Introduction to SDI video data stream format (frequency, rate, YUV, EAV, SAV)

SDI Introduction to video format

​ common SDI Video formats mainly include SD-SDI、HD-SDI、3G-SDI Three , Its bit rate increases in turn , It also corresponds to videos with different resolutions and refresh rates .

​ The calculation formula of frequency is ：
$$frequencyrate=That\text{'}s\; okZhouperiodCount\times siteZhouperiodCount\times brushnewrate$$
​ The formula for calculating the rate is ：
$$speedrate=frequencyrate\times positionwide$$
​ With the common 1080P、30fps For example, the sequence diagram of the video , It is mainly composed of three signals H、V、DE. Its effective pixel resolution is 1920x1080, Add the blanking period , Its pixel resolution is 2200x1125, by HD-SDI Format , The formula for calculating the frequency and rate is ：
$$frequencyrate=2200\times 1125\times 30=74.25MHz$$

$$speedrate=74.25\times 20=1.485Gbit/s$$

​ The rates corresponding to common video formats are as follows ：

SDI Image standards	name	rate	Format
SMPTE 259M	SD-SDI	270 Mbit/s, 360 Mbit/s,143 Mbit/s, 177 Mbit/s	480i, 576
SMPTE 292M	HD-SDI	1.485 Gbit/s, and 1.485/1.001 Gbit/s	720p, 1080i
SMPTE 424M	3G-SDI	2.970 Gbit/s, and 2.970/1.001 Gbit/s	1080p60

​ So it corresponds to the general HD-SDI Format clock frequency , If the video frame rate is 60fps, The corresponding baud rate is 148.5Mhz.

SDI Video stream data format

​ The commonly used video stream format is 20-bits SDR Mode, The data format is YUV Format （YUV Format reference ）, The schematic diagram is as follows ：

​ As you can see from the diagram , The bit width of the data stream is 20bits,10-19 Position as Y component ,0-9 Position as UV component ,UV Alternate transmission , Each clock cycle transmits 20bits data , Including a Y And a U/V, And because of the general operation 、 The display digits are 8bit, That is to say 0~255, So we take Y、U/V Component height 8 position .

​ According to SDI The encoding format of , Before the effective pixels 4 Pixels and after 4 Pixels to transmit fixed format data ,3FF000000XYZ, among XYZ stay The period of validity and Blanking period , Before effective pixels and After effective pixels It's all different . among SAV and EAV Is in Before effective pixels / after Of XYZ representative , namely Start and End.

​ Captured by oscilloscope EAV Some video data .

​ XYZ The key word in SAV and EAV And the fixed format of different row numbers are shown in the following figure , After practical operation, it is found that , Of the blanking period SAV by 2AC that will do , Valid for SAV by 200 that will do , The same goes for the hidden period EAV by 2DB that will do , Valid for EAV by 274 that will do .

Sketch Map

​ To sum up, the schematic diagram of video stream data can be obtained as ：

​ The green part is in the blanking period XYZ, Magenta is within the effective pixel period XYZ, The middle is the effective pixels of the video stream , The rest is invalid information .

​ If the pixels in each row within the blanking period and the effective pixels are taken out , Zoom in to get the schematic diagram shown in the following figure ：

​ Compare with the above schematic diagram SDI Signal encoding and decoding .