AVS Forum banner
Not open for further replies.
1 - 1 of 1 Posts

17 Posts
Discussion Starter · #1 ·
PC to RPTV HDTV's using DVI with HDCP

I am starting to think that the HDCP circuitry may be contributing to the reasons why trying to use my PC using a RPTV HDTV via the DVI-D inputs at resolution above 640 x 480p is not working as expected.


I remember when I was shopping for an HDTV that I read amny articles concerning content protection schemes. Non DVI/HDCP connectable devices would be able to display the HD content, but only at the lower res of 480p, because the HDCP transmitter would tell the TV to do this.

This was a good reason to get a TV with DVI/HDCP for watching DVD and HD-VHS. Wasn't it?

But what about using the PC at full res? How is PC to TV affected by this?

Technical References:

This article appears to be a pitch to TV makers concerning the need for DVI/HDCP on their products by a certain HDCP transmitter manufacturer.


The following excerpt from this article follows serveral paragraphs which outline what is needed to provide DVI/HDCP for applications such at HD-STB, HD-DVD and VHS players, etc. This excerpt touches on the differences between the above named devices and the PC.

A personal computer is completely different, though. Users frequently install their own software and can download new drivers or plug-ins with just a few mouse-clicks. In this environment, upstream authentication combines hardware and software protocols that include encryption and signature algorithms, with the implicit assumption that no driver is trustworthy. Special cryptographic messages that only the software can interpret hide link status and confidential data values. The drivers can only pass the messages along. If the drivers fail to forward the messages or tamper with them in any way, the mischief will be detected.

Here is an excerpt from the same article describing what is needed for a graphics adapter to comply with HDCP. This brings up the question.

What if the current batch of DVI-I out video cards are not designed to send what the HDCP tranmitter wants to see?

Adding an HDCP-capable DVI output to a product such as a graphics adapter or set-top box is a similar exercise. You still need to add the interface silicon, the nonvolatile key memory, and the DVI connector. The circuit complexity is similar to that shown for the receiver. In general, though, the output-side components are not self-contained. HDCP hosts must control the interface and the information exchange. This requirement typically adds software or firmware. The functions aren't complex, but they do add to the development and test effort.

Please look at the article and links to the schematics and tell me if you agree or disagree that the signal from the PC to the DVI to the display must go through this HDCP transmitter first. If you agree, then isn't it possible that the HDCP transmitter is interfering with the PC via DVI.

Please confine your replies to specific thoughts which might can help solve this problem or explain technically why this is not a valid concern. Please provide links to technical references if you have it.

Thanks so much,


Toshiba 42HDX82 dvi-d in, GF4 Ti 4200 dvi-i out
1 - 1 of 1 Posts
Not open for further replies.