# Is the 622's HDMI output RGB or YCbCr?



## ssj2 (Dec 1, 2004)

Does anybody know if the HDMI output is RGB or YCbCr? If RGB, is the 622 sending proper studio levels of 16 - 235, or PC levels of 0 - 255? I asked Dish Tech Support but they were of no help. Thanks


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## keenan (Feb 8, 2005)

My VP30 reports a RGB signal at the Dish input.


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## mraroid (Jun 11, 2006)

ssj2 said:


> Does anybody know if the HDMI output is RGB or YCbCr? If RGB, is the 622 sending proper studio levels of 16 - 235, or PC levels of 0 - 255? I asked Dish Tech Support but they were of no help. Thanks


This is a very good question. If you ever figure out the answer, will you post it here please?

Thank you.

Mr. Aroid


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## olgeezer (Dec 5, 2003)

Neither. RGB and Component outs are analog sources. HMDI passes the digital bitstream to the display. This article may help from ecoustics:

http://forum.ecoustics.com/bbs/messages/34579/122868.html


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## SaltiDawg (Aug 30, 2004)

olgeezer said:


> Neither. RGB and Component outs are analog sources. HMDI passes the digital bitstream to the display.


The question is, in fact, valid.


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## ssj2 (Dec 1, 2004)

Keenan, thanks for your response.

Olgeezer, digital RGB and YCbCr are supported by HDMI -- they are the bitstream.

Here's a quote from the official HDMI website's FAQ about the HDMI specs: "Ability for PC sources to use their native RGB color-space while retaining the option to support the YCbCr CE color-space." Here's the link: http://www.hdmi.org/about/faq.asp#hdmi_specification


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## dino622 (Jun 19, 2006)

I would have to guess that it is YCbCr, since that is the way MPEG is stored, and that is what analog component input would get converted to when sampled.


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## ssj2 (Dec 1, 2004)

dino622, that would have been my guess as well. However, keenan's reports that his iScan recognizes it as RGB.


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## DonLandis (Dec 17, 2003)

As I recall the color space for analog video RGBHV is about 83% of that of pure digital video. (per CCIR601 specifications) While DVI /HDMI may support analog converted color space equal to RGBHV the highest form of analog video, a pure DVI and/ or all digital processed program will lose some color space when that signal is downconverted to analog. Therefore for the highest quality, maintain all the color space from the original DVI / HDMI all the way with no analog conversions anywhere in the process. 
Using non tech speak the RGBHV analog video will have slightly less color saturation than a DVI image assuming that DVI image was maintained digital from the camera. Component Y, Pr, Pb, has the same color space as RGBHV but will suffer some sync artifacting as a result of the encoding of the YUV algorhythm. This is usually only detected by the highest quality monitors, however.


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## dude2 (May 28, 2006)

Does a tv screen put out its picture from analog information or digital. If it needs analog information will we really ever see all the pq?
I just read an article that to have true HD your screen needs to have 2megapixels of information and this article said that at present plasma can not do that but crt, and lcd can.
All the info and who speaks without a forked tongue?


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## DonLandis (Dec 17, 2003)

_"Does a tv screen put out its picture from analog information or digital."_

A matter of interpretation- The image is all about light which really is analog. In an all digital mobnitor such as an LCD screen the light is triggered by a dispaly that comes on via a digital signal on or off per each pixel. In an analog display, the light comes on with phosphors that light up or glow to peak brightness and then decay in brightness over time (persistence of the phosphor) This is what allows the interlace scan to work as the first field is bright and decaying as the second interlace field replaces it.

The "PQ" of an HD image is dependent on a huge number of factors that have limits at each step of the way. One thing is certain, you can't generate image detail (resolution) where none existed at that step. All you can do is optimize each step so as to not lose detail either by bandwidth limitations or electrical noise. Having an all digital signal path to the image on your monitor will eliminate the noise and making sure your monitor has enough pixels that the image has will insure you get all the image that the signal has when it arrives.

