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[Cliff Jeffrey]

I am looking for an inexpensive way to switch between 2 computers on one projector.

This past Sunday we had a guest speaker who wished to use his own laptop. When we tried to unplug the vga cable from our laptop and plug into his we had trouble and the projector could not find the vga inout. He had to powerpointless!


Thanks for any help.

[Brad Weber]

That would be a switcher and more specifically, a VGA switcher.

My guess is that your guest's laptop did not have the external display port active.  Typically one of the function keys on a laptop toggles between internal display only, external display only or both and if he started his laptop with no display attached it may have defaulted to the internal display only state.  This is probably the most common cause for not being able to get a projected display from a laptop.

There is always the chance that they were running display settings that your projector was unable to handle or recognize, but that is much less common than it used to be.

[Cliff Jeffrey]

Any recommendations? Nothing fancy needed.

[Daniel Cash]

For our churches rear projector that we uses for lyrics on the back wall. (only visible to the worship team on stage; not the congregation) we use one of these:

 http://www.monoprice.com/products/product.asp?c_id=101&c  p_id=10106&cs_id=1010601&p_id=54&seq=1&forma t=2

We have never had a problem with it, and we have used many miscellaneous computers and laptops with it (mac and pc). For $5 you really cant go wrong. When switching, the transition for a very brief moment can look a little off or the projector might go blank... so you might want to pay of for something that offers a better transitions (buffered?)  I don’t have experience with a more  advanced product like that.

-Dan

[Brad Weber]

Daniel Cash wrote on Tue, 22 January 2008 17:49

When switching, the transition for a very brief moment can look a little off or the projector might go blank... so you might want to pay of for something that offers a better transitions (buffered?)  I don’t have experience with a more  advanced product like that.

Given the cost, that box is probably simply a physical switch.  Whenever the sync component of a signal changes or sync is lost even momentarily, such as is common with switchers, the projector has to 'resync' to the new signal and that is the momentary blank and/or artifacts you see.  The most common way to avoid that is through switching sources using an external switcher/scaler or seamless switcher as these devices provide a constant stable sync to the projector, thus allowing cleaner transitions between sources.  However, they are a little more expensive than that switch box!

[Greg Hertfelder]

Powerpointless!

You just described Corporate America in one concise word. This was the best belly laugh I've had in weeks!

The problem with laptops is that they typically boot up in power-conservation mode, which is with the external VGA port powered off. And with many laptops, if they don't sense a 75-ohm load (monitor or projector) upon power-on, they won't switch on the external port. So, even with a mechanical switch as suggested by Daniel, trouble could be ahead if the switch wasn't in the correct position upon power-on.

I know this isn't the answer to your question, but I would recommend that you keep a $20 flash drive around and use the drive to copy the PowerPoint file to the normal computer and run all the PowerPoint presentations from one computer. It's far more reliable than "the switch" - unless you spend a couple thousand on a switcher-scaler, which was previously suggested.

Power corrupts. PowerPoint corrupts absolutely.
-
-

[Arnold B. Krueger]

Daniel Cash wrote on Tue, 22 January 2008 22:49

For our churches rear projector that we uses for lyrics on the back wall. (only visible to the worship team on stage; not the congregation) we use one of these:   http://www.monoprice.com/products/product.asp?c_id=101&c   p_id=10106&cs_id=1010601&p_id=54&seq=1&forma t=2 We have never had a problem with it, and we have used many miscellaneous computers and laptops with it (mac and pc). For $5 you really cant go wrong. When switching, the transition for a very brief moment can look a little off or the projector might go blank... so you might want to pay of for something that offers a better transitions (buffered?)  I don’t have experience with a more  advanced product like that.

We're doing video on a shoestring, and video switchboxes is one place where you can spend a lot of money, and get something for it.

Boxes like this not only provide ugly transitions, they can trash the signal even when you aren't switching. The problem is the wiring inside the box. It does not maintain the impedance of the coax, and generally causes ringing and fringing around sharp transitions, like text.

If it works for you - great! But, if you have a good sharp projector, and in particular if your cable lengths are more than a few feet, you will see the fringing due to ringing and standing waves in the video cable, due to the lack of a proper impedance match through the box.

Our projectors are a Panasonic 5500 on the ceiling, and a Canon that duplicates the same image on the wall behind the balcony. We have about to transmit video over about 200 feet worst case.

We switch between our Powerpoint computer in the sound booth, and the pastor's laptop in the middle of the service. When we do baptisms, we have a close-up camera for the baptistry, which we scale to VGA with an inexpensive scaler. So, we can have to do several switches of the VGA input of our projector during a service. Using the projector's internal switch is ugly because its dialogs show on-screen when you switch.

We started out with a simple mechanical switch a number of years ago when we got a new pastor that wanted to run his own powerpoint for his sermons. This actually sort of worked with our old Eiki projector because its resolution was not all that good in 1024 x 768 so the ringing was not that noticable. It also would resynch almost immediately after a switch-over.

When we upgraded to the Panasonic, we knew we were in trouble right away because it made the ringing in the switchbox very obvious, and it took a long time to resynch after every switchover. You don't want to be the person doing the switch in the middle of a baptism service when it takes maybe 20 seconds for the projector to stabilize.

There are purpose-built VGA mechanical switches that preserve impedances well enough for a clear picture. But they don't do a lot about a projector that takes a while to resynch.

