OpenMV M7 Cam Latency

General discussion about topics related to OpenMV.
jenga_jesse
Posts: 1
Joined: Sat Aug 18, 2018 12:28 pm

OpenMV M7 Cam Latency

Postby jenga_jesse » Sat Aug 18, 2018 12:48 pm

Hello,

I am part of a robotics team that tracks an orange ball. We are looking into using the OpenMV camera but our issue last year was oscillating when the robot was moving to the ball. Because of this, our deciding factor of whether to use the OpenMV M7 Cam would be to run a latency test, that is the time it takes from the moment the color appears in the camera's view to when it recognizes the color. I ran a latency test that lights an orange LED and starts a timer. When the color is recognized, it stops the timer. At 320x240 resolution with the frame buffer disabled, I measured a latency of around .015s. So that's the time it takes for the image sensor to capture and transmit the data plus the time it takes to run find_blobs() on one blob. I immediately stop the timer before doing anything else, like drawing a circle around the color. Does that seem about right?

Thanks!
User avatar
iabdalkader
Posts: 544
Joined: Sun May 24, 2015 3:53 pm

Re: OpenMV M7 Cam Latency

Postby iabdalkader » Sat Aug 18, 2018 8:06 pm

Hi,

Sounds about right, @QVGA you get 84FPS so a frame every ~12ms. Worst case scenario 12ms + time to detect the blob. If you can lower the exposure the max time will be less, ex. sensor.set_auto_exposure(False, exposure_us=4000) outputs about ~100FPS (10ms+ blob time should be 13ms total).
jenga_jesse wrote:
Sat Aug 18, 2018 12:48 pm
Hello,

I am part of a robotics team that tracks an orange ball. We are looking into using the OpenMV camera but our issue last year was oscillating when the robot was moving to the ball. Because of this, our deciding factor of whether to use the OpenMV M7 Cam would be to run a latency test, that is the time it takes from the moment the color appears in the camera's view to when it recognizes the color. I ran a latency test that lights an orange LED and starts a timer. When the color is recognized, it stops the timer. At 320x240 resolution with the frame buffer disabled, I measured a latency of around .015s. So that's the time it takes for the image sensor to capture and transmit the data plus the time it takes to run find_blobs() on one blob. I immediately stop the timer before doing anything else, like drawing a circle around the color. Does that seem about right?

Thanks!
Estabrook
Posts: 1
Joined: Mon Aug 27, 2018 6:05 am

Re: OpenMV M7 Cam Latency

Postby Estabrook » Mon Sep 03, 2018 7:14 am

I'm guessing it's not possible to lower the latency under 10ms in total?
User avatar
kwagyeman
Posts: 2286
Joined: Sun May 24, 2015 2:10 pm

Re: OpenMV M7 Cam Latency

Postby kwagyeman » Mon Sep 03, 2018 1:42 pm

Um, if you set the exposure to nothing you'll have no latency but you'll need very bright lights to see.
Nyamekye,

Return to “General Topics”

Who is online

Users browsing this forum: No registered users and 2 guests