How many Webcams can be captured simultaneously?

  • Hi,

    for a new project I need to capture 80 (!) Webcams simultaneously. Not a video, just one single picture of each Webcam at the same time.

    If I have enough (active) hubs to connect all those webcams to my Mac, can the mac handle that many cams? (Resolution ~10 MegaPixels)

    I know how to capture a Webcam via QuickTimeSDK, so that's no problem... but 80..?! Is that possible?
    Or would I need to split the cams over 3 or 4 Macs and synchronize them?

    Aya~_______________________________________________
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  • Isn't USB limited to 63 devices per controller?

    -Daniel

    On Apr 13, 2010, at 4:59 AM, Aya Koshigaya wrote:

    > Hi,
    >
    > for a new project I need to capture 80 (!) Webcams simultaneously. Not a video, just one single picture of each Webcam at the same time.
    >
    > If I have enough (active) hubs to connect all those webcams to my Mac, can the mac handle that many cams? (Resolution ~10 MegaPixels)
    >
    > I know how to capture a Webcam via QuickTimeSDK, so that's no problem... but 80..?! Is that possible?
    > Or would I need to split the cams over 3 or 4 Macs and synchronize them?
    >
    > Aya~_______________________________________________
    > MacOSX-dev mailing list
    > <MacOSX-dev...>
    > http://www.omnigroup.com/mailman/listinfo/macosx-dev
  • I believe it is 127 devices per controller, including hubs (7-bit address with one reserved address). Investigate the star topology in the USB 2 spec, which will make getting this many devices on one network a little difficult, but you might have more than one USB controller in the computer.

    I think bandwidth is divided among devices, so your capture rate for this many 10MP cameras may be slow?

    -Owen

    On Apr 13, 2010, at 1:53 PM, Daniel DeCovnick wrote:

    > Isn't USB limited to 63 devices per controller?
    >
    > -Daniel
    >
    > On Apr 13, 2010, at 4:59 AM, Aya Koshigaya wrote:
    >
    >> Hi,
    >>
    >> for a new project I need to capture 80 (!) Webcams simultaneously. Not a video, just one single picture of each Webcam at the same time.
    >>
    >> If I have enough (active) hubs to connect all those webcams to my Mac, can the mac handle that many cams? (Resolution ~10 MegaPixels)
    >>
    >> I know how to capture a Webcam via QuickTimeSDK, so that's no problem... but 80..?! Is that possible?
    >> Or would I need to split the cams over 3 or 4 Macs and synchronize them?
    >>
    >> Aya~_______________________________________________
    >> MacOSX-dev mailing list
    >> <MacOSX-dev...>
    >> http://www.omnigroup.com/mailman/listinfo/macosx-dev
    >
    > _______________________________________________
    > MacOSX-dev mailing list
    > <MacOSX-dev...>
    > http://www.omnigroup.com/mailman/listinfo/macosx-dev
  • I don't know about the limits imposed by the OS, but I'm curious how you are planning to distribute these cameras. Are these all at a single location looking in different directions? Or are these scattered throughout an area?

    USB has a pretty limited maximum distance that you can run the cables. That may be more of a limitation than just how many your OS can handle.

    USB 2.0 can have cables up to 5 meters. There is also a maximum of 5 hubs in series. That gives you a theoretical maximum run length of 30 meters from the computer. You would need optical or CAT5 extenders if you wanted to go longer than that.

    -Chris
  • 6 bits, 7 bits, what's one bit between friends?  :p
    On Apr 13, 2010, at 11:59 AM, Owen Imholte wrote:

    > I believe it is 127 devices per controller, including hubs (7-bit address with one reserved address). Investigate the star topology in the USB 2 spec, which will make getting this many devices on one network a little difficult, but you might have more than one USB controller in the computer.
    >
    > I think bandwidth is divided among devices, so your capture rate for this many 10MP cameras may be slow?
    >

    Yes, it is, but I think he was saying that it's 10 MP total, not per camera. There will be a fair amount of overhead just from bus mastering at that number of devices though.

    -Daniel
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