We eventually found a device called a black interval switch that provided very clean transitions. However when we upgraded our Powerpoint computer, the synch from the new video card did not match the synch from the pastor's laptop well enough to allow it to avoid the problem with the projector blanking. I've tried every concievable tweek on the video in both machines to bring things back in line and some video card swaps, without success. I suspect this is why black interval switches are not all that popular.

The high road is to use a scaler with multiple inputs. Other churches in the area who have them have none of the problems that I have had with the black interval switch. Trouble is, that instead of paying $6 for a simple mechanical switch, or $40 for a mechanical switch that preserves impedances, or $500 for a black interval switch, you're talking well over $1,000. Dpending on quality, features, and number of inputs and outputs, you could be talking the price of a good video projector - $6,000 or more. Common brands of high performance scalers include Kramer, Extron, and Barco.

Right now we are expanding our video distribution network again, to cover a number of remote locations. My plan is to convert the whole system to HDMI. It will be interesting to see what can be done on our budget - which is a well-stretched shoestring.

[Brad Weber]

Arnold B. Krueger wrote on Sun, 03 February 2008 08:27

My plan is to convert the whole system to HDMI. It will be interesting to see what can be done on our budget - which is a well-stretched shoestring.

Out of curiosity, why HDMI?  HDMI is a consumer format and is greatly driven by the fact that it incorporates the Digital Rights Management (DRM) that content producers and distributors want to see implemented in consumer devices.  It is not really a professional, production or broadcast format.  How many people bought into DVI which is already pretty much being replaced by HDMI and I would also be concerned that by the time many people could complete a transition to HDMI, it will be replaced by the next great consumer format.  If you want high def in a non-consumer application, you might think about HD-SDI and/or RGBHV.

[Arnold B. Krueger]

Brad Weber wrote on Sun, 03 February 2008 20:03

Arnold B. Krueger wrote on Sun, 03 February 2008 08:27 My plan is to convert the whole system to HDMI. It will be interesting to see what can be done on our budget - which is a well-stretched shoestring. Out of curiosity, why HDMI?  HDMI is a consumer format and is greatly driven by the fact that it incorporates the Digital Rights Management (DRM) that content producers and distributors want to see implemented in consumer devices.  It is not really a professional, production or broadcast format.  How many people bought into DVI which is already pretty much being replaced by HDMI and I would also be concerned that by the time many people could complete a transition to HDMI, it will be replaced by the next great consumer format.  If you want high def in a non-consumer application, you might think about HD-SDI and/or RGBHV.

I agree with the facts you present. HDMI *is* a consumer format. I don't know how long it will last as the mainstream video interconnection format, but my intuition says that it will last  long enough for my purposes.

As far as RGBHV goes, it has two things going against it for me. First off, I already have RGBHV implemented. It is our current means for doing hi rez video distribution. The second thing that is wrong with it is that it is analog. RGBHV cabling for long distances is bulky and needs exta cables for audio. Or, one can use CAT 5/6 as RGBHV transmission media by means of converters which cost about the same as similar facilities for HDMI.

As far as HD-SDI goes, its big problem is that it violates my budgetary constraints. It looks to me like the sort of components I need will cost 3-4 times more as HD-SDI components than as HDMI. Furthermore a lot of the components I need to use like displays and video cards come with DVI inputs and outputs for low base prices. Converting DVI to HDMI or vice versa takes an $8.00 commodity adapter.

Correct me if I'm wrong but it appears that the cost of  DVI-to-HD-SDI or the reverse conversions  costs literally 100's of times more than DVI-to-HDMI, or the reverse. HD-SDI video cards, projectors, and displays are rare and expensive.

It looks to me like HDMI will last at least 3-5 years as the mainstream format video distribution format because all sorts of consumer manufacturers are still implementing new equipment with it. I expect the cost of scalers, DAs, and switches to continue go down from their already low prices.

To put the sort of cost constraints I work under into perspective, for 2 years I've done everything I've done with a $400 per month budget, with very very infrequent approvals for big ticket items like video projectors an the digital mixer. For example, I implemented very basic DMX theatrical and architectural lighting for a 5,400 square foot sanctuary using existing ca. 1955 lighting fixtures and that $400 per month funding for about 4-5 months.

[Cliff Jeffrey]

Greg Hertfelder wrote on Sun, 27 January 2008 17:59

Powerpointless! You just described Corporate America in one concise word. This was the best belly laugh I've had in weeks! The problem with laptops is that they typically boot up in power-conservation mode, which is with the external VGA port powered off. And with many laptops, if they don't sense a 75-ohm load (monitor or projector) upon power-on, they won't switch on the external port. So, even with a mechanical switch as suggested by Daniel, trouble could be ahead if the switch wasn't in the correct position upon power-on. I know this isn't the answer to your question, but I would recommend that you keep a $20 flash drive around and use the drive to copy the PowerPoint file to the normal computer and run all the PowerPoint presentations from one computer. It's far more reliable than "the switch" - unless you spend a couple thousand on a switcher-scaler, which was previously suggested. Power corrupts. PowerPoint corrupts absolutely. - -

Good idea, Will do that.
May not work when the presenter wants to use his own computer, not ours and when it is Mac and we run PC.

So what is the least expensive decent option we could do?
This is a church of 70 people.

[ProSoundWeb Community]