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HDMI & HDCP

Last response: in Home Theatre
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September 14, 2004 9:59:30 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

I am attempting I understand HDMI and HDCP - attached are quotes
describing HDMI.

I want to make sure if I purchase a TV with only HDCP input, I will
have no issues down the road.

"HDMI extends the DVI standard and adds audio to it. Functionally it
is DVI for Video + HDCP for protection + Audio. "

"It is supposed to be backward compatible with DVI as well as existing
audio standards. For example, you will be able to take separate DVI
video + audio outputs from devices, combine them, and feed it into a
HDMI port on a TV. Or you can take HDMI output from a device, split it
and feed the DVI part to a TV and the audio part to a receiver."

Since I will be using a receiver for all my audio, I should be able to
purchase a TV with only HDCP (no HDMI) and any output device (HD cable
box for example) that has HDMI I should be able to send DVI/HDCP to my
TV and audio to my receiver.

Is there anything I overlooked where if I purchase a HDCP only TV I
will run into problems? The choices of HDMI TVs are more limited.


Thanks,

JCPZero

More about : hdmi hdcp

Anonymous
September 15, 2004 3:45:36 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

DVI and HDMI are the physical plugins, and HDCP is the methodology used to
prevent copying


Doug



"JP" <jcpzero@yahoo.com> wrote in message
news:6f915d52.0409141659.606a4aa0@posting.google.com...
> I am attempting I understand HDMI and HDCP - attached are quotes
> describing HDMI.
>
> I want to make sure if I purchase a TV with only HDCP input, I will
> have no issues down the road.
>
> "HDMI extends the DVI standard and adds audio to it. Functionally it
> is DVI for Video + HDCP for protection + Audio. "
>
> "It is supposed to be backward compatible with DVI as well as existing
> audio standards. For example, you will be able to take separate DVI
> video + audio outputs from devices, combine them, and feed it into a
> HDMI port on a TV. Or you can take HDMI output from a device, split it
> and feed the DVI part to a TV and the audio part to a receiver."
>
> Since I will be using a receiver for all my audio, I should be able to
> purchase a TV with only HDCP (no HDMI) and any output device (HD cable
> box for example) that has HDMI I should be able to send DVI/HDCP to my
> TV and audio to my receiver.
>
> Is there anything I overlooked where if I purchase a HDCP only TV I
> will run into problems? The choices of HDMI TVs are more limited.
>
>
> Thanks,
>
> JCPZero
Anonymous
September 15, 2004 8:30:38 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

jcpzero@yahoo.com (JP) wrote (in part):

>I am attempting I understand HDMI and HDCP - attached are quotes
>describing HDMI.
>
>I want to make sure if I purchase a TV with only HDCP input, I will
>have no issues down the road.
>
[Quotes deleted]
>
>Since I will be using a receiver for all my audio, I should be able to
>purchase a TV with only HDCP (no HDMI) and any output device (HD cable
>box for example) that has HDMI I should be able to send DVI/HDCP to my
>TV and audio to my receiver.
>
>Is there anything I overlooked where if I purchase a HDCP only TV I
>will run into problems? The choices of HDMI TVs are more limited.

You are misunderstanding the meaning of this alphabet soup,
particularly HDCP.

DVI (Digital Video Interface) and HDMI (High-Definition Multimedia
Interface) are similar standards for sending a digital signal from a
source (typically a digital tuner) to a display. HDMI uses a smaller
connector than DVI, and it may include audio, which DVI does not.
Either can be converted to the other fairly simply. Ideally, the
display would have both types of inputs (and the more the merrier).

HDCP (High-Definition Copy Protection) is an attempt to severely
restrict your ability to record programs. It works over either DVI or
HDMI to determine if the destination device is a "safe" one to send to
(an oversimplification, but close enough). You don't want it, but you
have to have it. If the source device has HDCP (most do, and
eventually all must) and the display does not, they will not work
together, at least not with a digital connection.

Since you don't plan to send sound to your TV it doesn't matter much
whether it has DVI or HDMI, but it should support HDCP to be
compatible with whatever you want to connect to it.

