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SX20 VGA input


We connected Y-cable to DVI-I input of SX20 that splits the DVI-I input to DVI and VGA ports.

When we connect a laptop with VGA output to the SX20 TC6.3.0 through the Y-cable, we have two issues:

1) The PC does not detect what "monitor" is connected to it and what resolutions it supports.

2) SX20 does not accept or understand Full HD resolution from VGA input.

Issue #1 seems logical: the Y-cable directs DVI-I DDC clock and data pin to DVI-D input, not VGA. Therefore EDID information does not go from SX20 to the PC over VGA.

Issue #2 is the actual problem. Users may want to display their presentation at Full HD mode (at least for off-line presentations) but SX20 does not undestand the signal. For example, 1680 x 1050 resolution is accepted without a problem.

When I remove the Y-cable from DVI-I input and use DVI-VGA adapter instead then everything works as expected.

There was also VGA cable installed in the room from the conference table to the equipment cupboard. When we connected PC through the installed cable and DVI-VGA adapter to the SX20, we experienced similar problem: EDID information was not present AND it was impossible to display Full HD resolution. When I connected a monitor through the same VGA cable (instead of SX20) then EDID information was not present but the monitor was able to display 1920 x 1080 @60 image without any problems.

So: it seems that when the PC unable to receive EDID information over VGA from SX20 then SX20 is not able  to display VGA image with Full HD resolution.


Could it be "fixed"?

For testing, I connected the PC also to DVI-I input of C60. The latter does not have such a problem. It is able to receive Full HD image in spite of EDID signal.

Thank you in advance,


Cisco Employee

Re: SX20 VGA input

Hi Marko,

The SX20 supports the Visca protocol so the camera cable is different. Its always best to use DVI-VGA cable shipped along with it for content sharing.

For related information please refer :

C20 and SX20 Camera Cable | Cisco Technical Support Forum

using converter to connect presentation cable to SX20 codec | Cisco Technical Support Forum

Thanks and Regards,



Re: SX20 VGA input

Should I rephrase my question?

I did not ask about camera cable nor which VGA cable to use.

I asked why is SX20 unable to input 1920 x 1080 image over VGA cable in case the PC does not receive DDC signal?


Re: SX20 VGA input

Hi Marko,

You're question is perfectly sound, I think Geevarghese misinterpreted the question, as we use Y-cables to split signals connected to the camera.

To answer your question regarding the DVI-I input on the SX20: How is the input configured? If set to auto, we will not support Y-cables connected to the DVI-I input. The official DVI standard supports both digital and analog signals, but in most cases the default  AutoDetect setting can only detect whether the signal is analog RGB or digital. In cases where DVI-I cables are used (these cables can carry both the analog and digital signals) the auto detection fails if signal splits, and you will get these kinds of issues. In other words, your split cable will not carry both analog and digital EDID.

I strongly recommend that you do not use split cables when using autodetection, and this not supported by Cisco.

Kind Regards,



Re: SX20 VGA input

Hi Jonas,

Yes, I understand that EDID signal does not go through split cable to both inputs.

However, it does not make me any sense why SX20 is unable to receive 1920 x 1080 VGA signal in case EDID signal is missing?

It happens also without Y-cable, over ordinary DVI-VGA adapter in case EDID signal does not go through (pin 12 or 15 disconnected).

At the same time SX20 is able to receive all resolutions up to 1680 x 1050 over VGA without EDID signal.

And C60 is able to receive resolutions up to 1920 x 1200 over VGA without EDID signal.



Cisco Employee

Re: SX20 VGA input

Hi Marko,

The EDID signal tells the computer what input the codec is able to receive. It looks like the standard output the PC outputs without any EDID is not compatible wit the SX20. The C60 uses a different architecture and hence that can explain why it works there. The problem is that there is many variants of 1080p; refresh rates, reduced blanking, color space etc. When the EDID is received by the PC, the PC will deliver a compatible format.

Best regards



Re: SX20 VGA input

I found this blog and I'm hoping you can provide some additional insight.  Is it possible to connect a video switch/scaler to the SX20 (e.g. Extron DCS 301 HD or the Kramer VP-426) or will this be problematic?  I'm looking for a solution that will provide both VGA and HDMI connectivity without having to swap cables/adapters etc. 

Re: SX20 VGA input

I will talk about my scenario.
We are using the nds-SS41 as our video switch, in inputs the user can connect a VGA or HDMI cable and the nds-SS41 converts one of these inputs to a single HDMI output, this output connect an HDMI cable and an HDMI converssor connector to DVI. In the first sx20 installed sometimes it worked on a particular computer VGA worked not cool. In another identical facility with SX20, even connecting the HDMI directly from my computer and coverssor connector dvi SX20 does not detect sinal.Como make this scenario work? change the DVI input configurations in digital SX20, auto, analog.
How was unable to operate using the HDMI to DVI connector converssor I used an HDMI to VGA converssor and the original VGA DVI cable cisco and it worked. But I need you to work with HDMI DVI connector and no VGA HDMI converssor

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