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I can't find the white paper on external synchronization of RealSense depth cameras

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5 comments

  • MartyG

    Hello, the External Synchronization paper has been withdrawn from the white-paper directory.  The reason for this is that its contents were an experimental Proof of Concept that are not validated by Intel.

     


    The original Multi-camera configurations 400 Series hardware synchronization paper that is still available (which covers modes 1 and 2 of the Inter Cam Sync mode) is considered by Intel to be validated and mature.

     


    Whilst the External Synchronization paper is no longer accessible, you can find some images from it that have been quoted as extracts from the paper on other web-pages by performing a Google Images search for the term realsense external synchronization

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  • 1641697053

    Hi MartyG

    Thanks for your detailed reply.

    I'm trying to set Inter Cam Sync Mode in the Intel RealSense Viewer v2.50.0.

    The instruction shows: Inter-camera synchronization mode: 0:Default, 1:Master, 2:Slave, 3:Full Slave, 4-258:Genlock with burst count of 1-255 frames for each trigger.

    I'm puzzled with the usage of "Full Slave" and "Genlock". Could you please explain it to me?

    Now I have a 1Hz PPS signal, which is a 1.8v pulse. And I connect pin5 and pin9 with PPS and GND as instructed. I want to get 20FPS synchronized image stream. What should I set on Inter Cam Sync Mode and Frame Rate (FPS)? I don't find 20Hz in the options of Frame Rate (FPS).

    Thank you for your support,

    Best Regards,

    Jiayuan

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  • MartyG

    In mode 3 (Full Slave), it is meant to sync both depth and RGB timestamps with the master trigger instead of just depth.  In practice though the RGB sync did not work (this paper was an experiment that was not developed any further).

     

    In mode 4+ (genlock, which syncs depth only) a slave camera set to mode 4 or higher that is following the timing of a master trigger will listen indefinitely for a trigger and not initiate capture until it receives it.  In the original slave mode '2' the camera listens for a trigger for a certain time period on each frame and then initiates capture independently (unsynced) if it does not receive a trigger in time.

     

    The trigger frequency should be set to half of the native frequency (the supported RealSense FPS value), as described in the link below.   So you may need to set your camera at 30 FPS and the trigger at 10 Hz (20 / 2).

    https://github.com/IntelRealSense/librealsense/issues/10926#issuecomment-1253773987

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  • 1641697053

    Hi MartyG

    Thank you for your reply. I'm still working with D455. I'm trying to report the local time of the camera to the host computer when it receive a trigger. But I don't want to syncronize it now. Is it possible for the camera to only report the time?

    Best regards,

    Jiayuan

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  • MartyG

    A possible way to report the time when a trigger is received without syncing timestamps may be to check the status of the metadata parameter RS2_FRAME_METADATA_GPIO_INPUT_DATA to detect whether a camera hardware sync pin is in a 'high' state (a trigger has been received) and then check the time if the pin is high.

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