pass thru video output on LCD monitors

[wpshooter]

I am seeing what appears to be a pass thru analog output connection on an LCD monitor that we have here in our office.

Can that connection be used to pass thru the video signal from another/second LCD monitor ?

When I connected the analog connector from the other/second monitor to this pass thru connector, the NO SIGNAL message that was being displayed on the second monitor disappear BUT the video from the first monitor that was connected directly to the computer's video card, was not also displayed onto the second monitor.

Is there perhaps somewhere in the first monitor's configuration that this pass thru connector has to be enabled ?

Thanks.

 

[Modelworks]

I haven't seen a monitor with an output for another monitor before. I think what you are seeing is an alternate input. Some monitors come with DVI and analog inputs.

The reason the second monitor would change from no signal is because monitors use a signal method called I2c to determine if a signal is present. They don't actually decode the signal at this point, they just see that there is voltage present on the pins. When you connect it to another monitor those pins go high and it assumes there is something there.

 

[wpshooter]

I haven't seen a monitor with an output for another monitor before. I think what you are seeing is an alternate input. Some monitors come with DVI and analog inputs.

The reason the second monitor would change from no signal is because monitors use a signal method called I2c to determine if a signal is present. They don't actually decode the signal at this point, they just see that there is voltage present on the pins. When you connect it to another monitor those pins go high and it assumes there is something there.

Yes, what you said finally dawned on me this evening, daaaaaaaaaaahhh.

But this triggers another question.

Is there any real/practical performance difference in using the DVI inputs/connections as compared to the analog inputs/connections ? If you have the option to use the DVI instead of the analog should you always use the DVI or are there certain circumstances wherein the analog would be preferable over the DVI ?

And if the DVI is the preferred, is it dependent upon the complexity of the graphics of the software being run ?

Thanks.

 

[alaricljs]

DVI is preferred on any non-CRT monitor since it's transmitting Digital Video. So you are taking digital information from the GPU/vidcard, sending it down the wire to the monitor and it's slicing and dicing that data as needed and tossing it into the panel controller.

If you use an analog signal that means you are taking the digital info from the GPU/vidcard, converting it to analog, sending it over the wire to the monitor which then takes the analog and converts it to digital and shoves it onto the panel.

analog transmission and conversions are lossy.


Short version: use DVI.

 

[wpshooter]

DVI is preferred on any non-CRT monitor since it's transmitting Digital Video. So you are taking digital information from the GPU/vidcard, sending it down the wire to the monitor and it's slicing and dicing that data as needed and tossing it into the panel controller.

If you use an analog signal that means you are taking the digital info from the GPU/vidcard, converting it to analog, sending it over the wire to the monitor which then takes the analog and converts it to digital and shoves it onto the panel.

analog transmission and conversions are lossy.


Short version: use DVI.

Can you switch from use of analog to use of DVI without making any software/configuration/driver change, i.e. is it just a matter of changing from analog connector to DVI connector, or does connection that is going to be used need to be IN PLACE when operating system is installed ?

Thanks.

 

[betasub]

^ It is all handled transparently to the user, by the hardware (& drivers). No changes in config settings should be required, although the monitor may have an manual option to choose which input to display if you have connections to more than one.

 

[wpshooter]

^ It is all handled transparently to the user, by the hardware (& drivers). No changes in config settings should be required, although the monitor may have an manual option to choose which input to display if you have connections to more than one.

So are you saying that at the time the operating system is install that the drivers that are installed include the ability to use either analog or DVI, not just what is "plugged in" at the time the O/S is being installed ?

Thanks.

 

[alaricljs]

That's what he's saying. I don't have anything modern to test with, but if you do it with the computer off it will come up displaying on whatever screen is plugged in. If you do it with the machine on you generally will have to use the control panel to tell it to output to the new connection.

 

[wpshooter]

That's what he's saying. I don't have anything modern to test with, but if you do it with the computer off it will come up displaying on whatever screen is plugged in. If you do it with the machine on you generally will have to use the control panel to tell it to output to the new connection.

That's what I thought, just wanted to ask to make sure.

Sure wouldn't want to reinstall O/S and/or graphics drivers.

Thanks for the reply.