Effect of cable length on projector inputs

[Johnno]

Hello everyone, greetings from sunny Blackpool (except it's been p*ss*ng it down all day)

 

For the school play at Easter the Drama Queen wanted to project her backdrops from a laptop so I bodged a projector cradle and hung it from the FOH centre pipe and projected onto the cyc wall to great success.

 

The signal was supplied to the proj by an AEI DV200 DigiSender which only lost contact once in the three shows. This resulted in a bright purple manufacturer's logo screen suddenly appearing. Everyone giggled, but so what! It's no different to any other hiccup in a production. We'll survive.

 

I'm now looking into a more permanent installation. If I was to have a proj screwed to the ceiling and fed by a cable from the control area which of the possible inputs to the proj would you expect to cope best being fed from a cable run of about 70 feet? The inputs available are composite video, S-Video, component video and Computer Monitor connection. Or is there likely to be nothing in it as all would be equally dire and I should stick to the radio link.

 

On a different point the DV200 would not allow a PowerPoint slide to be a video clip. The laptop showed it but the projector only showed its first frame. I spoke with the vendors who were aware of this shortcoming but could not offer a reason for it. Has any anyone here come across this? It shouldn't happen as the transmitter is simply broadcasting the output from the laptop's video port which is exactly what its screen is showing.

 

Regards,

 

John.

[Pete McCrea]

70' is only 21.something meters. Sending VGA would be fine over that distance. It may require a Line Driver with a bit of EQ to compensate for any losses/interence. We regularly work over that length with VGA cabling. And to be honest you'd probably be able to run all the signals over that length anyway. Although for cleanlyness I'd aim to get a scaler and take the video upto VGA/XGA resolution and do any switching in the scaler, giving a continuous Data feed to the projector to avoid any blue screen 'input 1' moments.

 

I always stay clear of radio links unless I absolutely have to. Give me a wire any day.

[dosxuk]

On a different point the DV200 would not allow a PowerPoint slide to be a video clip. The laptop showed it but the projector only showed its first frame. I spoke with the vendors who were aware of this shortcoming but could not offer a reason for it. Has any anyone here come across this? It shouldn't happen as the transmitter is simply broadcasting the output from the laptop's video port which is exactly what its screen is showing.

 

This will be the laptop - a lot of laptops (and PC's) will have a primary graphics device (normally the built-in screen on laptops) which will show everything. If the video out is not a 'clone' of the primary device, it will not show any content which is 'overlayed' in hardware.

 

The easiest way around this is to change your?graphics settings to make you video out the primary device (which will in turn mean you won't see the videos on the laptop screen). Some laptops / PC's have a 'Clone' option, where the two?outputs are driven?the same (which introduces issues with resolution and refresh rates - hence it not normally being the default), which would allow you to see the same on both outputs.

 

We run a 30m VGA lead?to our projector, as well as a 15m composite and 15m s-video, and we don't have any problems with either. Over those sort of distances, I wouldn't even contemplate running it over a radio link unless absolutely absolutely neccessery! I'd also be looking at your projector options to see if you can turn off the logo screen when it looses an input! That way, if you have to do something like reboot your laptop during a show, you won't have the start up screens projected all over stage.

[Tomo]

Over standard VGA cable, you can go approximately 20-30m before you start to lose clarity at 1024x768.

The issue you get is 'smearing' - any sharp vertical edges in the image get smudged out a little.

 

If the audience are a fairly long way away from the screen, you may be able to go up to 50-60m before the smearing becomes too much.

 

The issue with embedded Powerpoint video is caused by DirectX - video overlays can only exist on one physical output, which means that you can display the video on the local screen OR the external monitor, but not both.

The best way around this is to use Extended Desktop, rather than Clone mode.

Set Powerpoint to display the presentation on the secondary monitor, and activate Presenter view - this gives you a useful display on the laptop, showing the current slide and the next two or three, and the proper slide on the external monitor - in this case, the projector.

[beware]

our survey says eh er!!.

 

to display videos on both screens, goto display properties, (right click desktop, properties, Settings), click advanced, then troubleshooting, then drop the hardware acceleration down by one or two notches.

 

Works everytime for me.

 

Ben

[Tomo]

to display videos on both screens, goto display properties, (right click desktop, properties, Settings), click advanced, then troubleshooting, then drop the hardware acceleration down by one or two notches.

Really?

Which graphics cards did this work for - would be very handy!

[beware]

it works on all laptops I've ever used in the conference centres. even the annoying Nvidia cards.

[Johnno]

Thanks for your comments and suggestions.

 

I'm quite pleased that the cable length shouldn't be a problem as I prefer wires to wireless.

 

I'll pass your computer suggestions on to the fellow I spoke to about the problem, see what he thinks.

 

Regards,

John.

[peternewman]

Something that's potentially of use (in one of the current CPC offers brochures), Cable and Faceplate Assembly basically a variety of connectors in a metal box with all the relevant cabling breaking out at the other end for the projector. Will probably save some of the hard work if you want to run VGA, Composite, S-Video etc. Available in 10m (AV12254) and 15m (AV12390) varieties. Note I've not tried these, merely saw them in the catalogue and thought they might be useful.

 

HTH

 

PN

[dbuckley]

it works on all laptops I've ever used in the conference centres. even the annoying Nvidia cards.

Indeedy.

 

Overlay is a feature supported in some video cards in hardware, and if the driver supports the feature then Windows will use that feature. If the driver doesnt support that feature, or if you instruct Windows not to trust the driver (which is what cranking down the accelleration features do) then Windows will do it all in software. Of course, you are burning CPU cycles to do a job that can be offloaded, but given the raw power of modern computers thats not really an issue.

[Chris Beesley]

The cable assemblies we sell are designed for the Interactive Whiteboard installers - they save hours of engineer time.

 

Regards

 

Chris Beesley

Product Manager

CPC

[maeterlinck]

Passing the processing load off to the CPU will work for some things, but be I'd be careful with this in general. There is a lot of work done to render an image, work that the GPU are designed to do specifically. You should normally find that if a video doesn't appear on the cloned or second screen then there will be an option in the Advanced config for the graphics card about overlay, directx etc.

But I've normally only seen this behaviour in the lower end cards.

 

Cable lenght should be fine. Maybe also run in a bnc at the same time so you can run video direct, can be useful in certain situations and cheap to do.

[Ekij]

It may also be useful to run an RS232 from the laptop to the projector, most projectors can have their display frozen, blanked etc from simple commands sent over RS232. Especially if you intend to run the two displays (projector and laptop) as two separate screens (you won't want the application that controls the commands over RS232 to appear on the projected image).

 

Projector control application

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