You're going to attempt to stream 3 separate video and audio streams over a 512kbit link?

I think you need to look into more bandwidth, that's quite a low amount and I think you're going to see some issues from it.

It sounds like you've got a blank slate and aren't sure where to start doodling plans. Make sure you test the system thoroughly and keep cell phones for when the system bombs.

Maybe think a little smaller. Instead of full video conferencing, perhaps use text and audio, sort of like the old "You don't know Jack" site. Use an IM client as the method of 'buzzing in', post the questions on the screens as you read it, then allow the user to speak a reply. As a fallback, make sure people at each location have the questions and answers in case there's tech problems, and to verify the answers in case 'shenanagans' are called. If you have the spare bandwidth, then maybe you can snap a picture every 5 seconds and post it. Best not to overthink it, save those braincells for the questions, and the beer!

if you have buzzers that lock out other people when you buzz in your gonna have to deal with the latency times for it to lock the others out

I think this would make a quiz show, running on a 512k line, almost impossible. You'd never be able to tell who really buzzed in first- worse, every location would have a different "first" buzzer and there'd be no way to tell who was ACTUALLY first.. unless you did somethin wild like sync timecodes at the source and after every buzz use instant sync tape relay to figure out who REALLY buzzed in first...

Considering you're looking at doing this for charity, have you considered contacting the folks at NTN [ntn.com] who do this all the time and see if they'd be willing to set you up for a special occasion?

Just a thought...

You haven't explained the quiz-show setup. Where is the quizmaster? How are you asking questions and how are contestants answering? In a pinch: Use Yahoo Messenger for the video links and then create a Yahoo chatroom and turn on the voice-chat. Use VNC to control the remote machines; if you have three pubs, I would suggest getting another machine to handle the VNC'ing, and just leave all the others hooked up. Pub1 views Pub2 and Pub3, Pub2 views Pub1 and Pub3, Pub3 views Pub1 and Pub2 --- and they're all in the same voice-chat. Is it oh-so-hacker cool? No. Is it free and will it work? Yes.

Sync the clocks with NTP and have the first click win. A small delay while the machines poll each other wouldn't be out of order.

Considering you're running this as amateur, you better do it plain and safe. You're going to waste much more time/money into this than you can gather.
Maybe you should organize something more conventionnal, with the help of your municipality maybe ?

I'm not pessimistic, I'm realistic, it's about dying people, don't forget that point. Do it the efficient way.

Why not? It might be the best/easiest option available. Why must you automatically dismiss all things Microsoft?

This sounds like just another case of self-defeating zealotry.

My advice? Pick whatever works best meets your needs.

From the summary, it looks like this is going to be a one-time thing, a charity event with the proceeds going to tsunami relief. Rather than spend all this time and money trying to set up a technological way to do this, why not just get three quizmasters with three PA systems? You'd have less expenses, so more money would go to charity. I'm assuming you are getting volunteers to run the quizzes, so I didn't figure in costs for paying the extra people.
Another thing I worry about is, if you're only doing it once, you can count on stuff going wrong. Things always do with something this complicated. I could see if you were going to do it week after week, because after a few weeks you'd get the hang of it and you could streamline the process. But if you're just planning on doing a one-shot event, stick to the tried and true. You could rent three PA rigs for the evening and be good to go. Hope this helps.

Although you may not be a fan, keeping things simple and not re-inventing the wheel might help. You should consider contacting a company like WebEx which provides great application sharing/conferencing services to many companies, and explain what you're doing and why. It might be a great idea for them to participate (good publicity, maybe they'll have a press release) and get more attention for your event and ultimately raising money. If they donate their services you acknowledge them as a sponsor, etc.

remember that the uplink speed with ADSL will be less than the downlink speed. For the UK 256kbit/s upload is common.

IM!? To borrow a phrase from Halo PC, "lagggggg."

For validity of who buzzed/answered first, you'd have to a) have a system to offset for the latency between the locations or b) conduct the timing and answering separately, and mayhaps do a bonus or whatnot for whoever answered first.

I thought of that actually. They could have the audio spooled to the remote locations and have them recite the question at the same time, again thanks to NTP.

Mod this parent up... WAAAAY up...

As a Broadcast Engineer who has actually DONE something like this before, over a satellite link, let me give you some pointers...

The lag in your answer time is going to KILL you over the internet. I would HIGHLY suggest having someone at your "host" location on the phone to each of the other pubs, and keeping an ear on the host pub, and let them be the "final judge" on who rings in first. That way there is no question as to someone being "locked out" due to lag.

The on-the-fly answer that CoordinateZero gave you is the best one that I have seen from reading practically every response on this topic. The Yahoo chatroom is going to be kludgy, but it WILL work, and it is FREE.

A few years ago I was the Engineer in Charge of a 3-way bingo tournament from 3 different indian reservations. The top purse was $1 mil... I had to coordinate 3 camera crews, 3 satellite trucks, intercom and audio between all three locations, and provide a master feed of all 3 locations back to the parent casino. Trust me... You get some little old lady screaming bloody murder because she thinks she said "bingo" first, you will learn the TRUE meaning of "real-time" communications.

I recommend a slight change in overall scope:

Each location has it's own 'contest', with the computer providing a results display of each of the 3 seperate matches. Some form of bar chart could be kept 'live' showing the results for each pub.

You could 'film' 30-second interviews of the contestants, between questions, and play them back during "intermission" periods.

This way each of the pubs is competeing for an ultimate score, highest scoring pub/player = 1st place, etc.

This eliminates the majority of the concerns around latency, and provides a more effective use of the equipment at hand.

I played a lot of scholastic bowl in high school, and I'm gonna have to call shenanigans on your claim that l;ag won't be an issue. A tenth of a second can be a motherfucker. That said, it's soluble. In this context, it doesn't matter who rings first. It matters who rings with th least delay after seeing the question. So, my suggestion would be to have a small program that displays the question to the players, and starts a local timer as soon as the question is displayed. As soon as somebody rings in, you send a message back to the server with the amount of delay. Whoever was "first" is called on by the moderator, and given a chance to answer.

Fairly easy to do with a little Java app, or any language like that, and a little socket programming.

As for the video... Would Video Lan Client work for something like this? I've never tried to use it over the 'Net, but it works great on my home LAN, runs on almost anything, and will play from a live video source, and will do transcoding on the fly. What more could you ask for?