to standard 4:3, with essentially square pixels.
Image and Video Formats – GIF, TIFF, SIF, CIF, QCIF – Image compression: READ,
JPEG – Video Compression: Principles-I,B,P frames, Motion estimation, Motion
compensation, H.261, MPEG standard
Image resolution
Image resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail....
in pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s of YCbCr
YCbCr
YCbCr or Y′CbCr, sometimes written or , is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the luma component and CB and CR are the blue-difference and red-difference chroma components...
sequences in video signals, commonly used in video teleconferencing systems. It was first proposed in the H.261
H.261
H.261 is a ITU-T video coding standard, ratified in November 1988. It is the first member of the H.26x family of video coding standards in the domain of the ITU-T Video Coding Experts Group , and was the first video codec that was useful in practical terms.H.261 was originally designed for...
standard.
CIF was designed to be easy to convert to PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
or NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
standards. CIF defines a video sequence with a resolution of 352 × 288 like PAL Source Input Format
Source Input Format
Source Input Format defined in MPEG-1, is a video format that was developed to allow the storage and transmission of digital video....
, a framerate of 30000/1001 (roughly 29.97) frames
Frame rate
Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
like NTSC, with colour encoded using YCbCr
YCbCr
YCbCr or Y′CbCr, sometimes written or , is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the luma component and CB and CR are the blue-difference and red-difference chroma components...
4:2:0.
QCIF means "Quarter CIF". To have one fourth 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.
| Format | Video Resolution |
|---|---|
| SQCIF | 128 × 96 |
| QCIF | 176 × 144 |
| SCIF | 256 x 192 |
| SIF(525) | 352 x 240 |
| CIF/SIF(625) | 352 × 288 |
| 4SIF(525) | 704 x 480 |
| 4CIF/4SIF(625) | 704 × 576 |
| 16CIF | 1408 × 1152 |
| DCIF | 528 × 384 |
xCIF pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s are not square, instead having a native aspect ratio of ~1.222:1. On older television systems, a pixel aspect ratio
Pixel aspect ratio
Pixel aspect ratio is a mathematical ratio that describes how the width of a pixel in a digital image compares to the height of that pixel....
of 1.2:1 was the standard for 525-line systems (see CCIR 601
CCIR 601
ITU-R Recommendation BT.601, more commonly known by the abbreviations Rec. 601 or BT.601 is a standard published in 1982 by International Telecommunication Union - Radiocommunications sector for encoding interlaced analog video signals in digital video form...
). 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.
The CIF "image sizes" were specifically chosen to be multiples of macroblock
Macroblock
Macroblock is an image compression component and technique based on discrete cosine transform used on still images and video frames. Macroblocks are usually composed of two or more blocks of pixels. In the JPEG standard macroblocks are called MCU blocks....
s (i.e. 16 × 16 pixels) due to the way that discrete cosine transform
Discrete cosine transform
A discrete cosine transform expresses a sequence of finitely many data points in terms of a sum of cosine functions oscillating at different frequencies. DCTs are important to numerous applications in science and engineering, from lossy compression of audio and images A discrete cosine transform...
based video compression/decompression is handled. So, by example, a CIF-size image (352 × 288) corresponds to 22 × 18 macroblock
Macroblock
Macroblock is an image compression component and technique based on discrete cosine transform used on still images and video frames. Macroblocks are usually composed of two or more blocks of pixels. In the JPEG standard macroblocks are called MCU blocks....
s.
SIF (Source Input Format) is practically identical to CIF, but taken from MPEG-1 rather than ITU standards. SIF on 525-Line ("NTSC") based systems is 352 × 240, and on 625-line ("PAL") based systems, it is identical to CIF (352 × 288). SIF and 4SIF are commonly used in certain video conferencing systems.
DCIF means Double CIF, proposed as a compromise resolution between CIF and 4CIF that is more balanced (in terms of horizontal vs vertical resolution) and suited to common CCTV equipment (with 480+ scanlines but a maximum of about 560 TVL
Television lines
Television lines is a specification of an analog camera's or monitors's horizontal resolution power. It is alternatively known as Lines of Horizontal...
) than 2CIF (704x288). The pixel and therefore data rate is exactly double that of CIFhttp://www.flyancctv.com/en/tech_x.asp?news_id=21, but the 1:1.375 image aspect ratio is a lot closer to standard 4:3, with essentially square pixels.
Image and Video Formats – GIF, TIFF, SIF, CIF, QCIF – Image compression: READ,
JPEG – Video Compression: Principles-I,B,P frames, Motion estimation, Motion
compensation, H.261, MPEG standard
See also
- H.261H.261H.261 is a ITU-T video coding standard, ratified in November 1988. It is the first member of the H.26x family of video coding standards in the domain of the ITU-T Video Coding Experts Group , and was the first video codec that was useful in practical terms.H.261 was originally designed for...
- H.263H.263H.263 is a video compression standard originally designed as a low-bitrate compressed format for videoconferencing. It was developed by the ITU-T Video Coding Experts Group in a project ending in 1995/1996 as one member of the H.26x family of video coding standards in the domain of the ITU-T.H.263...
- H.264
- List of common resolutions
- DVB
- DVDDVDA DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
- HDTVHigh-definition televisionHigh-definition television is video that has resolution substantially higher than that of traditional television systems . HDTV has one or two million pixels per frame, roughly five times that of SD...
- VCDVCDVCD is a three-letter abbreviation with multiple meanings, as described below:* VCD Athletic, semi-professional football team* Video CD* Voice command device* Value change dump * Vocal cord dysfunction* Visual Communication and Design...
- Source Input FormatSource Input FormatSource Input Format defined in MPEG-1, is a video format that was developed to allow the storage and transmission of digital video....