We're trying to make a motion capture system, and is looking into the possibility of using web cameras. We're going to use at least 3 cameras, and we need them to be synchronized. That is we need them to take pictures at the same time.
I'm thinking that this could be done by trigging all the cameras to take a still image at the same time. For this to work there need to be a known and constant delay in the cameras. It would then be possible to calibrate, say camera 1 takes 20 ms to fire, camera 2 25ms an so on. My question is could we assume constant delay? (I'we been trying to make an application to measure still image delay and possible frequency but I'm getting an unwanted popup from Windows that stops my program, because I must push a button to get further :-().
I'm also wondering about using video streams. One could possibly get about 15-30 pictures per second. Would it be some way to get synchronization with video? Is the frequensy constant (if the bus could take away all the pictures) or is there some kind of information in the stream (or by asking the camera) that could be used to help synchronization?
We're trying to make a motion capture system, and is looking into the possibility of using web cameras. We're going to use at least 3 cameras, and we need them to be synchronized. That is we need them to take pictures at the same time.
I'm thinking that this could be done by trigging all the cameras to take a still image at the same time. For this to work there need to be a known and constant delay in the cameras. It would then be possible to calibrate, say camera 1 takes 20 ms to fire, camera 2 25ms an so on. My question is could we assume constant delay? (I'we been trying to make an application to measure still image delay and possible frequency but I'm getting an unwanted popup from Windows that stops my program, because I must push a button to get further :-().
I'm also wondering about using video streams. One could possibly get about 15-30 pictures per second. Would it be some way to get synchronization with video? Is the frequensy constant (if the bus could take away all the pictures) or is there some kind of information in the stream (or by asking the camera) that could be used to help synchronization?
Hmmm...interesting problem. So, just to clarify, are you talking Motion Capture or Motion Detection? I ask because I've not heard of Motion Capture that isn't video related - not to say it isn't done, just not come across it. And does a webcam give you enough resolution and image clarity?
Nonetheless you need a clock that is synchronized across the webcams. How accurate do you need it - 30fps would give you granularity of 33ms? The problem with a "one time" calibration is that hypothetically the latency could change, though I would suspect the variance would be minimal.
Given all the caveats \ questions you could just point the cameras at a single stop watchs, take a snapshot or video and look at each cameras latency that way.
Hmmm...interesting problem. So, just to clarify, are you talking Motion Capture or Motion Detection? I ask because I've not heard of Motion Capture that isn't video related - not to say it isn't done, just not come across it. And does a webcam give you enough resolution and image clarity?
Nonetheless you need a clock that is synchronized across the webcams. How accurate do you need it - 30fps would give you granularity of 33ms? The problem with a "one time" calibration is that hypothetically the latency could change, though I would suspect the variance would be minimal.
Given all the caveats \ questions you could just point the cameras at a single stop watchs, take a snapshot or video and look at each cameras latency that way.
We're talking Image Capture (this is done today by Marlin cameras - which has a synchronization mechanism ). As for the resolution it should be ok. We're not sure about the image quality though.
As you say synchronization is depending on the frequency.
We've already thought about stop watch (or screen watch ;-). Just wanted to know if anybody with more knowledge of the cameras have ideas that could be helpful.