Does quality degrade if connecting HDMI-HDCP output to DVI-HDCP input?

[sjc_guy]

Hello,

This is my first post here. I'm new to the HD technologies. I just bought a 50" DLP with a DVI-HDCP connection and an LG LGDVB418 DVD player with a HDMI-HDCP connection. My question is do both connections have to be the same (ie. both should be DVI-HDCP or both should be HDMI-HDCP) for me to get the best picture? I'm currently playing my DVD's at 1080i on my LG LGDVB418 and the picture looks just the same as when I play it on my progressive scan Samsung at 480p. This is the first time I've used the technology so I don't have much to compare it to. Thanks all for any help you can provide.

[Ratman]

DVI or HDMI... both digital. Should make no difference in picture quality. Nor should an adapter to convert one to the other.

Upscaling players may not improve picture quality. The source material is still 480i.

Any improvement is soley dependant upon the player, TV and perception.

[billbillw]

DVI or HDMI... both digital. Should make no difference in picture quality. Nor should an adapter to convert one to the other.

Upscaling players may not improve picture quality. The source material is still 480i.

Any improvement is soley dependant upon the player, TV and perception.

There have been numerous reports that some STBs and DVD players that have HDMI output will change the output from studio RGB to PC RGB if you use a HDMI-DVI adapter. You will lose shadow detail if this occurs.

[mjones73]

Do you have a link to one of these reports so we can get some clarification on this? I've never heard of a difference between RGB types over a digital conenction nor does converting from HDMI to DVI do anything to change the data, it just moves some pins around...

[mceach]

Ok, Being new - I am totally confused as to what DVD player to buy. Just purchased the Panisonic PT 50DL54 which has HDMI input and a native resolution of 720p. I have the Sony 300 older 6 disk player now and has not DVI or HDMI output....nor does it have progressive scan...tell what would work best for me - doesn't matter if it only takes one disc at a time....thx and I love everything I have found on this forum...Rich

[mjones73]

Can't go wrong with the Denon DVD-1910, it's $250 on average. By the way, welcome to the forum, please just post a new post in the proper area on the forum (in this case,
DVD Players - Progressive & HiDef (720p 1080i)) instead of adding it to a post that has nothing to do with your question.

[billbillw]

Do you have a link to one of these reports so we can get some clarification on this? I've never heard of a difference between RGB types over a digital conenction nor does converting from HDMI to DVI do anything to change the data, it just moves some pins around...

It has to do with differences in output. DVI is always 8-bit RGB, but HDMI can be 8-bit RGB OR YCbCr (8,10 or 12-bit). The problem lies with conversion the process in some HDMI transmitters. See the link below
Article at Secrets (http://www.hometheaterhifi.com/volume_11_4/feature-dvi-hdmi-hdcp-connections-11-2004.html)

[mjones73]

Thanks for the info.

[57U]

I'll add that link to the FAQ on DVI Connectors.

[kdog044]

Ok, Being new - I am totally confused as to what DVD player to buy. Just purchased the Panisonic PT 50DL54 which has HDMI input and a native resolution of 720p. I have the Sony 300 older 6 disk player now and has not DVI or HDMI output....nor does it have progressive scan...tell what would work best for me - doesn't matter if it only takes one disc at a time....thx and I love everything I have found on this forum...RichGet the Panasonic S97. :rockon:

[Eddy]

billbillw

Much thanks for the reference article on HDMI vs DVI.

[crimsonfilms]

" DVD data are YCbCr, and are converted to RGB in the player for the DVI output. RGB cannot represent all the data in YCbCr, and this is why the below-black information gets truncated."

This is ABSOLUTELY INCORRECT. RGB is a much wider color range. In fact a 10 bit YCbCr will fit in a 8 bit RGB space. This is why when working with film [as in 35mm motion picture] you work in RGB and not YCrBr. Think of RGB as a cube and YCrBr as a diamond that fits in that cube.
Not to mention that many broadcast devices sample at 4:2:2 at best [DVI is full 4:4:4 sampling]

Broadcast component [be it YUV or its digital equivalent YCrBr] was designed to reduced bandwidth requirements with minimal PQ loss. It is a subtractive format.

The problem with RGB to YUV conversion [or vice versa] is the conversion is not linear. Accuracy depends on the rendering algorithm. For one or 2 passes, even a mediocre converter should be able to convert between spaces with no visual change [all though technically in the bits there will always be].

[billbillw]

" DVD data are YCbCr, and are converted to RGB in the player for the DVI output. RGB cannot represent all the data in YCbCr, and this is why the below-black information gets truncated."

