Send time stamp data to host without streaming images

abhanupr

Hi,

I have been enjoying working with the OAK-D Pro for a few weeks now. The examples in the doc are really good and easy to follow!

I am also planning to use the on-device programming (https://docs.luxonis.com/en/latest/pages/tutorials/on-device-programming/) for my project to run custom CV code.

Because my application needs to run in real time, I would like to measure the latency of the stereo depth estimation. As I would not be streaming the images to the host in the application, I would like to measure the latency without streaming the ImgFrame object to the host. I thought of using the script node to stream just the timestamp of the ImgFrame of the disparity output so that I could then take the difference of the timestamps of successive frames, so I tried the below python script:

However, I am getting an error when I run it:

UsbSpeed.SUPER

[19443010F1A6992E00] [20.2.4] [1.521] [Script(3)] [critical] TypeError: setData(): incompatible function arguments. The following argument types are supported:

1. (self: lpb.Buffer, arg0: buffer) -> None

Invoked with: <lpb.Buffer object at 0x82762fa0>, datetime.timedelta(seconds=1, microseconds=216140)

At:

<script>(5): <module>

Please could you let me know how to fix this? Also, please suggest if there is a better way of doing it. I have a feeling I am missing something that is simpler.

Best,
AB

jakaskerl

Hi abhanupr
The code you are using should work well. There is also the logs that are sent to the host when using DEPTHAI_LEVEL=TRACE which will tell you how long the stereo took; but might be a bit more difficult, so your approach is totally valid.

Try setting the buffer timestamp to bytearray before passing it to the buffer.

Thanks,
Jaka

abhanupr

Hi jakaskerl

Many thanks for the hint to use bytearray.

I was able to make it work using bytearray and Python struct module. By varying the framerate of the mono cameras I observed that on the OAK-D Pro, depth estimation without too many frame drops can be done up to a framerate of around 105 fps, which is quite impressive! For whoever is interested in such data transfer between host and device, I have attached my code below.

Thanks,
AB