_"I just read an article that to have true HD your screen needs to have 2megapixels of information and this article said that at present plasma can not do that but crt, and lcd can."_
I'm not sure what the latest specs are for Plasma but last I chedcked the statement was true. Plasma is limited (state of the art) to less than LCD and DLP for pixel resolution. Today, you CAN buy 1080 x 1920 digital monitors but I don't believe yet in Plasma screens. CRT can be made to display 1080 x 1920 but only under laboratory conditions. Typically, CRT's are run at such brightness levels that they can only reproduce at best, 1100 x 1200 lines. Note there is no such thing as "pixels" in an analog (CRT) monitor. But in addition to resolution, analog monitors are incapable of reproducing the color space that digital can do. CRT's will present chroma distortion when pushed to saturation levels that digital monitors can achieve. eg a yellow will top out on a CRT fed with a digital signal converted to analog at 224 bits while the all digital monitor will resolve image differences in the range of 224 to 254 bits of data. Each color has it's range and is expressed by a complex wave graph. Ref CCIR 601. But in all cases, analog display is not as color space capable as is digital.

_"All the info and who speaks without a forked tongue?"_

Good question. Part of the problem is that to really understand this stuff, it does take some higher education in digital electronics, image science, and television production through presentation process. Not an easy task for one person. Approach the subject with the understanding that you can achieve progressively better results as you go from 1 thru 5 as follows:

Consumer Video formats:
1. Composite CVBS signal (analog)
2. Y/C or SVHS signal (analog)
3. Component Y, Pr, Pb (analog)
4. RGBHV, RGB (w embedded sync) (analog)
5. DVI / HDMI (digital)

If you are not seeing a progressive improvement in image quality then either your monitor is not high enough quality or the signal processor is not working properly. This would speak to the complaints many have that with their system component looks better than DVI. Technically it shouldn't unless something is not working properly.


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## ssj2 (Dec 1, 2004)

DVI/HDMI are not video formats, they are transmission methods.

DVI can carry analog & digital RGB (DVI-I) or digital RGB (DVI-D).

HDMI can carry digital RGB or digital component (YCbCr).


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## ctshead (Jan 3, 2006)

ssj2 said:


> DVI/HDMI are not video formats, they are transmission methods.
> 
> HDMI can carry digital RGB or digital component (YCbCr).


Thats correct.

And, SD transmissions are coded using SMPTE 170m color space, and HD transmissions are coded using ITU-R BT.709-4 color space.

HDMI video transfers only as RGB4:4:4 or YCbCr4:4:4 or YCbCr4:2:2
It accomodates all the ATSC/DVB/VGA pixel timings. All HDMI devices must accept RGB but dont have to accept YCbCr.


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## DonLandis (Dec 17, 2003)

ssj2- semantics- transmission format or transmission method the interconnect used will limit the capability of the signal. in the case of DVI / HDMI carrying analog video, that is true but the way it does that is by a piggyback of additional wires within the DVI-I cable. I've always felt the correct description should have been DVI+A if semantics is your pet peeve. The digital portion of the cable reduces the video noise in the RGB signal. Additionally it maintains the pure on -off digital switching to produce the best image while all analog suffers circuit rise and fall time in the analog signal. Again my list is a simple way to choose the method of display for the best image with least artifacts caused by the format or transmission. If you disagree with the order then we can get to the technical details.


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## dave1234 (Oct 9, 2005)

ALL the HD standards for 1080i, 720p etc. are specified as YCbCr. Computer display interfaces are normally RGB.


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## ssj2 (Dec 1, 2004)

Don, I agree with what you're saying. I clarified the transmission method v. transmission format because your list is labeled "Consumer Video Formats". As evidenced by Olgeezer's post here (and numerous posters elsewhere) many people believe "digital is digital".

Back to the topic of the thread I started. Keenan posted his iScan recognized the HDMI output of the 622 as RGB. I decided to test this against settings from my Panasonic S97 DVD player by switching its HDMI output to RGB and activating the player's studio and enhanced settings.

edited. See below.


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## DonLandis (Dec 17, 2003)

ssj2- Based on what you observed, I would tend to agree with your assessment. As I recall the basics the DVI connection has 4 lines Data R, Data G, and Data B, plus clock. This can be replicated for broader bandwidth. I just don't recall all the details and don't have time to look them up right now. What I was concerend with is that some may confuse this data RGB signal line with the analog line that piggybacks on the one end of the DVI-I. I use this in my 921 to connect to an RGBHV breakout cable for connection and yes, I have to pump up the levels to calibrate properly as compared with the same PJ and 921 connected with DVI. Not having lots of equipment to compare, I thought this was just the way my projector worked. 
I have a 622 here but waiting for the delayed installer since I am concerned with messing with leased equipment where install is part of their warranty per CSR. At this point I plan to connect the 622 with component since the wide reports of HDMI failure on this box. I have two switchable DVI inputs on my PJ and they are occupied now with the TIVO and the upconverting DVD player. I may run tests on the 622 / HDMI to DVI later after the installer leaves but the image will need to improve greatly and the 622 trouble free before I pull the DVI from the TIVO. This is about my entertainment, not experimenting or being Dish's lab rat. 
I'll settle back now and just follow the threads to see where all this leads.


