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Yixun Liu

Hi,

I am confused for the example located at

librealsense/examples/pose-and-image/.

As pointed by the overview of this example:

"This sample demonstrates streaming pose data at 200Hz and image data at 30Hz using an asynchronous pipeline configured with a callback"

I am wondering how the pose data can have higher rate than the rate of the image since the pose estimation should be based on the image data?

Thanks.

Yixun

 

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3 comments

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  • MartyX Grover

    Hi Yixun Liu  That particular example is for the RealSense T265 Tracking Camera model only.  This model has built-in support for 6DOF (6 Degrees of Freedom) pose stream data that the 400 Series camera models do not have.  

    Quoting about 6DOF pose data support from the Intel guide at the link below:

    https://www.intelrealsense.com/how-to-getting-imu-data-from-d435i-and-t265/

    "The T265 tracking camera utilizes the same IMU sensor as the D435i.  However, unlike the D435i, which delivers the raw IMU data directly to the host PC, the T265 redirects IMU readings into an Intel Movidius Myriad 2 Vision Processing Unit (VPU).  The inertial sensor data is also complemented by video from two fisheye monochrome sensors that are fed into the VPU as well.  The VPU employed with T265 is capable of fusing inertial and video sensors to produce a reliable and persistent six degrees of freedom (6DOF) pose, offloading the CPU-intensive calculations from the host PC".

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  • Yixun Liu

    Hi MartyG,

    Thanks for your response.

    Actually I know this example is for T265. My question is since T265 fuses the information from the IMU and the two fisheye sensors to obtain the 6DOF pose, the pose rate should be limited to the rate of the fisheye sensor. How could it be as higher as 200Hz?

    Best,

    Yixun

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  • MartyX Grover
    • Edited

    My understanding is that this example uses asynchronous processing via callbacks and so the frame processing takes place outside of the wait_for_frames() loop. 

     https://github.com/IntelRealSense/librealsense/issues/3817#issuecomment-485663496

    Asynchronous versus synchronous is described in the opening paragraph of the link below.

    https://github.com/IntelRealSense/librealsense/wiki/Frame-Buffering-Management-in-RealSense-SDK-2.0

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