topic Re: Grabbing the latest D415 frame set in Items with no label

Grabbing the latest D415 frame set

LMuel — Wed, 23 May 2018 07:44:38 GMT

I am using the D415 in addition to different camera with a slow frame rate.

When I use the wait_for_frames() it returns a set of frames that seems to be

around 90-100ms older than expected. Is there a way to grab the latest

frame or wait for the next frame set to be recorded?

I am using python.

Re: Grabbing the latest D415 frame set

MartyG — Wed, 23 May 2018 07:51:38 GMT

The code below (which I assume is C++) waits for a coherent set of frames.

rs2::pipeline pipe;

pipe.start();

rs2::frameset frames = pipe.wait_for_frames();

rs2::frame frame = frames.first(RS2_STREAM_DEPTH);

if (frame)

frame.get_data(); // Pointer to depth pixels,

// invalidated when last copy of frame goes out of scope

Re: Grabbing the latest D415 frame set

LMuel — Wed, 23 May 2018 11:16:26 GMT

Hi Marty,

thank you. The code you provided seems to behave in the same way

frame = pipeline.wait_for_frames()

frame.get_depth_frame()

does. I still get the same offset.

I currently grab a single frame from a different camera (not an Intel product) and then

run the code you provided. The frame I get from my other camera lags behind the

D415 frame set by around 100ms. I would assume this to be impossible if the

code waits for a new set of frames?

Re: Grabbing the latest D415 frame set

MartyG — Wed, 23 May 2018 11:34:45 GMT

It sounds like your project would benefit from hardware sync, where the 400 Series camera can have its timestamp synced with a non-Intel sensor that is attached to the camera via a cable. The 400 Series cameras have something called GPIO pins that can be used for this. Intel wrote a white paper recently about creating a multi-camera setup.

The paper says: "Multiple cameras can be connected to a PC and will be able to stream independent data. The cameras operate in the "Default" mode and will stream asynchronously. However, if it is desired to hardware synchronize (e.g. HW sync) them so they capture at exactly the same time and rate, the cameras will need to be connected via sync cables, and will need to be configured in software to have a single master (or an externally generated sync signal) and multiple slaves. The connector port can be found on the cameras as shown below, and a cable will need to be assembled"

Here is the link to the white paper:

https://www.intel.com/content/dam/support/us/en/documents/emerging-technologies/intel-realsense-technology/RealSense_Multiple_Camera_WhitePaper.pdf https://www.intel.com/content/dam/support/us/en/documents/emerging-technologies/intel-realsense-technology/RealSense_Mul…

Intel are still working on adding hardware sync support, with a release estimate for this feature of around Q2 2018 (sometime between now and June 2018).