Calculate FX3/CX3 latency in Video Streaming Design - KBA223271

Version 4

    Version: **

     

    Translation - Japanese: ビデオストリーミングデザインでのFX3/CX3のレイテンシ計算 - KBA223271 - Community Translated (JA)

     

    Question:

    How can we roughly calculate the latency introduced by FX3/CX3 in the video streaming design?

     

    Answer:
    The latency can be estimated roughly using the information in the following table.

    Device

    MIPI Block

    FX3 48KB Buffer Filling Time

    USB (~ 300 MBps)

    Total Latency

    FX3

    NA

    614.4 µs

    48KB/300=160 µs

    774.4 µs

    CX3

    30us

    614.4 µs

    48KB/300=160 µs

    804.4 µs

    The results in this table are obtained based on the following:

    • CX3: input:1080p@30 fps, RAW10 output: USB3.0. The latency time is the time between the input and the output in this case.
    • FX3: input:1080p@30 fps, 32-bit parallel output: USB3.0. The latency time is the time between the input and the output in this case.

    Note:

    1. We considered 1080p@30 fps for calculation in this case. Each line will take 33.33ms / 1080=30μs.  
    2. The number of lines for the 48-KB buffer should be (48*1024) / (1920*10/8) = 20.48
    3. Buffer filling time should be line time* No. of lines in a buffer =  30*20.48=614.4μs

    For other resolutions, frame rates, and buffer size configuration, the results are different. However, it can be calculated in the same way as shown above.