Video Format knowledge

I. Standardized image format

The following describes the parameters of the five CIF image formats. Parameter order: "number of pixels for brightness sampling in image format (dx) number of rows for brightness sampling (dy)

Number of pixels in the color sampling (dx/2) the number of rows in the color sampling (dy/2 )".

Sub-qcif 128x96 64 48

Qcif 176x144 88 72

CIF 352x288 176 144

4cif 704x576 352 288 (D1)

16cif 1408x1152 704 576

Qcif stands for quarter common intermediate

Format. Qcif is a common standard image format. In the H.323 protocol cluster, the standard resolution of the video collection device is defined. Qcif = 176x144 pixels.

CIF is a commonly used standard image format (Common intermediate format ). In the H.323 protocol cluster, the standard resolution of the video collection device is defined. The CIF = 352 × 288 pixel CIF format has the following features:

(1) the spatial resolution of TV images is the resolution of the home video system (VHS), that is, 352 × 288.

(2) Use non-interlaced scan ).

(3) When NTSC frame rate is used, the maximum frame rate of TV images is 30 000/1001 ≈ 29.97 frames/second.

(4) use a horizontal resolution of 1/2 pal, that is, 288 lines.

(5) The brightness and two color difference signal (Y, CB and Cr) components are encoded, their value range is the same as the ITU-R

Bt.601. That is, black = 16, white = 235, the maximum color difference is 240, and the minimum value is 16.

Currently, the monitoring industry mainly uses qcif (176 × 144), CIF (352 × 288), half D1 (704 × 288), and D1 (704 × 576) resolutions, the resolution of CIF videos is mainstream, and most products adopt the resolution of CIF videos. Currently, the market accepts the CIF resolution for four main reasons: 1. Currently, digital monitoring requires that the video stream not be too high; 2. Video transmission bandwidth is also limited; 3. halfd1 and D1 resolution can improve clarity and meet high quality requirements, but at the cost of high code streams. At this stage, a large number of D1 products have emerged, but the market share is very small. 4. The CIF resolution is adopted, and the signal-to-noise ratio is above 32 dB. This is acceptable for general users, but it is not ideal for video image quality. Currently, industry insiders are trying to use half D1 to find a balance between CIF and D1. However, as the capacity of a single hard disk reaches 1000 GB or even GB, most of the DVRs in China can connect eight GB hard disks, so D1 will gradually become the mainstream.

What is the dcif resolution?
After research, it is found that a more effective monitoring video encoding resolution (dcif), its pixel is 528 × 384. Dcif resolution indicates that the origin of the video image is
Odd and even half
D1, which is transformed by the anti-barrier to form a D1 (720*576). D1 is used as the border processing and changed to 4cif (704 × 576). The 4cif is scaled down by the horizontal 3/4 and the vertical 2/3.
To narrow down and convert it to 528x384. 528x384, the number of bytes is exactly twice the number of CIF bytes. to distinguish it from the common 2 CIF (704x288), we call it d.
Ouble CIF, or dcif for short. Obviously, dcif is more balanced in both the horizontal and vertical directions than half D1.

What is D1?

D1 is the standard for digital TV system display formats. It can be divided into the following five types:

D1: 480i format (525i): 720 × 480 (horizontal 480 line, interlace scan), the same as NTSC analog TV definition, line frequency is 15.25 kHz, equivalent to what we call 4cif (720x576)

D2: 525 P format (720 p): 480 × 480 (horizontal 31.5 lines, row-by-row scan), which is much clearer than D1 line-by-row scan and has the same specifications as line-by-row scan for DVD. The line frequency is kHz.

D3: 1080i format (1125i): 1920x1080 (horizontal 1080 line, interlace scan), HD relaxation adopts the most resolution, the resolution is 1920 x 1080i/60Hz, the line frequency is 33.75 kHz.

D4: 750 p (1280 p): 720 × 720 (horizontal lines, row-by-row scan). Although the resolution is lower than D3, more people on the market feel that the visual effect is clearer than that of 1080i (the actual 540 lines. However, in my opinion, when the maximum resolution is 1920 × 1080, D3 is clearer than D4, especially in terms of text expressiveness, with a resolution of 1280 × 720 p/60Hz, the line frequency is 45 kHz.

D5: 1125 P format (1920 P): 1080 × 1080 (horizontal 1920 lines, row-by-row scan). Currently, the highest standard for HD videos for civilian use is 1080 × P/60Hz, the frequency is 67.5 kHz.

Among them, the D1 and D2 standards are the highest standards for analog TV, which cannot be called high definition. The D3 1080i standard is the basic standard for High Definition TV, and it can be compatible with the 720p format, the 1080p of D5 is only a professional standard, not a civil level. The above 60Hz is only an ideal field frequency, and its line frequency is 67.5 kHz, at present, there is no TV with such high frequency. In practice, the field frequency of P in the professional field is only 24Hz, 25Hz and 30Hz.

It should be pointed out that the D terminal is a special interface unique to Japan. Domestic TVs have almost no such interface, and the most is the chromatic aberration interface, while the chromatic aberration interface supports up to D4, in theory, there is certainly no high definition of HDMI (a pure digital signal that supports up to 1080 p), but there is generally no big difference in the resolution of 1920: 1080.

What is the dcif resolution?

After research, it is found that a more effective monitoring video encoding resolution (dcif), its pixel is 528 × 384. Dcif resolution indicates that the origin of the video image is to convert the odd and even half D1 into a D1 (720*576) by the reversed line. D1 is used for border processing, to 4cif (704x576), 4cif reduced by horizontal 3/4, vertical 2/3, and converted to 528x384. the number of CIDR blocks of 528 × 384 is exactly twice the number of CIDR blocks. to distinguish it from the common 2cif (704*288), we call it double CIF, or dcif for short. Obviously, dcif is more balanced in both the horizontal and vertical directions than half D1.