# Switching between computer and live feed



## anshu (Jan 11, 2012)

Hi All,
I'm working on our first show that is making "major" use of video projections. I have a pretty good handle on how everything works and a hookup but would love some input and advice.

The output is going to 2 older Eiki projectors on to two screens. I can send signal to them either with VGA or BNC.

The input is multiple sources. One is a live feed coming from an offstage location with a standard household camera, it has a RCA output and maybe a DV output. The second is coming from Qlab a series of precorded video clips. The computer will have a doublehead/triplehead attached to be able to provide separate output to either projector.

My question comes mostly from the switching. I am not familiar with how well Qlab handles video in video out? But if it worked well I could avoid having some sort of physical switcher. If I needed some sort of physical switcher what kind of signal would I send to the projectors and how would I convert either the computer or the camera into a compatible signal.

thanks in advance
Anshu


----------



## joeyfergie (Jan 11, 2012)

I am working on a show right now that has something similar (but more complex) than this. In our production, we have 6 independently controlled 40inch TVs, 3 Live Cameras, as well as a bunch of video and image content. This is what we have:

All 6 TVs are connected via VGA to a Mac Pro. We have the graphics card upgrade, which gives us a total of 6 displays. The TVs are 1080p, but we are only using a resolution of 720p (less pixels needed to be generated by the graphics cards). We also have a USB Video card for the operator's monitor (costs about $50). Our 3 cameras are SD (realized unless you're sitting in the first row, you don't notice it is SD. We are taking the AV Out (composite), and running that through a standard RCA cable (If possible, I would go BNC, but that is too much money for us) into a Composite to Firewire Converter box. This converts the signal to Firewire, which is then readable by QLab using the Camera Cue. We have a second firewire card as well, as the onboard card did not handle 3 cameras well. All the camera and video cues are then put in the Qlab as normal, and everything is controlled through that. This way our Mac Pro, via Qlab is the one actually controlling all of the screens. Our show doesn't open for another 2 weeks, but we are running Q2Q's now, and so far no problems!

Based on what you are looking at it seems this kind of solution will work for you. Although we are running off a Mac Pro, I have done video in Qlab (sans cameras) with just a Macbook Pro. I would try avoiding needing a switcher if possible. They are extremely expensive (you will be looking at at least $10K to buy a low end model). Being a Broadcasting student, these are also equipment that take a while to learn to use and use well.

Hope this helps!


----------



## museav (Jan 11, 2012)

joeyfergie said:


> I would try avoiding needing a switcher if possible. They are extremely expensive (you will be looking at at least $10K to buy a low end model). Being a Broadcasting student, these are also equipment that take a while to learn to use and use well.


I think you are referring to production style switchers, which may be beyond what is required in this case.

Anshu, you mentioned that "The computer will have a doublehead/triplehead attached to be able to provide separate output to either projector." The DHTG/THTG doesn't actually provide a separate output for each projector as much as make the two projectors appear as one, wider display. So instead of something like two 1024x768 projectors the computer would see the projectors as a single 2028x768 display with half of that on each projector.

QLab will work with FireWire cameras, although you might have to look at how far the camera is from the computer since a direct FireWire run without repeaters or conversion is limited to 15'.

Another consideration with live video is if it is really live. Others have more direct experience with this and can hopefully add their input, but the video out of a DV camera run into a computer running QLab, out of that computer to a DHTG and then into an LCD or DLP projector could result in noticeable latency or where the projected image visibly lags the live action. I don't know if that would be acceptable in your application or not.


----------



## joeyfergie (Jan 11, 2012)

museav said:


> I think you are referring to production style switchers, which may be beyond what is required in this case.



I was referring to a production switcher. Being a broadcast student when someone says 'switcher' that is the first thing I think of. There are other types of switchers (which I have used as well), which may work. A downside is if you want the camera to be able to go on both displays (then a video amplifier will be needed as well)


museav said:


> Another consideration with live video is if it is really live. Others have more direct experience with this and can hopefully add their input, but the video out of a DV camera run into a computer running QLab, out of that computer to a DHTG and then into an LCD or DLP projector could result in noticeable latency or where the projected image visibly lags the live action. I don't know if that would be acceptable in your application or not.



I have always noticed (a bit) of latency doing "live" cameras. With our current setup, the longest camera run we have is 100 feet. Going into Qlab then back to a TV (a 50 foot run of VGA), the delay is less than 1 second. Not really noticeable, unless you have someone clapping, etc (then you will have a AV sync issue, cuz the video will be behind the live audio). I have also done live video including a wireless camera, this time going to a projector. The sync time was about the same (closer to 1sec for the wireless camera).

All the times that I have done it, it is a case where only techies would notice a delay.