This is ABSOLUTELY INCORRECT.

You should take this up with the authors over at Secrets. I'm sure that JJ and Brian would like to know if elements of their articles are incorrect.

[crimsonfilms]

I could not find an email address so I posted in their forum.

[billbillw]

I could not find an email address so I posted in their forum.

I noticed that there is a very long thread at AVSforum discussing these issues with DVI/HDMI color space. I haven't read enough of the thread to figure out exactly what the issue is though.
Here is the thread (http://www.avsforum.com/avs-vb/showthread.php?s=&threadid=486428)

Edit: I read through the thread linked above this morning. Although the thread is mainly talking about problems with upconverting DVD material, it also describes, in depth, the various ways that HDMI output can be affected when connected to a DVI input. It mentions the problems with some HDMI device choosing to use PC RGB instead of Studio RGB when connnected to DVI. This results in clipping the blacks.

[crimsonfilms]

I tried to follow the thread as much I can. There are some common mistakes there - not surprising when discussing RGB and YCrCb. I am not familiar with some of consumer devices they where talking about so I can't really follow too mcuh.

I understand the PC RGB and Studio RGB issue [basically 0-255 vs 16-235]. But this is a seperate issue regarding RGB and YCrCb in regards to dynamic range of the color sapce.

[billbillw]

I tried to follow the thread as much I can. There are some common mistakes there - not surprising when discussing RGB and YCrCb. I am not familiar with some of consumer devices they where talking about so I can't really follow too mcuh.

I understand the PC RGB and Studio RGB issue [basically 0-255 vs 16-235]. But this is a seperate issue regarding RGB and YCrCb in regards to dynamic range of the color sapce.

I understand that. Obviously, the original link that I provided had some of the facts regarding color space messed up. The main point to take out of this is that HDMI devices, whether its an STB or upscalling DVD player, can sense what they are connnected to and can change the color space output based on what it detects. It is documented that some of the devices choose the wrong color space when conncected to DVI, which can result in color push (greens mostly) or clipping of blacks.

The main thing to take of all this is that you must do some research on the device (STB or upscalling DVD) before you buy if you are going to connect with HDMI out to DVI in. It seems that most of the devices that have conversion errors are known and are being discussed on a forum somewhere. Its too bad that the manufacturers aren't more proactive in fixing these problems. They seem to think that the average consumer won't notice these problems (probably true); therefore, they shouldn't waste time fixing them.

[rudyusmc1980]

so am I right in concluding that 'DVI out to HDMI in' is OK? but 'HDMI out to DVI in' may cause problems? it may be an oversimplification, but I think that is what I need.

[TheAntMan]

They are both "all digital" cables rudy, so technically there should be no disadvantage either way, but that's technically, now for reality, many posters have had problems with the two connecting cables working properly regardless of which is the input or output. If you need a dvi/hdmi connector, I would get it and hopefully you will have no "handshake" issues between the two.

[rudyusmc1980]

the issue is black crush when going from HDMI to DVI. Handshake is another issue... since my stupid cable company will only acknowledge that the problem exists, but will not do anything to fix it...

[57U]

Most cable companies do not officially support DVI or HDMI. There are simply too many handshake issues that can be due to the firmware, the STB, the TV, the connector, etc..

If you can make the digital video connection work, fine, since the connector is enabled on most STBs, but if you can't, they won't help you, other than to tell you to use the (proven) component video connection.

I don't blame them in the least.

[Video Monster]

It is true that some dvd players incorrectly map the RGB signals. Studio and computer RGB signals are different but how much difference you will actually see is dependanton other factors as well. It is NOT true that DVI and HDMI signals are the same. DVI is capable of only 8 bit signals, while HDMI can carry 10 or even 12 bit signals. Whether or not you can see this difference is dependant on your player, display and the material being viewed.

[crimsonfilms]

The difference between Studio RGB and traditional computer RGB is the range [0-255 vs 16-235]. It is minimal in regards to displaying purposes for TV.

You are mistaken about DVI and HDMI. You numbers are correct but you are comparing apples to oranges. When HDMI refers to 10 bit or higher this in regards to YCrCb and not RGB. YCrCb is a compressed, subtractive color space. In fact 10 bit YCrCb can fit inside the entire 8 bit RGB color space.

So you are not correct.

Also, DVI and HDMI RGB signals are the same EXCEPT that there are additional protocols to carry YCrCb 444 and 422 formats at 8/10 and 12 bit. But the RGB signal IS the same.