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With HDMI cables being symmetric and male-male, it is possible to connect two different HDMI output ports to each other, such as a DVD player to a laptop's HDMI output. What would happen if I were to actually connect two devices like this and turn them both on? Would it damage the laptop and/or DVD player, do nothing, cause problems until I unplug the cable, or what? Would it be possible to download drivers to the laptop to actually let me use the HDMI port as video/audio input, and if so, where could I find these drivers?

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2 Answers 2

The two devices will attempt to handshake with each other. Since they are both output devices, they will not communicate. Fortunately, no damage will occur, the engineers figured people would attempt to do this. You can not change an input to an output, or an output to an input. Their direction is hardware bound, and can not be modified with software.

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This is what I figured would happen, but could you provide a source for this? –  Daniel H Jun 9 '13 at 18:20

Would it be possible to download drivers to the laptop to actually let me use the HDMI port as video/audio input, and if so, where could I find these drivers?

It would depend on the laptop hardware, but I seriously doubt that such functionality exists in any consumer hardware. For an analogy, see USB Host Mode. USB as implemented on most consumer electronics (such as the Android link) is done in Client mode, but if the hardware supports it it can be used in a different mode. This is possible because, like HDMI (and the reason for the analogy) is that both sides of the connector could be (not necessarily are) the same physical design.

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So it won't work, but will it cause any actual problems? Could you cite sources for the host/client mode thing also? Random unreliable stories on the internet seem to say that it won't work, which I expected, but one also seems to say the hardware is damaged, which I did not. Obviously I can try it myself to see if anything breaks, but for obvious reasons I would prefer not to do that. –  Daniel H Jun 11 '13 at 17:54
    
If it causes damage, then that is a fault of the hardware, or faulty hardware. Where did you see the "It broke" link? I'd like to read that. –  dotancohen Jun 11 '13 at 19:22
    
As I said, it was an unreliable story I saw somewhere. The person who had this problem said only a few sentences and didn't seem particularly knowledgeable; it seems likely that the problem was unrelated. If you're still interested, the link is en.kioskea.net/forum/…, search for "repair". –  Daniel H Jun 11 '13 at 20:01

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