----------



## anshu (Jan 11, 2012)

joeyfergie said:


> I am working on a show right now that has something similar (but more complex) than this. In our production, we have 6 independently controlled 40inch TVs, 3 Live Cameras, as well as a bunch of video and image content. This is what we have:
> 
> All 6 TVs are connected via VGA to a Mac Pro. We have the graphics card upgrade, which gives us a total of 6 displays. The TVs are 1080p, but we are only using a resolution of 720p (less pixels needed to be generated by the graphics cards). We also have a USB Video card for the operator's monitor (costs about $50). Our 3 cameras are SD (realized unless you're sitting in the first row, you don't notice it is SD. We are taking the AV Out (composite), and running that through a standard RCA cable (If possible, I would go BNC, but that is too much money for us) into a Composite to Firewire Converter box. This converts the signal to Firewire, which is then readable by QLab using the Camera Cue. We have a second firewire card as well, as the onboard card did not handle 3 cameras well. All the camera and video cues are then put in the Qlab as normal, and everything is controlled through that. This way our Mac Pro, via Qlab is the one actually controlling all of the screens. Our show doesn't open for another 2 weeks, but we are running Q2Q's now, and so far no problems!
> 
> ...



Thanks for the reply! Sounds like this might work out for me. What kind of capture card are you using?


Fortunately in our situation, the input video is offstage so the lag should not be noticeable. I think my plan is going to be getting the video camera output in RCA and then using a capture card at the computer side, to avoid the long run of firewire.


----------



## Lambda (Jan 11, 2012)

museav said:


> QLab will work with FireWire cameras, although you might have to look at how far the camera is from the computer since a direct FireWire run without repeaters or conversion is limited to 15'.


You could use the camera's composite video out and send that signal over coaxial cable, using a video amplifier if the signal is too weak after the long run. Send that through a composite-firewire converter and then into Qlab. Then you can do all your switching in Qlab without any need for external switching devices. The cable won't add to the latency at all, but the firewire converter might.


----------



## joeyfergie (Jan 11, 2012)

We used this Firewire capture card: Newegg.ca - Canopus / Grass Valley High-quality Analog-to-Digital Video Conversion ADVC55 IEEE 1394 Interface. Check the US store, they may have them in stock (and I see you're from the US). Seems like they went out of stock in the Canada store just after I bought 3 of them. 

Composite out from the camera to a firewire converter box is you best bet. Straight firewire you will need a repeater about every 10 feet. These converters have audio input as well, if you need that. You will need to connect your sound system then to the Video computer, but that usually isn't too hard.


----------



## anshu (Jan 11, 2012)

joeyfergie said:


> We used this Firewire capture card: Newegg.ca - Canopus / Grass Valley High-quality Analog-to-Digital Video Conversion ADVC55 IEEE 1394 Interface. Check the US store, they may have them in stock (and I see you're from the US). Seems like they went out of stock in the Canada store just after I bought 3 of them.
> 
> Composite out from the camera to a firewire converter box is you best bet. Straight firewire you will need a repeater about every 10 feet. These converters have audio input as well, if you need that. You will need to connect your sound system then to the Video computer, but that usually isn't too hard.



Cool. Looks like Amazon has them. How long of a run are you going without a video amp?

Also need to figure out how many devices can run off bus power on firewire.

thanks for all you help everyone!


----------



## joeyfergie (Jan 11, 2012)

The longest we are going is around 100 feet, and the video quality is fine. We have 2 off the built in bus on our Mac Pro, and 1 on an additional card. You can buy power supplies for these, if you are concerned about power. I would be more concerned about having the video freeze/skip frames if you have too much data on one bus. What other devices do you have being used?


----------



## anshu (Jan 11, 2012)

joeyfergie said:


> The longest we are going is around 100 feet, and the video quality is fine. We have 2 off the built in bus on our Mac Pro, and 1 on an additional card. You can buy power supplies for these, if you are concerned about power. I would be more concerned about having the video freeze/skip frames if you have too much data on one bus. What other devices do you have being used?


 

Indeed. Well the iMac only has the one firewire bus unfortunately. I am running a Motu Ultralite as well for sound output. I could maybe move that to USB but will have to try it first.


----------



## joeyfergie (Jan 11, 2012)

By the looks of the Motu Ultralite, it seems to have 2 firewire ports, to allow for daisy chaining. Getting a Firewire converter with a power supply will solve the power issue, and if I am able to run 2 cameras off a single bus I am sure you would be able to do 1 camera plus audio on a single bus.

On a side note, how well does the Motu Ultralite work? For our sound setup, we have a tower computer with 2 internal audio cards, and 2 USB cards, although I have always been looking at getting something like this that has multiple outputs.


----------



## anshu (Jan 11, 2012)

joeyfergie said:


> By the looks of the Motu Ultralite, it seems to have 2 firewire ports, to allow for daisy chaining. Getting a Firewire converter with a power supply will solve the power issue, and if I am able to run 2 cameras off a single bus I am sure you would be able to do 1 camera plus audio on a single bus.
> 
> On a side note, how well does the Motu Ultralite work? For our sound setup, we have a tower computer with 2 internal audio cards, and 2 USB cards, although I have always been looking at getting something like this that has multiple outputs.



