[RGB vs YCbCr] Where is the best place to do the color conversion? Player or Display? - AVS Forum

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HDTV Software Media Discussion

Tony_Montana's Avatar Tony_Montana
06:33 PM Liked: 15
post #1 of 6
07-01-2011 | Posts: 382
Joined: Mar 2011
You may find my questions totally noob, but i would like to make clear theory about color conversions.
i didnt found a sub-forum for general theory about displays or bluray players so i post it here. Moderators can always move it anywhere.

All the people in HTPC`s area talk about the new madVR - video renderer and the noticable improve of Picture Quality.
According to the developer there is no way to upsample the color on a pc without converting this to RGB first. Its impossible the card to output untouched YCbCr data,
so he suggests to set our htpc cards' pixel format to rgb and our display`s input source also to rgb.
With this project we skip one color conversion setting it up fullRGB 4:4:4 all the way. The only conversion that happens this way is the 4:2:0 to RGB.

But what happens with our standalone bluray players? Does anybody know if consumer electronics when uplsampling 4:2:0 to 4:2:2 or YCbCr 4:4:4 also convert the color first to rgb and then to YCbCr?
If we assume that we have a perfect bluray player like oppo93 and a display capable to handle both RGB/YCbCr which color format we would choose?
YCbCr 4:4:4 or RGB?

Where is the best place to do the color conversion?
option 1:
4:2:0 to 4:4:4 in the player ---> 4:4:4 to RGB on the display (two color conversions)
or option 2:
4:2:0 to rgb in the player ---> no color conversion on the display (one color conversion)
Smackrabbit's Avatar Smackrabbit
09:17 PM Liked: 32
post #2 of 6
07-01-2011 | Posts: 895
Joined: Sep 2001
This is really display and device dependent. Some receivers or processors only handle certain color spaces correctly, and might lose data on others. Some displays might also only handle a certain color space, like YCbCr 4:4:4, correctly and have issues on YCbCr 4:2:2 and RGB. Really the only way to determine this is with some test patterns (the Spears and Munsil Blu-ray works well) and testing the various colorspaces on your display with a player that can output all of them correctly (such as an Oppo).

I can say for certain that a device that only outputs RGB is not going to be ideal for 100% of people, as I've seen too many devices and displays that need a specific colorspace to work correctly. Unless you are sending this output to a video processor that converts it to the correct signal format for your display, there is a good chance of an issue.
Tony_Montana's Avatar Tony_Montana
04:52 AM Liked: 15
post #3 of 6
07-02-2011 | Posts: 382
Joined: Mar 2011
chris i am very happy that you repplied my post.
i have to say that all these color conversions concerns started when i read your article:
Secrets bluray player HDMI benchmark.

I think that although displays are rgb native, most of them are more capable to handle YCbCr than RGb.

It would be also very interesting if we could ever success in a pc the same results in the YCbCr 4:2:0 --> RGB conversion like oppo does.
Do you also think that this will be GPu`s hardware dependent?
I think this is the most objective comparison between htpcs and standalone blu-ray players.
I am not oppo fan boy, but there is no clear answer about this issues all over the internet.
HTPCs have only one way to make the color conversions right and not all displays can do it this way.
PooperScooper's Avatar PooperScooper
06:57 AM Liked: 525
post #4 of 6
07-02-2011 | Posts: 20,028
Joined: Dec 2002
In this thread, in various places, there's discussion on how to determine the proper color space to send to your display: http://www.avsforum.com/avs-vb/showthread.php?t=1131344

Also, on Stacey and Don's website there are white papers that go into more detail.

Tony_Montana's Avatar Tony_Montana
08:40 AM Liked: 15
post #5 of 6
07-02-2011 | Posts: 382
Joined: Mar 2011
larry i think you cannot have accurate results using this kind of method.
you can use it in a standalone bluray player but not in a htpc.
you can calculate the YCbCr-->RGB that is in your display (if your card supports YCbCr)
but not the first initial color conversion of 4:2:0-->YCbCr because every software has to do it RGb first.
Every pc software needs to do this conversion first.
If i am wrong please forgive me ArcSoft & Cyberlink developers.
GPUs also cannot output untouched YCbCr data.
That is my main concern.
ChrisW6ATV's Avatar ChrisW6ATV
05:25 PM Liked: 17
post #6 of 6
07-05-2011 | Posts: 4,207
Joined: Nov 2000
Since every display ultimately outputs RGB and nothing but RGB (except those four-color Sharp ones), you would think an RGB input (whether analog or digital) would be the least likely to have problems within any display device. It surprises me that some displays might not be designed that way.
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