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DS90UB953-Q1: 4K@30fps video stream support over SerDes

Mohbbat Singh
Prodigy 20 points
Part Number: DS90UB953-Q1
Other Parts Discussed in Thread: DS90UB935-Q1

Hi Team,

As per our requirement, we have to use 4K@30fps image sensor (having 4 lane MIPI-CSI2) with DS90UB953&DS90UB954 SerDes link.

Could you please let us know, Is it feasible to stream 4K@30fps video stream using DS90UB953&DS90UB954 SerDes link?

Regards,

Mohabbat Singh

  • 0
    TI__Mastermind 28510 points

    Hello Mohabbat,

    It depends on the full camera configurations. The 953 serializer can support up to 3.328Gbps of video throughput received from a camera/imager. Each MIPI CSI-2 data lane on the 953 supports up to 832Mbps of data transfer and up to four lanes can be routed from the camera to the RX Port on the 953.

    The total video throughput of the image sensor can be calculated using the following equation:

    Video Throughput = HActive x VActive x (Frame Rate) x Bits-Per-Pixel x Overhead(Assume 25% if unknown)

    If you use this equation to calculate the video throughput of the image sensor and it is less than 3.328Gbps, then the 953/954 devices can be used. If the image sensor's calculated video throughput is more than the video throughput that is supported on the 953 device and it is not possible to lower other imager settings to reduce the video throughput, then I recommend contacting a local TI sales to find out more about our 97x NDA line of serializer/deserializer products, which can support much higher video bandwidths and can easily support your 4K@30fps sensor application.

    Best,

    Justin Phan 

  • 0 in reply to Justin Phan
    Prodigy 20 points

    Hi Justin,

    Thanks for your feedback.

    I think this 25% overhead for the Blanking of the Image sensor and, we must assume overhead for SerDes link as per below note that I have found on e2e forum:

    "Need to add the Blanking (approx. 15-30%) of the Image sensor. So it would be: 3840x1080x10x60x1.25= 3.11Gbps. This is the pure CSI throughput coming out of the image sensor into the SER. For calculating the line rate over the FPD-Link you should add approx. 25% overhead."

    Please let us know your thought on this.

    As 953 serializer can support up to 3.328Gbps throughput as per ideal theoretical calculation, so please help to provide your thoughts on below points:

    1. What will be maximum throughput it 953&954 (From Ser Input to Des output) can support practically?
    2. What achievable throughput % of maximum throughput (3.32Gbps), we need to consider for proper data transmission from Ser input to Des output?

    As per datasheet of 953 and 954, they are 4.16-Gbps grade serializer supports high-speed sensors including full HD 1080p 2.3MP 60-fps and 4MP 30-fps imagers.

    So if we calculate the vedio throughput for 4MP 30-fps 10 bit then it comes arround:

    = 2560 x 1440 x 30 x 10 x 1.25 (25% Blanking) x 1.25 ( 25% SerDes Overhead)

    = 1,728,000,000 = 1.72 Gbps which is the the ~55% of 3.32Gbps(Max supported throughput of 953)

    Regards,

    Mohabbat Singh

  • 0 in reply to Mohbbat Singh
    TI__Mastermind 28510 points

    Hello Mohabbat,

    The video throughput calculation does not include an extra parameter to estimate blanking. In terms of the supported technical specs of the 953, you just need to consider the active video and the CSI-2 overhead, which is extra signal bandwidth that is caused by the CSI-2 packet header, footer, and LPS surrounding the actual video data that is being transmitted.

    Here is a figure pulled from the 953 datasheet:

    The below calculation is correct in calculating the Video Throughput of the connected camera/imager, which needs to be less than the supported technical specs of the 953 (3.328Gbps if 4 CSI-2 data lanes are used).

    Video Throughput = HActive x VActive x (Frame Rate) x Bits-Per-Pixel x Overhead(Assume 25% if unknown)

    Using the given specs that you gave, the Video Throughput is calculated below:

    Video Throughput = 2560 x 1440 x 30 x 10 x 1.25

                                    = 1.3824 Gbps

    The 953 can support the video throughput of your camera application. The lower-spec 935 device can also support your application, since it supports up to 2.528Gbps of video throughput.

    Best,

    Justin Phan

  • 0 in reply to Justin Phan
    Prodigy 20 points

    Hi Justin,

    Could you explain the math for 2.528Gbps of video throughput?

    Regards,

    Mohabbat Singh

  • 0 in reply to Mohbbat Singh
    TI__Mastermind 28510 points

    Hello Mohabbat,

    The DS90UB935-Q1 is a lower-spec version of the 953 device, which supports a Video Throughput of up to 2.528Gbps, as defined in the 935 datasheet:

    This means that if the connected camera/imager uses four CSI-2 data lanes, then each data lane can only operate at up to 632Mbps. If you only have two data lanes routed between the imager and serializer, then you can send video data at rate of 832Mbps, since the maximum total video throughput will still be below the rated 2.528Gbps.

    Best,

    Justin Phan