Is the Ultralite MK3 which actually doesnt have the firewire outputs:
MOTU.com - UltraLite-mk3 Hybrid Overview

I think I'll be ok. The Ultralite is amazing, great internal control and beautiful output. I've done alot with it, recording and output, aside for the occasional pop from an overloaded computer I have no complaints.


----------



## joeyfergie (Jan 11, 2012)

Just looking at it as well. Must have seen pics of a different MOTU unit (that's where I saw the 2 firewire). It definitely looks like a good device, with many outputs. May have to put it on the wish list.


----------



## anshu (Jan 11, 2012)

joeyfergie said:


> Just looking at it as well. Must have seen pics of a different MOTU unit (that's where I saw the 2 firewire). It definitely looks like a good device, with many outputs. May have to put it on the wish list.



Indeed, just now have to find a hub. Shocked at the cost! I'm used to USB ones costing 5 bucks....


----------



## joeyfergie (Jan 11, 2012)

A firewire hub? How much does it cost? I have seen ones for under $40, which is pretty inexpensive. Never seen a USB hub for only $5 thou.


----------



## anshu (Jan 11, 2012)

joeyfergie said:


> A firewire hub? How much does it cost? I have seen ones for under $40, which is pretty inexpensive. Never seen a USB hub for only $5 thou.


 
Indeed found some for 40. Even one for 30.

USB HUB:

Amazon.com: Belkin USB 2.0 4-Port Ultra-Mini Hub (F5U407): Electronics


----------



## misterm (Jan 12, 2012)

we did this last year with a live production of "Dr. Horrible's Sing-A-Long Blog." We borrowed a camera from the broadcast dept and used QLab on my mac with the "Camera" cue and various video/audio cues.


----------



## museav (Jan 12, 2012)

joeyfergie said:


> I am working on a show right now that has something similar (but more complex) than this. In our production, we have 6 independently controlled 40inch TVs, 3 Live Cameras, as well as a bunch of video and image content. This is what we have:
> 
> All 6 TVs are connected via VGA to a Mac Pro. We have the graphics card upgrade, which gives us a total of 6 displays. The TVs are 1080p, but we are only using a resolution of 720p (less pixels needed to be generated by the graphics cards). We also have a USB Video card for the operator's monitor (costs about $50). Our 3 cameras are SD (realized unless you're sitting in the first row, you don't notice it is SD. We are taking the AV Out (composite), and running that through a standard RCA cable (If possible, I would go BNC, but that is too much money for us) into a Composite to Firewire Converter box. This converts the signal to Firewire, which is then readable by QLab using the Camera Cue. We have a second firewire card as well, as the onboard card did not handle 3 cameras well. All the camera and video cues are then put in the Qlab as normal, and everything is controlled through that. This way our Mac Pro, via Qlab is the one actually controlling all of the screens. Our show doesn't open for another 2 weeks, but we are running Q2Q's now, and so far no problems!


This probably explains why you noted such a large latency. For example, sending 720p to a 1080p device may save latency in the processing, which is apparently already converting a 4:3 aspect ratio/640x480 SD image to a 16:9 aspect ratio/1280x720 image, but requires latency at the display where it has to remap the non-native resolution to its native display resolution. And as already noted, adding converters or other processing is simply going to add additional latency. For example, going composite video out of the camera to a converter at the computer will likely entail latency at the camera to convert the digital video signal to analog composite video and then again at the converter to convert that back to digital. All of that latency is going to add up.



joeyfergie said:


> I have always noticed (a bit) of latency doing "live" cameras. With our current setup, the longest camera run we have is 100 feet. Going into Qlab then back to a TV (a 50 foot run of VGA), the delay is less than 1 second. Not really noticeable, unless you have someone clapping, etc (then you will have a AV sync issue, cuz the video will be behind the live audio). I have also done live video including a wireless camera, this time going to a projector. The sync time was about the same (closer to 1sec for the wireless camera).
> 
> All the times that I have done it, it is a case where only techies would notice a delay.


The cable lengths are irrelevant as the delays related to that are miniscule even at much longer lengths. However, 1 second of latency at 30fps is 30 frames of video and I've seen 3-6 frames, or 10% to 20% of that, generally suggested as the maximum latency before it becomes noticeable by the average viewer.

A related issue is lip sync. 1 second is 1,000ms and relates to sound traveling around 1,130'. So unless your audience is over 1,000' from the speakers, they would be hearing the audio before seeing the video with a noticeable delay. Even with shorter video latencies, you may need to delay the audio if lip sync is a factor.

Keep in mind that the application is the issue here. For actual image magnification, where you are showing a larger than life image of the live action in the same space, latency can be a significant factor. But if the image on the screen is more of a visual effect then any amount of latency may not be a relevant factor at all. Since your video is apparently from offstage, that should not be an issue except perhaps in terms of syncing any related audio.


----------

