# YCbCr over HDMI?



## William (Oct 28, 2006)

Could the 622 output YCbCr over HDMI with a firmware update? Wouldn't there be a slight improvment in PQ by using YCbCr insted of RGB?


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## William (Oct 28, 2006)

No one has an opinion or insight as to whether E* is looking at it?


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## Mark Lamutt (Mar 24, 2002)

I have no idea what YCbCr even is, so I have no insight to offer.


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## Stewart Vernon (Jan 7, 2005)

Since HDMI is supposed to be a completely digital connection... why would it ever be designed to output anything but a digital signal?

Why would you not use the Component connections if you need YCbCr?


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## Mark Lamutt (Mar 24, 2002)

Component is YPbPr, isn't it?


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## CABill (Mar 20, 2005)

About 5 months ago, there was a thread about it and DISH sent someone a reply. The thread participants seemed to be able to detect which was active. Just searching, I found:
http://www.dbstalk.com/showthread.php?p=601556#post601556
It would take an HDMI sink saying it supported YCrCb to get that sent instead of RGB. I didn't think HDMI required support of YCrCb on all sink devices. Probably better info in that thread.


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## William (Oct 28, 2006)

CABill said:


> About 5 months ago, there was a thread about it and DISH sent someone a reply. The thread participants seemed to be able to detect which was active. Just searching, I found:
> http://www.dbstalk.com/showthread.php?p=601556#post601556
> It would take an HDMI sink saying it supported YCrCb to get that sent instead of RGB. I didn't think HDMI required support of YCrCb on all sink devices. Probably better info in that thread.


HD-DVD for sure and I believe BD output YCrCb over HDMI. My HD-DVD player sends YCrCb to my VP50 scaler but the 622 sends RGB even it I set the scaler input to YCrCb.


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## wje (Mar 8, 2006)

Just to clarify what may be confusing many, I assume William isn't talking about analog over HDMI, but the digitally-encoded equivalent.

Just to confuse things more, the new HDMI spec also adds a new colorspace, which supports extended RGB (more color bits). Once TVs start using it, that should be far superior to either.


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## William (Oct 28, 2006)

wje said:


> Just to clarify what may be confusing many, I assume William isn't talking about analog over HDMI, but the digitally-encoded equivalent.
> 
> Just to confuse things more, the new HDMI spec also adds a new colorspace, which supports extended RGB (more color bits). Once TVs start using it, that should be far superior to either.


There is no such thing as analog over HDMI and HDMI is a digital only connection. Component can be a digital signal or an analog signal just like RGB can be digital or analog. It just so happens the 3 RCA analog video outputs is called component output so most people associate it with analog only. Remember that the "old" analog output on a computer is called a RGB connection even though RGB can be digital also.


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## CABill (Mar 20, 2005)

I haven't looked through that old thread again, but the reply from DISH doesn't match what other VPxx users noticed. I understand why the guy only got RGB with his DVI connection - that's all it supports. It was but a faint memory, but seemed related to what you asked originally. 

"At this time the HDMI cable outputs YCrCb at a rate of 4:2:0" sounds like it came from someone that knew something, but 4:2:0 instead of 4:2:2 or 4:4:4 (HDMI) seems odd to me. I thought 4:2:0 was more applicable to DVB than HDMI. But this isn't my area! And HDMI info isn't readily available from the org.


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## wje (Mar 8, 2006)

From a summary page (from the HDMI spec):

Pixel encodings: RGB 4:4:4, YCbCr 4:4:4; YCbCr 4:2:2

For HDMI 1.3 (called by many, HDMI 2):

Supports 30-bit, 36-bit, and 48-bit (RGB or YCbCr)


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## whatchel1 (Jan 11, 2006)

Here is a link to Wikipedia explanation of the terms YCbCr and YPbPr. 1st is digital component 2nd is analog component. 
http://en.wikipedia.org/wiki/YCrCb


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## CABill (Mar 20, 2005)

Do you have a URL for any public info, or did you fill out the info page to download the specs?

I'd thought HDMI only used 4:2:2 and 4:4:4, but really have very little to go on. I'm guessing the quoted DISH engineer's response of 4:2:0 had something more to do with DVB internals than the HDMI connector.


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## Stewart Vernon (Jan 7, 2005)

Ok... I missed that little subtlety... I had been working under (apparently false) an assumption that all HDMI digital video was created equal... but it appears from this thread that there are different flavors of digital video from an HDMI connection?

