[Nottingham] Webcam snapshots

[Martin]

On 25 August 2011 05:18, James Moore <jmthelostpacket at googlemail.com> wrote:
[---]
>>
>> Anyone any ideas? I think this has got to be one of those things that
>> has already been done...
>>
> IME Zoneminder grabs frames on a round-robin basis, which has the added
> bonus of complete system failure if one of the cameras fail(!) since it
> would just sit there and wait until the camera comes back online. Probably
> not the best thing to use if you're using remote cameras over the internet.
> So basically what you would have on a four camera setup is every fourth
> frame is grabbed from each camera, in sequence, or a net of 7fps per camera.
> Good if you're doing bullet time, not so good if you're doing what I think
> you're trying to do - simultaneous grabbing from all four units?

Good thoughts there. Bullet time with just four webcams... Mmmmm,
tempting but I'd better not get distracted with effects! :-)

However, the source problem is that such as Zoneminder require all the
webcams to be continuously streaming video. It then just selects one
of the frames every so often and ignores/discards the rest. Each
webcam requires the full bandwidth of USB2 all for itself, and so you
can't run more than one webcam because the USB2 hub root gets
choked...


Hence, is there any way to use the four webcams in reasonable time (1
snapshot per second or two) without them all continuously streaming
data over the USB2?

I'm using an atom uATX board and I've already used the one PCI slot :-(


Cheers,
Martin