4 Interleaved V120 cameras - setup

rschoele · Post by **rschoele** » Wed May 12, 2010 12:38 pm

Hello,

I'm taking over direction of a project that one of our former software engineers was working on. I need to get up to speed so after I post my question, if there is already a thread covering my question, please direct me there.

To cut to the chase I'll tell you what I'd like to do and you can tell me if I'm crazy :crazy: or the actual direction I need to go in!

Our system needs to track laser spots on a screen, spots are NIR and approximately 1" in diameter at 15feet. Spots occur at very high rates with multiple spots to a video frame. Tracking is in 2D only.

I want to use 4 V120 cameras interleaved for a complete frame rate of 480Hz. All 4 will be daisy chained with the sync cable, all 4 will connect to a USB hub with a single USB connection back to the host.

We really don't want to run any third party software on our system, so my intent is for a custom application and your camera API.

So from a HW view - I think what I listed above is feasible - agree?

From SW view - can I achieve what I want to do using your optitrack SDK?

Thanks for your time.
Ryan Schoelerman
Electronics Engineer
Advanced Interactive Systems

rschoele · Post by **rschoele** » Wed May 12, 2010 1:08 pm

well searching I believe I've answered some of my questions, please confirm though.

V120 cameras use the external camera-to-camera sync cable only, no optihub- which is fine

I cannot use the optitrack SDK to interleave the cameras for a 480Hz frame rate?

I have to use the tracking tools to achieve the interleaved frame rate?

Birch · Post by **Birch** » Wed May 12, 2010 1:45 pm

[quote=Ryan_Schoelerman]well searching I believe I've answered some of my questions, please confirm though.

V120 cameras use the external camera-to-camera sync cable only, no optihub- which is fine

I cannot use the optitrack SDK to interleave the cameras for a 480Hz frame rate?

I have to use the tracking tools to achieve the interleaved frame rate? [/quote]

Correct for all of the above with two qualifications :

* Each V120:SLIM camera would require a sync breakout cable to expose the sync jack

* Adjusting the shutter offset is not currently available via the Tracking Tools API. It is possible to set the offset in the Tracking Tools UI application and save that out as a project which can then be loaded using the API.

We'd like to support your use of the cameras, so please contact our support group via email (support@naturalpoint.com), include a reference to this thread and we'll see what might be possible.

rschoele · Post by **rschoele** » Wed May 12, 2010 2:23 pm

Please reference the same topic in the OptiTrack General Forum
4 Interleaved V120 Cameras

[quote=NaturalPoint - Birch Zimmer][quote=Ryan_Schoelerman]well searching I believe I've answered some of my questions, please confirm though.

V120 cameras use the external camera-to-camera sync cable only, no optihub- which is fine

I cannot use the optitrack SDK to interleave the cameras for a 480Hz frame rate?

I have to use the tracking tools to achieve the interleaved frame rate? [/quote]

Correct for all of the above with two qualifications :

* Each V120:SLIM camera would require a sync breakout cable to expose the sync jack

* Adjusting the shutter offset is not currently available via the Tracking Tools API.

[/quote]

Yes, I know of the breakout cables and have those. By 'shutter offset' is this what your refering to for interleaving video frames? i.e. getting a 480Hz frame rate?

I take this to mean 4 synced 120Hz cameras all operate at 120Hz and all their shutters open at the same time. - yes?

So then the next question would be what can I do or what are some options?

rschoele · Post by **rschoele** » Wed May 12, 2010 2:32 pm

Is there source code or any addition to the OptiTrack API that could support adjusting the shutter timing for synced V120 cameras?

Birch · Post by **Birch** » Wed May 12, 2010 3:24 pm

As mentioned above, there is not currently support for adjusting the shutter offset using the OptiTrack SDK - we encourage you to contact us via email to see what might be possible.

[quote=Ryan_Schoelerman]By 'shutter offset' is this what your refering to for interleaving video frames? i.e. getting a 480Hz frame rate?

I take this to mean 4 synced 120Hz cameras all operate at 120Hz and all their shutters open at the same time. - yes?

So then the next question would be what can I do or what are some options? [/quote]

Yes, the shutter offset/delay is used to interleave capture timing of frames from multiple cameras. Their shutters do not open at the same time and each individual camera still operates at 120hz. If you want to achieve 480hz with 4 x V120:SLIM cameras the exposure for each camera would be staggered by 1/4 of the frame time from the other cameras.

To do that the following shutter offsets would be used :

camera 1 : 0 msec (0/4th frame offset)
camera 2 : 2.083 msec (1/4th frame offset)
camera 3 : 4.166 msec (2/4th frame offset)
camera 4 : 6.249 msec (3/4th frame offset)

Notes :
1000msec / 120hz = 8.3msec per frame
8.3msec / 4 cameras = 2.083msec

rschoele · Post by **rschoele** » Wed May 12, 2010 3:55 pm

sorry, I read the one post too quickly and took it to mean post the thread in the support section instead of general. I will be emailing you now.

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