Del Mibbler <mibbler@nycap.rr.com>
Related resources
September 15, 2004 12:08:10 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

>
> DVI (Digital Video Interface) and HDMI (High-Definition Multimedia
> Interface) are similar standards for sending a digital signal from a
> source (typically a digital tuner) to a display. HDMI uses a smaller
> connector than DVI, and it may include audio, which DVI does not.
> Either can be converted to the other fairly simply. Ideally, the
> display would have both types of inputs (and the more the merrier).
>
> HDCP (High-Definition Copy Protection) is an attempt to severely
> restrict your ability to record programs. It works over either DVI or
> HDMI to determine if the destination device is a "safe" one to send to
> (an oversimplification, but close enough). You don't want it, but you
> have to have it. If the source device has HDCP (most do, and
> eventually all must) and the display does not, they will not work
> together, at least not with a digital connection.
>
> Since you don't plan to send sound to your TV it doesn't matter much
> whether it has DVI or HDMI, but it should support HDCP to be
> compatible with whatever you want to connect to it.
>
> Del Mibbler <mibbler@nycap.rr.com>

Thank you for the additional information. Bottom line seems to be, I
can purchase a current model TV with DVI connector as long as it
includes HDCP - I am not limited to only TVs with an HDMI connection.


JCPZero
Anonymous
September 15, 2004 11:17:53 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

JP wrote:
> "... you will be able to take separate DVI video + audio outputs from
> devices, combine them, and feed it into a HDMI port on a TV. Or you
> can take HDMI output from a device, split it and feed the DVI part to
> a TV and the audio part to a receiver."

No.

DVI is indeed video only, and HDMI can indeed carry audio and video,
but the audio and video are not carried on separate wires in the HDMI
connector, but rather are *mux-ed together* and sent over the same
wires.

The "combine" and "split" functionality requires an active circuit; it
cannot
be done by simply breaking out the wires in the HDMI cable.

Also, once A/V is mux-ed together and sent over the HDMI cable with
HDCP encryption applied, I believe there are rules that may prohibit
downstream devices/circuits from de-muxing the A/V and exposing the
A in an unprotected form, like say SPDIF.

Fortunately most if not all devices that have HDMI inputs and outputs also
have dedicated audio inputs and outputs.

Thomas Gilg
Anonymous
September 15, 2004 11:40:47 PM

Archived from groups: alt.tv.tech.hdtv (More info?)

Del Mibbler wrote:
> HDCP (High-Definition Copy Protection) is an attempt to severely
> restrict your ability to record programs.

HDCP (High-bandwidth Digital Copy Protection) (see
http://www.digital-cp.com) is only about creating a secure and trusted link
between two devices.

Within the US, we have 3 primary digital rights management concepts:

* access control - can you see it. Examples include the cable company wiring
you up, or a satellite company giving you a SmartCard to insert into your
set top box.

* copy control - can you copy it. Examples include Macrovision, which all
recording devices in the US built after 199x are required to look for, and
if it is present in the video signal, refuse to record, and the Copy
Generation Management System (CGMS-A and CGMS-D) which can specify "copy
never", "copy once", "copy no more" and "copy freely".

* redistribution control - can you redistribute it. The big example here is
the Broadcast Flag (BF), whos primary intent is to prevent broadcast content
from being redistributed to the internet. Lots of people think the BF is
about copy control, it is NOT. Unfortunately, not all the implementation
details for the BF have been figured out, much less what forms of
"redistribution" should be prohibited, and what devices need to be the gate
keepers.

Getting back to HDCP. When there is no access, copy or redistribution
control bits/signals set, source devices tend to turn HDCP off. When one or
more copy, redistribution or control bits/signals are set, HDCP is typically
turned on so that the source devices can transmits the
A/V/access-bits/copy-bits/redistribution-bits over to the destination device
faithfully, without alteration. Assuming the source device trusted the
destination device to begin with (part of the HDCP handshake) and communited
all the A/V/access-bits/copy-bits/redistribution-bits, then it becomes the
responsibility of the destination device to interpret all the
access/copy/redistribution bits and behave correctly.

To put all this another way. Devices enforce access, copy and
redistribution. DVI and HDMI with HDCP, and for that matter IEEE-1394 and
USB with DTCP, just provide secure trusted links for the devices to chat
over.

Thomas Gilg
Anonymous
September 16, 2004 12:20:27 AM

Archived from groups: alt.tv.tech.hdtv (More info?)

I wrote:
> Devices enforce access, copy and redistribution. DVI and HDMI with HDCP,
> and for that matter IEEE-1394 and USB with DTCP, just provide secure
trusted
> links for the devices to chat over.

I think I errored for HDCP. Feedback welcome.

Once any content is HDCP'ed, it appears that one interpretation is that all
downstream "Presentation" and "Repeater" devices are at most allowed to
make temporary copies.

Thomas Gilg
!