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## ssj2 (Dec 1, 2004)

OK, realizing a user error with the DVD player's settings I re-did my test. With the DVD player's RGB output set to standard (studio levels) and my projector's input set to standard, my calibrated brightness & contrast settings (AVIA for DVD & HDNET test patterns for HD) matched exactly with the 622's output. 

Therefore, it would appear the 622 is maintaining studio RGB levels from its HDMI output.


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## ssj2 (Dec 1, 2004)

I just received this emai response from Dish Network tech support:

"Thank you for your e-mail. At this time the HDMI cable outputs YCrCb at a rate of 4:2:0. I Hope this helped if you have any further questions, please let me know if you need anything else."

Given that the YCrCb signal should be sent at studio levels it would make sense that brightness and contrast settings using the 622 matched the RGB studio settings from the DVD player. Odd that Keenan's iScan recognized the signal as RGB.


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## keenan (Feb 8, 2005)

It may be a setting on the VP30 that's forcing it to see RGB at the input, I don't know why it would do that though...I'll look around in the VP30 menus tomorrow...or tonight, Friday-06/24.


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## dave1234 (Oct 9, 2005)

keenan said:


> It may be a setting on the VP30 that's forcing it to see RGB at the input, I don't know why it would do that though...I'll look around in the VP30 menus tomorrow...or tonight, Friday-06/24.


 I don't see a way any monitor can determine whether a signal is RGB or YCbCr. There is no information in the data stream to indicate which color space is being used.

That said all HD signals are YCbCr unless a conversion has been done in a receiver somewhere.


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## ssj2 (Dec 1, 2004)

The monitor can and does recognize whether a signal is RGB or YCbCr. If YCbCr is detected the display will use SD 601 or HD 709 decoding to transform the signal into RGB. Here's a great post on the subject: http://www.avsforum.com/avs-vb/showthread.php?p=6330772&&#post6330772


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## Bradtothebone (Aug 11, 2003)

ssj2 said:


> The monitor can and does recognize whether a signal is RGB or YCbCr. If YCbCr is detected the display will use SD 601 or HD 709 decoding to transform the signal into RGB. Here's a great post on the subject: http://www.avsforum.com/avs-vb/showthread.php?p=6330772&&#post6330772


That's a great read. Thanks, ssj2!

Brad


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## DonLandis (Dec 17, 2003)

ditto! I've always enjoyed reading stuff by wiggles/Kuo and even Joe Kane. One thing that I felt was missed on the BTB topic was that while the voltages in a calibrated monitor should not be visible on BTB, the whole origin of BTB content was to facilitate luminance keying in analog systems. In the case of a keyer, and a camera used to shoot luminance keys, the BTB is seen (detected) by the electronics and not the human eye from the BVM once calibrated properly. Use of the BTB toeroom for content that extends into that region, tells me that whoever justifies this really did not calibrate his monitor with PLUGE as claimed. In a good production, no image should have content below 7.5IRE to translate to less than 16 bits on digital conversion.


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## keenan (Feb 8, 2005)

keenan said:


> It may be a setting on the VP30 that's forcing it to see RGB at the input, I don't know why it would do that though...I'll look around in the VP30 menus tomorrow...or tonight, Friday-06/24.


Okay, I hooked up a set of component cables as well as HDMI from the 622 to the VP30.

At the component input the VP30 it detects a YPbPr signal.

At the HDMI input the VP30 detects a RGB signal.


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## Jim Noyd (May 15, 2005)

keenan said:


> Okay, I hooked up a set of component cables as well as HDMI from the 622 to the VP30.
> 
> At the component input the VP30 it detects a YPbPr signal.
> 
> At the HDMI input the VP30 detects a RGB signal.


Correct the 622's hdmi output is digital RGB


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## ssj2 (Dec 1, 2004)

Jim Noyd said:


> Correct the 622's hdmi output is digital RGB


Jim, how do you come across this information? I know Keenan's experience is with his iScan. I'm just trying to get a bit of background before discarding the response I received from Dish Network. Thanks.


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## Jim Noyd (May 15, 2005)

Because I have the 622's hdmi hooked up successfully to my projector's DVI input with an adapter, and that is what the PJ accepts.


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