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Question

Connecting many cameras (about 6) through one or three usb p

by anhnhamoi / May 19, 2015 12:10 AM PDT

I am planing to connect about 6 cameras through one or three usb 2.0 port.
Should I use an usb hub?
Lets say here are some info about images:
Size: 5200 x 3500
Depth of bit: 24 bits
Frame rate: 1 picture/second
All cameras are same.
Is there any problem with this?
Thank you.

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All Answers

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Answer
Good luck.
by R. Proffitt Forum moderator / May 19, 2015 12:13 AM PDT

Be sure you do this with a known setup. Very few USB cameras support more than one camera and then you need software to get it working. And yes you use a hub. But that's not the big hurdle.

What works better are IP network cameras.
Bob

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Data transfer rate
by anhnhamoi / May 19, 2015 1:27 AM PDT
In reply to: Good luck.

Thank you, R. Proffitt.

With that hub, does the data transfer rate decrease compared to one camera one USB?
For example:
With one camera-one USB port: data transfer time = 1s
Now with five cameras capturing image at the same time sending these images to USB port.
Does it also take 1s or 5s?

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It was not about the transfer rate.
by R. Proffitt Forum moderator / May 19, 2015 1:44 AM PDT
In reply to: Data transfer rate

It was all about support for many USB cameras, drivers and software. I did try this years ago and came away with a healthy appreciation that you must use a setup that someone has done before. If you run out and buy cameras you will 99.99% likely fail.

With IP cameras, it's designed from the outset to work with more than one camera.
Bob

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Can't use IP cameras
by anhnhamoi / May 19, 2015 1:52 AM PDT

Well, I must use Canon EOS camera and there is no other choice. If I use usb hub, will it be OK?
And how about transfer rate as above?

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I guess you didn't read the above.
by R. Proffitt Forum moderator / May 19, 2015 2:00 AM PDT
In reply to: Can't use IP cameras

It was not about transfer rate. And as you didn't reveal it was an EOS, I would not have warned you off again.

There is another way to make do with the EOS. But there are so many models in that line that I'll just share how I would tackle this.

1. Put EyeFi cards in each camera.
2. Rig up a remote control for each with RasBerry Pi's or such.
3. Write up the app in Visual C#.

http://www.breezesys.com/DSLRRemotePro/ should be contacted too.

I see some models have WiFi so that could make it happen.

I can't impress on you enough to abandon USB. It's not about bandwidth. It's the software, drivers and more. You never mentioned Windows, but you may not know that more than one USB camera in Windows is nothing but pain. Well, at least someone tried to save you. I wonder if you'll try anyway.
Bob

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a PC with 6 usb port
by anhnhamoi / May 19, 2015 2:17 AM PDT

Thanks for the idea!
I will study about this method.
How about if I find a PC with 6 usb port and I connect each camera with each usb?
Is it OK and how about data transfer rate?

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I fear you are not going to succeed.
by R. Proffitt Forum moderator / May 19, 2015 2:24 AM PDT
In reply to: a PC with 6 usb port

I shared but didn't get you to turn away from the brick wall.

OK, a little about me. Over the years I've done a lot of work in engineering of video surveillance gear. From cameras, DVRs, apps and more. Along the way we've done image work from people counters, license plate readers and more.

If you can't take a hint you are headed to a brick wall then please accelerate and crash so we can pick up the pieces sooner than later.

If you are in the SoCal area maybe we can meet and see if there is another way.
Bob

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a PC with 6 usb port
by anhnhamoi / May 19, 2015 2:42 AM PDT

Thank you for the help!
I appreciate your advice. However, this is a must to me. I have no choice.
I wish I lived there but I will try because I bought all these cameras.

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Then you must crash test this quickly.
by R. Proffitt Forum moderator / May 19, 2015 2:44 AM PDT
In reply to: a PC with 6 usb port

Having been down the more than one USB camera road a few times I had hopes to help you avoid the pain. But let's see if you repeat the experience.
Bob

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Again.
by R. Proffitt Forum moderator / May 19, 2015 2:47 AM PDT
In reply to: a PC with 6 usb port

I can't guess why some USB hub would do. These USB hubs are pretty much what's inside the PC. Since it's not bandwidth at 1 frame per second, I don't see why you persist in a PC with 6 ports.

Since you have the cameras and one working setup, try 2 cameras first. You'll find out fast if the usual brick wall shows up.
Bob

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USB hub
by anhnhamoi / May 19, 2015 3:36 AM PDT
In reply to: Again.

Yes, I will try with two cameras first. Actually, I don't get what you mean about bandwidth and some points about usb hub.

1. Does usb hub allow many cameras connect and transfer data simultaneously to a single usb port?
2. If so, there should be a limit for number of cameras connecting to one usb port, right?

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Sorry.
by R. Proffitt Forum moderator / May 19, 2015 3:39 AM PDT
In reply to: USB hub

But after this many posts I've answered the USB bandwidth many times.

2. While there are limits in USB in general the USB multiple camera issue is one for the books. Usually the drivers don't support more than one. Or the app doesn't.

Specifically, ALL USB ports limit to one device per physical port. That device can be a hub which gives us more ports for the entire PC.
Bob

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Answer
Let me give you an exit plan.
by R. Proffitt Forum moderator / May 19, 2015 1:53 AM PDT

Let's say you dismiss all the prior discussions and warnings. You bought the cameras and found out what a mess you created and no one will help you fix it. What to do now? Time to add the missing USB to network (IP) part.

Example: https://www.raspberrypi.org/documentation/usage/webcams/

Bingo. A smart USB camera.
Bob

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Answer
Back to transfer time.
by R. Proffitt Forum moderator / May 19, 2015 4:03 AM PDT

I guess you are concerned about port speed. 98% of the transfer time is usually if not always other than USB port speed.

USB 2.0 is accepted at 480 megabits a second. Even the common 18megapixel jpeg weighs in at around 6MB so that's at most a quarter second transfer time. All the rest of the time is software or other stuff. Some hub at full USB speed should handle 4 pictures a second or 4 cameras if the drivers and software support such a thing.

However this seems to be lost on you. I've seen so many more than one USB camera disasters over the years that I would never commit to the design you seem to be heading toward.

By the way, I also have used or helped engineers with National Instruments vision software as well as authored a few too many other vision/photo apps over the years. Not that it matters. You appear to be heading toward a brick way.

Be sure to have an exit plan.
Bob

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