Wireless video streaming - Page 1
Forum section: electronics / projects

author: cyberfish
author_rank: Regular Contributor
timestamp: October 01, 2010, 03:49:30 am
content: I'm working on an RC quadrocopter and need some way to stream video.I've been doing a lot of research, and it seems like the only way to get the bandwidth (~1Mbits/s) I need is to use wifi.Is there any other option? I'm trying to avoid wifi because it adds a lot of complexity, and therefore a lot of things to potentially go wrong.I need to stream an at least 640x480 video feed at >10fps. It will be compressed MJPEG. As for range, I'm aiming for 1km, but that's quite optimistic.My onboard computer is a Gumstix, so I'm not too worried about interfacing (it has SPI, UART, I2C).Suggestions?Thanks

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: October 01, 2010, 03:54:04 am
content: Suggestion? Yea. Transmit analog video. Framegrab it on the ground if you ultimately need it digital.

author: cyberfish
author_rank: Regular Contributor
timestamp: October 01, 2010, 03:57:41 am
content: That sounds like a good idea. I have never done any analog video, though, and don't really know how they work.I Googled them up a bit and they all seem to be huge (my chopper is about 500g-1kg), for security monitoring, with short range. I was probably looking at the wrong places.Can you suggest something concrete so I can get started?

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: October 01, 2010, 04:16:21 am
content: Well, I think I'd start with something like this ...http://www.geeks.com/details.asp?invtid=MINI-WIRELESS-CAM&cat=VIDIt says the range is 150 feet, but I'd replace both antennas. Get a Yag or cantenna or something for the receiver and have a friend in charge of keeping it pointed at the copter. Might even be able to add an amp before the receiver.You could probably do better than the little wire whip on the transmitter as well.Anyone know if the antenna on a wifi router has any gain?

author: cyberfish
author_rank: Regular Contributor
timestamp: October 01, 2010, 04:46:58 am
content: That looks good, but the range is way too short, even with high gain antenna. Even with an antenna with 6dB higher gain, that's just 300 feet.6 dBi wifi antennas are pretty common. >10 dBi directional antennas are also available.

author: sonicj
author_rank: Frequent Contributor
timestamp: October 01, 2010, 07:08:00 am
content: is this a 450? is AUW 500g or 1kg? big difference!and most importantly, what is your budget?-sj

author: sonicj
author_rank: Frequent Contributor
timestamp: October 01, 2010, 07:24:36 am
content: ohh yea... what is your control frequency? what country are you located?

author: Simon
author_rank: Unknown
timestamp: October 01, 2010, 12:46:38 pm
content: would a lower frequency get you more range ? there is the 900 MHz version:http://www.geeks.com/details.asp?InvtId=MINIWL-CAM-900-PB&cpc=RESXbut they don't state the range

author: cyberfish
author_rank: Regular Contributor
timestamp: October 01, 2010, 04:26:12 pm
content: Weight is not set yet, since I'm still in design phase.Budget is hard to say. If we use digital, I have a USB webcam already (that I have successfully interfaced to my Gumstix), so we just need the radio. For wifi I even have the radio already (Gumstix built-in).But I'm willing to experiment with analog video options in <$50 range.QuoteI was planning to use the same radio for control and streaming, which may or may not be a good idea (link saturation, latency, etc).QuoteAll else being equal, I believe lower frequency means slightly longer range. But there are many other factors, so it's impossible to tell.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: October 01, 2010, 04:55:40 pm
content: Back up a second ... are you sure you can get 1 Km range out of your remote control system?

author: sonicj
author_rank: Frequent Contributor
timestamp: October 01, 2010, 05:50:42 pm
content: problem with wifi is latency and reliability. analog is the way to go.<$50 wont get you very far. i would recommend 500mw @ 900mhz or 1.3ghz and 1w @2.4 ghz. 1/2 wave inverted vee on the VTX, diversity patches (or similar gain) on the VRX. min 480 lines camera.450 size heli at minimum. 500 or larger is easier to fpv.expect problems! a rc helicopter is a very unforgiving environment for this sort of thing. deep pockets, patience and a lot of time are all required.-sj

author: cyberfish
author_rank: Regular Contributor
timestamp: October 01, 2010, 08:19:33 pm
content: QuoteYeap. If I use analog video I will probably use xbee pro's for control. They can do 2 miles.QuoteWell, so far I've not seen any small analog camera/transmitter with significant longer range than wifi. Using wifi also has the advantage that I can potentially make a remote control with a phone or something.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: October 01, 2010, 08:24:07 pm
content: Well, they have this one ...http://www.geeks.com/details.asp?invtid=AICN777W&cat=VIDThe pan/tilt would be cool, but you could probably strip the thing down to the essential video function and cut a LOT of the weight.

author: sonicj
author_rank: Frequent Contributor
timestamp: October 02, 2010, 12:48:21 am
content: heres one.http://www.bevrc.com/bev-900m-800mw-p-55.htmlwith the proper antennas, this will get you well beyond 1km. you still didn't mention what country. this requires a license pretty much worldwide. some countries, 900mhz may not be an option.-sj

author: sonicj
author_rank: Frequent Contributor
timestamp: October 02, 2010, 01:25:31 am
content: i would have sworn you said helicopter.... quads are MUCH easier!Quote from: JohnS_AZ on October 01, 2010, 08:24:07 pmpan is not needed in a quadcopter.-sj

author: cyberfish
author_rank: Regular Contributor
timestamp: October 02, 2010, 02:34:14 am
content: Sorry I'm in Canada. I don't think I want to get a license though. Too much trouble just for the range, and it's kind of nice to just have one radio.And yes it's a quad. I thought helicopter is the general term for all rotary wing aircrafts.

author: sonicj
author_rank: Frequent Contributor
timestamp: October 03, 2010, 11:47:08 am
content: Quote from: cyberfish on October 02, 2010, 02:34:14 amyou are right, helicopter is a generic term. generally with those who closely follow rc, helicopter would lead one to think ccpm. (FP being fixed pitch, tricopter = 3, quadcopter, gyrocopter, etc... )i do not know a of a single radio systems that will meet your needs.http://www.rcgroups.com/forums/showthread.php?t=1147430<== comprehensive discussion led by one the best rf guys in the fpv scene.-sj

author: cyberfish
author_rank: Regular Contributor
timestamp: October 04, 2010, 05:05:11 pm
content: QuoteThanks for the link!That looks very awesome. Very fun read.And I think I found something that MAY work (if it works as advertised). 500mW bi-directional amplifier.http://www.radiolabs.com/products/wireless/wireless-range-extender.phpOf course, the limiting factor here will be receive, since the transmitter on the chopper is pretty weak (15dBm).It says the Rx gain is 20dB, but does that really help? I thought the limiting factor would be SNR.Anyone care to shed some light?Thanks

author: andersendr
author_rank: Regular Contributor
timestamp: November 19, 2010, 05:43:43 am
content: Why not go all out and get ham radio license. Then you can operate a lot more power on a wide range of frequencies. 900MHz band is an option at around 250W I think for in Canada with the basic license. For your control you can even find 900MHz cellphone amps that are being pulled from service for pennies on the watt to make sure you never loose control, although video might be lost. Here is a link to the Radio Amateurs of Canada site,http://www.rac.ca/en/