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swifteagle1

Wireless camera on 802.11

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Hey yall,

Pretty cool website you got here.

I have a question for you.

Have any of you considered using 802.11b to send your video signals?

This way you could view on a laptop or a handheld device.

If not what were the reasons and the issues?

I'm, looking into doing this for project.

any feedback would be appreciated

swifteagle1

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Issue... as long as there is no device made for this, you would have to put a computer in the plane with either a high quality webcam or an analog camera like those we have and an analog -> digital converter (like those USB devices). Even if industrial PCs can be small, it will still be much bigger than the gear we use now. The power consumption also is much higher.

There are a few stand-alone WLAN cameras, but they are relatively big, and intended to be fixed. I've never had the opportunity to test one.

Another problem is the bandwidth. With 11Mbps the video you could send would be much lower quality than analog video. And the 11Mbps is at short range only! if you are 100m away from the access point, the transfer rate can drop at 1-2Mbps.

At home I have a 802.11g, in the flat it runs at the specified 54Mbps (though the actual transfer rate is more at 25), and if I go 200m away with my laptop I already lose the connection. That's definitely not enough, given also that when the connection is lost you generally have to come close to the AP to get it up again.

Hope this helps...

Kilrah

Edited by Kilrah

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I think it could be done. Modern PocketPCs such as the Ipaq are powerful enough to encode mpeg4 video at a reasonable framerate (I've had 10-15fps out of an old arm9 ipaq, so an Xscale model with Intel's MMX extensions should fly), and light enough to mount in a model aircraft. Unfortunately, I'm not aware of any publically available video encoder that will run on them (although I'm sure such a thing must exist). My own encoder was written as part of a proprietary research project.

The limitations on 802.11b/g mentioned earlier in the thread are probably the bigger problem, but line of sight over 802.11 has been achieved over a distance of several miles. You'd only need 512kbps-1Mbps to get reasonable SD video out of mpeg4 with the right motion estimation algorithm. Since an 802.11 link will give you QoS information, you could even modify the target bitrate of the encoder in realtime as the available bandwidth fluctuates. Mpeg4 also has excellent error recovery and concealment options, so one could stream over UDP and avoid some buffering and retransmission issues. I wonder if Apple's QT streaming server will run on an ipaq? Possibly under linux...

Obviously, one could do better with an h.264 based solution (25fps SD in roughly 512kbps), but I think it would be a struggle to fit it on a pocketpc. Maybe the baseline codec, especially since there's no license fee to use it...

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I am not sure what's the original goal is. If it is to send high resolution video then

you can try to use this:

http://catalog.belkin.com/PureAV_detail.pr...oduct_Id=178096

It will encode video into MPEG and send it out through 5 Ghz link with 5 channel diversity receiver. The resolution is 500 lines - equal to DV Camcorders.

I have already strapped one on my heli and did a flight test. It looks good but the box is quite bulky.

If the idea is to use high resolution wireless cameras then the bandwidth (for high frame rate, high resolution) will be an issue.

This camera has build-in compressor:

http://www.linuxdevices.com/articles/AT2441343146.html

but it will require dedicated wirelless bridge - not a light package to carry.

I believe the range can be improved with amplifiers, but again the question of the bandwidth remains.

Edited by cyber-flyer

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Use the demarc 300mw card with ext antenna and a sony IP camera with card slot.

http://www.demarctech.com/products/reliawa...cmcia-card.html

Range is measured in miles and video is about 8 FPS on fixed installtions.

Camera has PTZ and around 8 I/O's if I remember correctly.

Sample here: http://64.35.128.194

I am set-up with local DEM and a local ISP to provide live video in the event of a natural disater around here, but using analog to the ground station and then converting it into an IP stream and sent to the web via 802.11.

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I had a look at the sample and although I dont see a reason to use this in place of my current setup as I only use the video to point the still camera it may be the first step in being able to send multi feed with one transmitter. I have looked into this before and found the project beyond me but this may be the way to go. For those that dont know I would like to send 2 video feeds from my plane at the same time so that the pilot and camera operator both have their own screens to see what they need. The 8fps sample has proved to me that if I could send alternate frames (12.5fps for PAL) then this would be good enough. I have 2 worreis with this way of doing it, the first is weight and the second is reliability. In case anyone is thinking use 2 transmitters then the main reason is I cant recieve 2 signals at the same time with the setup I have and I dont want to totally redesign it, also it would double the power required in the plane.

As cyber-flyer says what is your reason for looking at using 802.11 ?

Terry

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Yesterday I talked to someone doing professional video job. He told me he had used a wireless system which consists of a composite -> MPEG hardware encoder -> WiFi transmitter along with a DV camera to cover an event. The system is worth $4000, and is a real brick. He actually was very deceived, as most of the time the bandwitdth was too low and he ended up with a choice between reduced framerate or huge pixels. He just turned back to analog, with the related cost reduction.

But maybe the 300mW WLAN card could be a good idea to help preventing this. I also don't know the exact conditions he was working in.

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Anyone know if the high resolution imaging chips like used in digital cameras can be controlled by a high speed microcontroller and the video signal sent through an ordinary video transmitter (at normal bandwidth, but slower syncs) without digital processing, and an image be reassembled at a slow frame rate (like 8 fps) in a computer on the ground? Might be simpler and lighter than MPEG encoding.

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