Getting started with video collection and processing (Video resolution Introduction)

Resolution is widely used. Cameras have resolutions, cameras have resolutions, monitors, and printers. Similarly, broadcast TVs and digital videos have resolutions, different fields have different definitions of resolution. Even in the same field, the definition of the same resolution varies according to the standard, for example, D1 resolution, is it 720x316or 720x576? People who are new to video capturing may be confused. This article focuses on definition classification related to broadcast and television and digital videos, this is because video collection and processing basically involve this type of resolution.

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Concept of confusion: Sif and CIF, 4cif and D1

Currently, in the domestic monitoring industry, standard terms for resolution, such as Sif, CIF, 4cif, and D1, are often used in video capture cards, compression cards, and DVR products. In fact, due to the lack of industry standards and standards in the security industry, many terms in the industry come from standards in other industries. Therefore, CIF, Sif, D1, and other words are not only from different sources, even nouns have been confused and confused.

If we look back at the source, the video surveillance industry for security is derived from closed-circuit television (CCTV). Therefore, the standard has always followed the SIF series standard in the TV industry and the D1 standard in the video recorder industry, in the domestic security industry, Sif has been transferred to CIF, and D1 is often confused with concepts such as 4cif and 4sif. A typical phenomenon is that, using CIF and D1 as keywords to search for video capture cards, compression cards, DVRs, and other products, almost all searched for domestic products and domestic export products, only When Sif is used as a keyword can similar foreign products be found. The following describes the series of standards from different origins: CIF, Sif, and D1.

I. CIF

The common intermediate format (common media format), also known as fcif (full CIF), is a standard format used to regulate the pixel resolution of video signals of The YCbCr chromatic aberration component, it is often used in Video Conferencing Systems in the telecom field.

The CIF format is the H.261 video encoding standard (ITU-T H.261) launched by the International Telecommunication Union (ITU) in 1990) the first defined format standard (subsequent improvements to the H.263 series of CIF standards ), it is designed to facilitate interconnection with NTSC and PAL video standards in the TV Industry ([note] SECAM standards and PAL standards are slightly different ), promote interconnection between the telecom and television fields.

To facilitate conversion with the PAL and NTSC formats, because the video size conversion process is easier to zoom in than to zoom in, therefore, the maximum compatibility principle is adopted for definition of the CIF format (larger than the two), and the resolution is 352 × 288 in the same format as that of the palth SIF (source input format, the frame rate is 29.97 FPS (30000 frames/1001 seconds) the same as that of NTSC, and the color space encoding is based on YCbCr.

Qcif indicates "quarter CIF", that is, 1/4 CIF. The resolution width and height are half of the CIF format. sqcif indicates "sub quarter CIF ", the resolution is 4/11 of CIF, 1/3 of CIF, and 4/33 of CIF. Similar formats include 4cif (4 × CIF) and 16cif (16 × CIF ), all are defined based on the CIF format.

The reason why the image size in CIF format is determined to be 352 × 288 is that the macro block (16 × 16 pixels in size) is used in the video compression/decompression algorithm defined in h.261) in fact, the frame of a video in CIF format is composed of 22x18 macro blocks, therefore, the number of pixels per frame is 352 × 288.

It should be noted that the pixels used in the xcif series standards defined by the International Telecommunication Union (ITU) are non-square pixels (for Pixel display ), the x-y ratio of the number of pixels (that is, the storage x-y ratio) is 352: 288 (that is ). Therefore, when xcif series standard videos are displayed on square pixel display devices (calculator display, most hdtv hd Digital TVs, the image needs to be scaled horizontally to 12/11 times (about 109.1%), and the resolution is changed to 384 × 288 (square pixels). The ratio of the number of pixels changes from.

[Note] square pixels are a very important concept, involving video collection, encoding/decoding, transmission, storage, and display, for a detailed explanation of this concept, see the article "square pixel.

Standard Format	Resolution (non-square pixel)	Resolution (square pixel)	Standard Frame Rate (frame/second)
Qcif	176 × 144	192 × 144	29.97 FPS
CIF (fcif)	352 × 288	384 × 288	29.97 FPS
4cif	704 × 576	768 × 576	29.97 FPS
16cif	1408 × 1152	1536 × 1152	29.97 FPS

Ii. Sif

In the MPEG-1 standard launched in 1992, the dynamic image Expert Group (mPEG) first defined SIF (source input format, source input format ), sif is a video format for the storage and transmission of digital videos, commonly used in VCD (MPEG-1 video encoding), DVD (MPEG-2 video encoding) and some video conferencing systems.

