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| 3 or 4 webcams on half-circle ? https://forum.ipisoft.com/viewtopic.php?f=6&t=2990 |
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| Author: | sdesseignes [ Mon Jun 07, 2010 11:06 pm ] |
| Post subject: | 3 or 4 webcams on half-circle ? |
Hi, I am wondering if it is better to use 4 cams even in half-circle or just 3. TY |
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| Author: | Greenlaw [ Fri Jun 11, 2010 12:57 pm ] |
| Post subject: | Re: 3 or 4 webcams on half-circle ? |
Three is pretty good--much better than two or one--but four gives you even more accuracy. The trade-off is that you're dealing with a lot more data, so it all comes down to whether you're computer(s) can handle the extra bandwidth (for both video capture and motion tracking.) I find that with my old duo core laptop, I can capture from four Logitech cameras at 320 x 240 for each camera reliably at 30fps. I now have four PSP3 cameras which should work even better for capture (I haven't tried them yet.) But after capturing, I have to track the data on a quad core workstation with a beefier graphics card because the laptop is not adequate to process all this data. |
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| Author: | sdesseignes [ Fri Jun 11, 2010 11:55 pm ] |
| Post subject: | Re: 3 or 4 webcams on half-circle ? |
TY for your so usefull answer Greenlaw. Indeed I have a laptop and a desktop and they are good but not outstanding. So I do not yet whether they will be able to deal with so much data... |
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| Author: | Michael Nikonov [ Thu Jun 17, 2010 12:06 pm ] |
| Post subject: | Re: 3 or 4 webcams on half-circle ? |
sdesseignes wrote: Indeed I have a laptop and a desktop and they are good but not outstanding. So I do not yet whether they will be able to deal with so much data... With Sony PS Eye cameras, a 2GHz Core2 Duo laptop should be able to capture 4 camera video at 640x480 at 25-30 FPS. For Sony PS Eye 4 cameras at 640x480 at 60 FPS we recommend a quad-core CPU. |
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| Author: | nbarratt [ Wed Jul 21, 2010 9:18 am ] |
| Post subject: | Re: 3 or 4 webcams on half-circle ? |
My older laptop (Athlon 64 3700+) doesn't seem to be able to record even 3 PS Eye cameras at 320x240 30FPS. (CPU is maxed at 100%) Is that expected, or is there a chance I'm doing something wrong? I'm going to try dragging my faster desktop machine out to the garage tonight. |
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| Author: | Greenlaw [ Thu Jul 22, 2010 8:23 am ] |
| Post subject: | Re: 3 or 4 webcams on half-circle ? |
I'm going to guess that your laptop actually has only one USB2 controller onboard. This was my situation: I ahve 6 ports on my laptop, but when I looked in device manager, it only shows 1 USB2 controller, so all four cameras were bottlenecked at that 1 controller. Even so, I was able to get 640 x 480 at 30fps, but just barely. If you have anything else connected, like an external USB drive, that splits your bandwidth again. (FYI, I'm capturing video to an external eSATA RAID drive using a separate eSATA controller.) Hope this helps. FWIW, some users are getting good results recording as low as 320 x 240 at 30fps. You may lose subtlety and small motions, but it should still track the general motion. These days I've switched to using my desktop instead and it's been more reliable for getting a faster frame rate. I'm not getting 60 fps yet, but I haven't tried the latest software update yet, which has a feature that should improve RAID performance. I'm also testing USB 3.0 (card and drive) in my next session, which will probably happen this weekend. Greenlaw |
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| Author: | nbarratt [ Thu Jul 22, 2010 8:54 am ] |
| Post subject: | Re: 3 or 4 webcams on half-circle ? |
Thanks Greenlaw. Switching to my desktop got me recording at 640x480x30fps. I had some problems with tracking fast motion at that frame rate, so I'm going to try 320x240x60fps this weekend. |
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| Author: | Greenlaw [ Thu Jul 22, 2010 10:10 am ] |
| Post subject: | Re: 3 or 4 webcams on half-circle ? |
Yeah, as you probably realized, the higher frame rate reduces motion blur, and for fast motions that's better. Here's a tip for 'cheaters': When I did the sword test I intentionally kept my movements slow because I was capturing at 30fps and I had the idea that I can retime and speed up the animation later in my 3D app. (And hopefully make the character look a lot more skillful than I am.) Looking at the motion now, I feel the performance looks just a little 'mechanical' because I was overly conscious of this, but next time I think I can makes this look smoother. :p You can't perform everything in slow motion of course, but for some things it might help. G. |
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| Author: | andrew [ Thu Jul 22, 2010 1:01 pm ] |
| Post subject: | Re: 3 or 4 webcams on half-circle ? |
nbarratt wrote: My older laptop (Athlon 64 3700+) doesn't seem to be able to record even 3 PS Eye cameras at 320x240 30FPS. (CPU is maxed at 100%) Is that expected, or is there a chance I'm doing something wrong? If bottleneck is CPU then try to turn off compression. Greenlaw wrote: I'm going to guess that your laptop actually has only one USB2 controller onboard. This was my situation: I ahve 6 ports on my laptop, but when I looked in device manager, it only shows 1 USB2 port, so all four cameras were bottlenecked at that 1 port. Even so, I was able to get 640 x 480 at 30fps, but just barely. As to 3 PS Eye cams with 320x240 at 30fps - it should work even with one USB 2.0 controller. What is the display of your problem? 1. High values of frame drops => Not enough USB 2.0 bandwidth (Greenlaw case) 2. "Compression buffer overflow" message => Turn off compression 3. "IO buffer overflow" message => Turn on compression or use faster storage |
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