DS90UB960-Q1: Camera's Maximum frame rate calculation question

Hello Merlyn,

Please see 960 datasheet section 7.4.20 which describes how to do a detailed calculation of CSI-2 aggregation bandwidth. The calculation is a little bit more complex than what was stated your question because an aggregated CSI-2 output carrying multiple virtual channels has additional overhead from packet boundary separation which needs to be considered. The method would be to do this:

Calculate Input bandwidth sum for all 4 sensors which requires knowledge of the horizontal active pixels per line, color depth, FPS, and total vertical lines per frame (including vertical blanking):

Input BW = (Hactive * bits per pixel)/Line time

Where Line time = 1/(FPS*Vertical Total Lines)

ex. 

Sensor active = 1920x1080

Sensor total (including blanking) = 2100x1296

Bpp = 16

FPS = 36.16

Input BW = ~1.44Gbps per camera

Sum of Input BW = ~5.76Gbps

Next you must calculate the output bandwidth with Equation 1 or Equation 2 in the 960 datasheet. For example:

Forwarding mode = Round Robin 

NCSI Lanes = 4

fCSI = 1.6GHz 

Clock mode = Continuous 

tCSI_Overhead = 0.76us

Output BW = ~5.53Gbps

So in this example aggregating these 4 cameras would probably not be viable in round robin mode, but may be feasible in synchronized line-concatenated mode (since the output bandwidth will be higher). To get accurate calculations you need the Vtotal or line time for each sensor. 

Also please note that these calculations for output BW only hold when the input sensors are identical to eachother (same video parameters). If the sensors have different line lengths, number of pixels per line, frame rate, etc. then the output BW calculation becomes much more complex. We are working on a training video for this topic later in the year. 

Best Regards,

Casey 

Thank you for your help, and I think  an excel file to do these calculations may be eazier to use.