Multiple webcams using the same driver

Multiple webcams using the same driver

[Vitor P.]

Hello, all. I'm new to this list, and I bring a question. I'm sorry if the
archives hold its answer; I swear I've tried every search I could think of
and still didn't find a definitive answer to my question.

I'm trying to build a sort of Street View car, for kicks, using cheap
webcams as the source for the images. I have gotten seven Microsoft LifeCam
VX-1000 from a friend, and proceeded to connect all of them to powered USB
hubs. They were recognized, and a couple of V4L applications were used to
test them individually; all went great.

But my use case, alas, requires them to fire simultaneously, or as close to
at the same time as possible. I couldn't: whenever I tried more than one
camera on the same bus, "libv4l2: error turning on stream: Input/output
error
libv4l2: error reading: Invalid argument
v4l2: read: Invalid argument" popped on my face. On two different buses,
fine.

Is it really not possible to use this camera (with "sonixj") in conjunction
with sister cameras of the same model?

Thanks in advance. I apologize for any mistakes and my unquestionable
ignorance.

-- 
Vitor Peres
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Re: Multiple webcams using the same driver

[Bruno Barberi Gnecco]

Hello,

	I only tested 2 Lifecams (model 045e:075d) simultaneously and it worked, but I think they 
were on different buses. But you won't be able to synchronize USB webcams -- it seems to 
be impossible, as there is no hardware support for triggers (it's either internal or not 
supported by the USB). Some firewire cameras support that, but for most purposes you can 
live without synchronization if your frame rate is 30fps or more.

	Now, my turn: have you been able to turn off the autogain and autoexposure of these cams? 
Mine are recognized as v4l1 and I can't find a way to do that.

	See you,

> Hello, all. I'm new to this list, and I bring a question. I'm sorry if the
> archives hold its answer; I swear I've tried every search I could think of
> and still didn't find a definitive answer to my question.
>
> I'm trying to build a sort of Street View car, for kicks, using cheap
> webcams as the source for the images. I have gotten seven Microsoft LifeCam
> VX-1000 from a friend, and proceeded to connect all of them to powered USB
> hubs. They were recognized, and a couple of V4L applications were used to
> test them individually; all went great.
>
> But my use case, alas, requires them to fire simultaneously, or as close to
> at the same time as possible. I couldn't: whenever I tried more than one
> camera on the same bus, "libv4l2: error turning on stream: Input/output
> error
> libv4l2: error reading: Invalid argument
> v4l2: read: Invalid argument" popped on my face. On two different buses,
> fine.
>
> Is it really not possible to use this camera (with "sonixj") in conjunction
> with sister cameras of the same model?
>
> Thanks in advance. I apologize for any mistakes and my unquestionable
> ignorance.
>


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