No wonder I was confused... I couldn't understand why there would be more than one type of connection from an HDMI, as I thought it was supposed to be a digital video standard connection.

Now I understand the original poster's question better.... but am more confused about HDMI, in that I don't understand why all HDMI isn't created equal. Seems like that would have perhaps cut down on some of the compatibility glitches?


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## whatchel1 (Jan 11, 2006)

The reason is the standard for HDMI is still a work in progress. the 1.3 that they are trying to implement still isn't working correctly. They have not been able to get the DRM crap to work at all. the studios are still pushing to make it illegal for us to get HD onto another source for our own use.


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## dave1234 (Oct 9, 2005)

The output of the 622 HDMI is YCbCr. All the SPMTE HD standards call out YCbCr color space. That isn't to say some displays can accept either RGB or YCbCr, but the HD spec. is YCbCr.
The 4:4:4 vs 4:2:0 or 4:2:2 is only related to color space in that the 4:4 or 4:2 relates to the sample rate for Luma(Y) and Chroma(C). I like to think of the difference between 4:2:0 and 4:2:2 as the vertical chroma sample rate.

To quote from the link at the end:

So where does 4:2:0 (PAL DV, DVD, main-profile MPEG-2) fit in? 4 x Y, 2 x Cr, and 0 x Cb? Fortunately not! 4:2:0 is the non-intuitive notation for half-luma-rate sampling of color in both the horizontal and vertical dimensions.

http://www.adamwilt.com/DV-FAQ-tech.html#colorSampling


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## William (Oct 28, 2006)

dave1234 said:


> The output of the 622 HDMI is YCbCr. All the SPMTE HD standards call out YCbCr color space. That isn't to say some displays can accept either RGB or YCbCr, but the HD spec. is YCbCr...


My 622 is outputting RGB. When I first had it installed my VP50 input was set to YCbCr (used my HD-DVD input which is YCbCr 4:2:2) and the colors were off. I had to change the input to RGB for it to display correctly. How do I change my 622from RGB to the correct YCbCr output?


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## dave1234 (Oct 9, 2005)

William said:


> My 622 is outputting RGB. When I first had it installed my VP50 input was set to YCbCr (used my HD-DVD input which is YCbCr 4:2:2) and the colors were off. I had to change the input to RGB for it to display correctly. How do I change my 622from RGB to the correct YCbCr output?


William,
I can't explain your situation. I'm feeding my RCA 61" DLP with a HDMI to DVI connector. My TV only accepts YCbCr. Maybe the DVI vs HDMI input has something to do with the issue, but that's not clear. Are you able to connect the 622 directly to your display? Does that work any differently?

The 622 would have to convert the color space from YCbCr to RGB, something I think is undesirable, but not as bad as a format conversion.


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## William (Oct 28, 2006)

dave1234 said:


> William,
> I can't explain your situation. I'm feeding my RCA 61" DLP with a HDMI to DVI connector. My TV only accepts YCbCr. Maybe the DVI vs HDMI input has something to do with the issue, but that's not clear. Are you able to connect the 622 directly to your display? Does that work any differently?
> 
> The 622 would have to convert the color space from YCbCr to RGB, something I think is undesirable, but not as bad as a format conversion.


I have a HD-10K projector which has no internal processor and only accepts a native 1080p signal, so I can't hook the 622 directly to it. I will unplug the 622 and try switching the VP-50's input to YCbCr and see if this forces it to output YCbCr (although this did not work on the initial setup).


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## dave1234 (Oct 9, 2005)

William said:


> I have a HD-10K projector which has no internal processor and only accepts a native 1080p signal, so I can't hook the 622 directly to it. I will unplug the 622 and try switching the VP-50's input to YCbCr and see if this forces it to output YCbCr (although this did not work on the initial setup).


William,
Time for me to eat some crow.  I forgot DVI is RGB only, it does not support YCbCr. Therefore my display only supports RGB on the DVI input. Therefore the 622's HDMI output is RGB. HMDI can support RGB or YCbCr unlike DVI. I wouldn't be concerned about the color space conversion as that conversion can be an exact process, unlike format conversion.

I don't know if Dish plans on adding the ability to support YCbCr output. It's probably not a high priority as the affects on quality should be next to zero.


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