BT.656 interface rate

720p It's a video display format . Letter p Scan line by line （progressive scan）, Numbers 720 In the horizontal direction 720 Scanning lines . Usually 720p The resolution of the picture is 1280×720, Generally, it can also be called HD （HD）. But in some cases , Such as iPod Touch 4, Its 720P Video recording does not mean 1280×720（16:9）, It is 960×720（4:3）, Therefore, it is not indicated that HD Of 720P Filming doesn't always mean 1280×720（16:9）.

     Standard system                     Total scan line     Image area scan line     Total horizontal pixels     Image area horizontal pixels     sampling frequency

    1080P / 60Hz     1125            1080                      2200             1920                         148.5MHz

    1080P / 50Hz     1125            1080                     2640              1920                         148.5MHz

    1080I / 60Hz      1125            1080                     2200              1920                          74.25MHz

    1080I / 50Hz      1125            1080                     2640              1920                          74.25MHz

    720P / 60Hz        750             720                      1650              1280                          74.25MHz

    720P / 50Hz        750             720                      1980              1280                          74.25MHz

The basic concept of digital video comes from analog video . For analog video, we can understand this ：

Video can be decomposed into several basic viewpoints （ Pixels ）, Each pixel has its own color information , On the screen, print out these points by row and column with an electron gun , It forms a complete picture , Continuous shooting , The delay characteristic of human eyes can be used to display “ dynamic ” Image .

Analog bandwidth ： Also known as “ Dot clock ”, Refers to the number of pixels scanned per second , That is, the sum of frequency points displayed on each scan line in unit time , In the analog video with MHz In units of .

for example ,720P/60Hz Analog bandwidth = 1650 * 750 * 60 = 74.25MHz It means that each clock should transmit 74.25M Analog video pixels . Empathy 1080P60 The point clock of is 148.5MHz.

But in digital video, every pixel is made of 3 Two different colors to represent , Each color is transmitted by a certain number of bits , So we usually use bps To represent digital bandwidth , If the RGB transmission , Use... For each color 1 Bytes to output , Then the digital bandwidth of the video is ：

    Digital BandWidth = Analog bandwidth * 8bit * 3 = 1.782Gbps It means to transmit every second 1.782 G Bit data .

                                                                                                    1782 / 24 = 74.25

2640 * 1125 = 2970000 * 50 = 148500000    * 8 * 3 = 3564000000 = 3.564 Gbps

2200 * 1125 = 2475000 * 60 = 148500000