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Clarify inputs and outputs are video sources and sinks.
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Morphit
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Your assumption that the KVM is a passive component is wrong. Even with VGA, the KVM has to correctly manage access to the EDID in the monitor. The inputsvideo sources cannot read the monitor EDID simultaneously. However the video signals are totally analog so once the inputssources know what format to send, they can be switched in and out as needed.

DVI (the digital part) is not just unidirectional signals, there is a whole protocol that requires timing synchronisation on both sides of a link. On top of that is HDCP where encryption keys need to be synchronised.

There might be some clever trickery to reset the links every time the inputvideo source is switched, but I think the normal way to do this is to decode the input video data in the KVM, then re-encode for the monitor. This means the links to the monitor and video inputssources needn't be reset all the time. However, to do this you need a rather powerful FPGA (or bespoke ASIC) to at least maintain multiple input links and to forward the right video data to the output links.

In addition to all that, I'm sure there's a lot of testing to iron out quirks in different devices. These are probably widely known for VGA, but not so much for DVI.

Your assumption that the KVM is a passive component is wrong. Even with VGA, the KVM has to correctly manage access to the EDID in the monitor. The inputs cannot read the EDID simultaneously. However the video signals are totally analog so once the inputs know what to send, they can be switched in and out as needed.

DVI (the digital part) is not just unidirectional signals, there is a whole protocol that requires timing synchronisation on both sides of a link. On top of that is HDCP where encryption keys need to be synchronised.

There might be some clever trickery to reset the links every time the input is switched, but I think the normal way to do this is to decode the input video in the KVM, then re-encode for the monitor. This means the links to the monitor and video inputs needn't be reset all the time. However, to do this you need a rather powerful FPGA (or bespoke ASIC) to at least maintain multiple input links and to forward the right video data to the output links.

In addition to all that, I'm sure there's a lot of testing to iron out quirks in different devices. These are probably widely known for VGA, but not so much for DVI.

Your assumption that the KVM is a passive component is wrong. Even with VGA, the KVM has to correctly manage access to the EDID in the monitor. The video sources cannot read the monitor EDID simultaneously. However the video signals are totally analog so once the sources know what format to send, they can be switched in and out as needed.

DVI (the digital part) is not just unidirectional signals, there is a whole protocol that requires timing synchronisation on both sides of a link. On top of that is HDCP where encryption keys need to be synchronised.

There might be some clever trickery to reset the links every time the video source is switched, but I think the normal way to do this is to decode the video data in the KVM, then re-encode for the monitor. This means the links to the monitor and video sources needn't be reset all the time. However, to do this you need a rather powerful FPGA (or bespoke ASIC) to at least maintain multiple input links and to forward the right video data to the output links.

In addition to all that, I'm sure there's a lot of testing to iron out quirks in different devices. These are probably widely known for VGA, but not so much for DVI.

Source Link
Morphit
Morphit
  • 704
  • 5
  • 9

Your assumption that the KVM is a passive component is wrong. Even with VGA, the KVM has to correctly manage access to the EDID in the monitor. The inputs cannot read the EDID simultaneously. However the video signals are totally analog so once the inputs know what to send, they can be switched in and out as needed.

DVI (the digital part) is not just unidirectional signals, there is a whole protocol that requires timing synchronisation on both sides of a link. On top of that is HDCP where encryption keys need to be synchronised.

There might be some clever trickery to reset the links every time the input is switched, but I think the normal way to do this is to decode the input video in the KVM, then re-encode for the monitor. This means the links to the monitor and video inputs needn't be reset all the time. However, to do this you need a rather powerful FPGA (or bespoke ASIC) to at least maintain multiple input links and to forward the right video data to the output links.

In addition to all that, I'm sure there's a lot of testing to iron out quirks in different devices. These are probably widely known for VGA, but not so much for DVI.