Because SIF series standards mainly used in the TV industry, Sif standard formats are divided into SIF-525 (NTSC) and SIF-625 (PAL and SECAM) two types:

(1) 525@59.94Hz SIF format (SIF-525) for NTSC standard, its resolution is 352x240 pixels, refresh frequency (frame rate) is 29.97fps (frame/second)

(2) 625 @ 50Hz SIF format (SIF-625) for PAL and SECAM standard, its resolution is 352 × 288 pixels, refresh frequency (Frame Rate) 25 FPS (frame/second)

Both the SIF-525 and SIF-625 formats fall under the non-line-by-line standard, and the SIF also has a version called SIF-I.

The SIF format video stream is also known as the MPEG-1 ECC (constrained parameters bitstream, constrained parameter code stream ). Compared with the CCIR 601 (also known as ITU-R bt.601/rec.601) digital coding standard defined by the International Telecommunication Union (ITU, SIF can be viewed as the standard in which the CCIR 601 format is halved in terms of frame length, frame width, frame rate, and color.

The dynamic image Expert Group (mPEG), when defining the SIF (source input format) format standard, has referred to the CIF format standard defined by the International Telecommunication Union (ITU, therefore, the SIF standard format is almost the same as the CIF standard format. The difference between the two is that the SIF format is 525 × 352 @ 29.97fps in NTSC standard (240-line, in the PAL/SECAM standard (625-line), it is 352 × 288 @ 25fps, while in the CIF format, there is no standard, the standard format is fixed to 352 × 288 @ 29.97fps (in H.263, the frame rate standard extension supports the equivalent of 7.49fps, 14.99fps, and 59.94fps ).

Because square pixels are widely used in the computer industry, the SIF format (square pixel version) in the computer industry is defined as: resolution 320 × 240 (equivalent to the qvga standard in the computer industry) or 384x288 pixels, the frame rate can be any refresh frequency supported by the computer (60Hz, 75Hz, 85Hz ,......).

[Note] the concept of "square pixel" is the same as above. For details, see http://www.microjie.com/index.php/sionsional-knowledge/82-standards-parterns.

Standard Format	Resolution (non-square pixel)	Resolution (square pixel)	Standard Frame Rate (frame/second)
Sif @ NTSC Standard	352 × 240	320 × 240	29.97 FPS
Sif @ PAL/SECAM Standard	352 × 288	384 × 288	25 FPS
4sif @ NTSC Standard	704 × 480	640 × 480	29.97 FPS
4sif @ PAL/SECAM Standard	704 × 576	768 × 576	25 FPS

 

Iii. D1 (also known as D-1, Sony's D1)

D1 is a professional digital video format standard, mainly used in the digital broadcast and television and video industry. The D1 standard was developed prior to the CIF and SIF standards, as early as 1980s at Sony (Sony) and Bosch-BTS (Bosch-BTS) DVR (digital recorders) the product is used for the first time. In 1986, with the efforts of the SMPTE Engineering Committee, D1 was adopted as the SMPTE standard and mainly used in dvtr products, it is the first mainstream video format in the video industry.

D1 adopts a non-Compressed digital composite video, and the color encoding adopts the CCIR 601 (defined in 1981) YCbCr format, and the audio adopts the PCM format; the audio and video are synchronously stored on a 19mm (3/4 ") Video box. The maximum storage time of the D1 video is 94 MINUTES. The resolution of D1 is defined as 720 × 486 (non-square pixel) in NTSC and 720 × 576 (non-square pixel) in PAL/SECAM ). The early D1 system was complex and difficult to operate. Although it was quickly stabilized later, D1 (in 1986) had its gorgeous image quality (equivalent to SD, standard definition) high price, high configuration requirements, and high upgrade costs.

Standard Format	Resolution (non-square pixel)	Resolution (square pixel)	Standard Frame Rate (frame/second)
D1 @ NTSC Standard	720 × 486	720 × 540	29.97 FPS
D1 @ PAL/SECAM Standard	720 × 576	768 × 576	25 FPS

Iv. Comparison of three series of standards: CIF, Sif, and D1

Standard Format	Standardization time	Standardization Organization	Application fields
D1	1986	Association of film and television engineers (SMPTE)	Broadcast and television, film, and video
CIF	1990	International Telecommunication Union (ITU)	Telecom, network video
Sif	1992	Dynamic image Expert Group (mPEG)	Multimedia (video, VCD, and DVD)

In practical application, the three most confusing formats are 4cif, 4sif of PAL, and D1 of PAL. The main differences between these formats are as follows:

(1) different application fields;

(2) Different standardization organizations have been developed;

(3) The refresh frequency (frame rate) is defined differently;

(4) The resolution varies in non-square pixel mode.

Standard Format	Resolution (non-square pixel)	Resolution (square pixel)	Standard Frame Rate (frame/second)
4cif	704 × 576	768 × 576	29.97 FPS
4sif @ PAL/SECAM Standard	704 × 576	768 × 576	25 FPS
D1 @ PAL/SECAM Standard	720 × 576	768 × 576	25 FPS