Live Video Feeds

[ChazzQuire]

Hello,

 

I am helping run a gig night at school and want to set up a live video feed using, 2/3 cameras, with two sreens.

 

What do I need to do this? Can I control it from a pc or laptop- and if so what video cards do I need and what software will allow me to cross fade between the cameras- and put up graphics, notices etc

 

I am looking to do this the cheapest way possible.

 

Thank You

[theatre_bod]

It should be relatively easy to set-up, unfortunately I'm a mac user myself so I'm not sure about the best software for pc, trying searching the web - I found some great free trials and there's even free basic software out there too. On the other hand you could see if you could hire a small editing desk, I used to do it that way a few years ago, fairly simple to set several inputs and outputs. We used this recently for a theatre show and it worked fine. It's also a great way to go if you're wanting any of the kids to have a go since once it's set-up very little can really go wrong. Your best option really depends on what cameras you're using and the connections they come with. Well, hope this helps in some way,

Lou

[Nick S]

You'd probably be better off hiring a small vision mixer - I once worked on a show with similar demands to what you seem to need, and we hired out a small Sony vision mixer, which we used to switch between several sources (two cameras and a PC outputting a presentation). I certainly think it would save you a lot of time versus trying to do the same with a PC.

 

Although I've never used a PC for vision mixing, I'd expect it would place large demands on the video card(s) and processor, since you'd not only be generating titles live, but also inputting and outputting multiple sources. I'm sure someone with better knowledge will be able to correct me, though :)

[Ilthigore]

On a similar line, would it work to "vision mix" using a few RCA sockets soldered to a rotary switch or something. Obviously, you would only be able to go in a particular order, but would it work providing the switch was made quickly? I am a real scrimp-and-save person.

[david.elsbury]

No. A real vision mixer takes the incoming video signal, strips off the sync pulses from them all and gives them all new and the same sync pulses. So you do not get the image rolling or whatever when you change. Your homemade one will not work well because whenvever you change source, the image will probably roll all over the place. If going to a projector, it may be even worse, waiting for the projector to pickup the sync of the new signal - the screen may go blue or a message may appear. Not a smooth transition.

 

Do a friggin search- top right hand side of every page on the Blue Room. This has been covered before!!

 

Edit: Please don't listen to me... I was wrong. See below.

[JCoster]

Mmm... As lxdeptnz said, this HAS been covered before- by me :).

 

http://www.blue-room.org.uk/index.php?showtopic=5369

[ChazzQuire]

Thank You, next time ill search first, this is my first post, sorry :)

[Englishpete]

No. A real vision mixer takes the incoming video signal, strips off the sync pulses from them all and gives them all new and the same sync pulses. So you do not get the image rolling or whatever when you change.

<{POST_SNAPBACK}>

 

Why does my MX-70 roll when I do an instant change??

Pete

[James]

No. A real vision mixer takes the incoming video signal, strips off the sync pulses from them all and gives them all new and the same sync pulses. So you do not get the image rolling or whatever when you change.

<{POST_SNAPBACK}>

 

Why does my MX-70 roll when I do an instant change??

Pete

<{POST_SNAPBACK}>

 

Because a Vision Mixer does not do what david said I'm afraid

 

An analouge vision mixer relies on the video feeds being perfectly in time with each other when they hit the vision mixer.

 

I know this is being pedantic and anal but please bear with me

 

In a professionally set up situation the timing of video sources is controlled by using devices called time base correctors

 

some cheep and simple vision mixers have time base correctors built into them.

 

A simple vision mixer will have say 4 inputs on two banks and some way of switching or fading between them.

 

This may only have two TBCs

 

One for bank A and one for bank B.

 

Cutting or wiping from bank A to bank B is done via the TBC so appears to be smooth and clean,

 

If you cut on the active bus then you are not going via the TBC so the picture jumps.

 

Clear as mud?

 

Other suituations differ, not all vision mixers work the same

 

but saying that a vision mixer re times vision signals is like saying that a lighting desk is blue.

 

For homework try to research the frequency of the burst in a PAL signal,

Using that, Calculate using the speed of electricity through copper what the difference in time taken and therefore the phase difference that would occour from changing the length of a video cable by;

A) 1cm

B) 1'

c) 1m

 

James

[Englishpete]

For homework try to research the frequency of the burst in a PAL signal,

Using that, Calculate using the speed of electricity through copper what the difference in time taken and therefore the phase difference that would occour from changing the length of a video cable by;

A) 1cm

B) 1'

c) 1m

 

James

<{POST_SNAPBACK}>

HE he, thanks James. Ive used coax, ive used CCZ and CCU with external genlock, and switch-roll... damn it.

 

Mebe its the damn MX70, the MX50 dont roll like that does, ive used 3 MX70s now and same thing.

 

I wish I could afford myown kit then id know what was going on...

 

Pete