YCbCr color coding

saintfrenz · 01-17-2018, 11:44 AM

Hello,

I have a Samsung MU6300 4K TV connected to my laptop via the Vantec USB 3.0 To HDMI 4K Display Adapter which uses the DL-5500 chipset. I have two problems:
1. The desktop looks awful with the colors all washed out. Is there any way to set the color coding to YCbCr (instead of RGB which I think is what is being used currently)?
2. Video played on my laptop (VLC, MPC) etc have horrible stutter and tearing. Any settings I need to do to fix that?

Thanks.

AlbanRampon · 01-18-2018, 09:13 AM

Hello,

That adapter does NOT do ANY colour correction today. This means it displays what it gets. I advise you change the TV settings so colours are displayed properly. Other settings on the adapter were decided by the manufacturer and are not changeable.

For the video, try Film and TV which runs with GPU acceleration. For my Intel i7 Surface Pro 3 on Windows 10, a 4Kp60 video decoding is awful on the native display with VLC and all smooth with Microsoft Film and TV.

Regards,
Alban

qp6019352 · 01-20-2018, 11:49 AM

Quote:

Originally Posted by saintfrenz

1. The desktop looks awful with the colors all washed out. Is there any way to set the color coding to YCbCr (instead of RGB which I think is what is being used currently)?

There are two kinds of RGB:

1. RGB Full Range (0-255)
2. RGB Limited Range (16-235)

It sounds like your DisplayLink adapter outputs RGB Limited Range, whereas your TV expects to receive RGB Full Range, which makes black look more like gray and makes everything look washed out (the other way around it would clip black detail and make colors look crushed).

Just tell your TV that it receives RGB Limited Range. Most TVs allow to do this.

On Samsung TVs, the option is usually called "HDMI Black Level", which can be set to "Low" or "Normal".

Also:

Quote:

Originally Posted by AlbanRampon

That adapter does NOT do ANY colour correction today. This means it displays what it gets. I advise you change the TV settings so colours are displayed properly. Other settings on the adapter were decided by the manufacturer and are not changeable.

If AlbanRampon is correct in what he says and your DisplayLink adapter indeed is outputting Limited Range RGB, then it is probably caused by the graphics driver of the PC.

The Intel graphics driver allows to adjust it as well, it's explained over there for example:

http://www.avsforum.com/forum/26-hom...l-0-255-a.html

That being said: I wonder if the graphics driver really could influence what kind or RGB range the DisplayLink adapter is outputting at.

Maybe AlbanRampon can shed some light on this.

qp6019352 · 01-24-2018, 10:29 AM

Quote:

Originally Posted by qp6019352

If AlbanRampon is correct in what he says and your DisplayLink adapter indeed is outputting Limited Range RGB, then it is probably caused by the graphics driver of the PC.

The Intel graphics driver allows to adjust it as well, it's explained over there for example:

http://www.avsforum.com/forum/26-hom...l-0-255-a.html

That being said: I wonder if the graphics driver really could influence what kind or RGB range the DisplayLink adapter is outputting at.

Maybe AlbanRampon can shed some light on this.

Any update?

AlbanRampon · 01-25-2018, 01:24 PM

Hello,

From me, no update: we still don't do any transformation.
We get a 0, we give a 0. We get a 16, we will give a 16.

As you indicated, the TV has probably a setting not matching the one from the graphics card, where pixels are being computed, or other elements in between.
The fact that nobody else reported the issue does tend to confirm this is a local issue as the chip has been shipped in millions units and has been on the market for years...

Kind regards,
Alban

qp6019352 · 01-26-2018, 11:36 AM

I do not have seen this on DisplayLink either, was just curious.

saintfrenz · 01-27-2018, 02:30 PM

Yes, the Intel Graphics Control Panel does allow a choice in color space for output between RGB and YCbCr, and also between Full/Limited range for RGB,
but only if the display is connected to it directly (i.e. though the HDMI on the laptop itself).
When connected through an adapter, I cannot even see the display in the Intel Graphics Control Panel (as expected)
Even when connected directly, the color looks bad when set to RGB (irrespective of Full/Limited) and looks good when set to YCbCr.
However, my laptop has the Intel HD4000 whose pixel clock caps out at 225MHz which means it can only push 4K @ 24Hz.
That's fine for 24p video rendering but awful for desktop use with anything even as simple as a mouse movement being jittery. Hence the whole need for an adapter.

With the Vantec adapter (DL-5500), I tried video playback with hardware acceleration enabled (DXVA with LAV Decoder on Media Player Classic) but was still stuttering a lot. The TV does not have any options for changing RGB range anywhere as far as I could see.

I returned the Vantec adapter (without any more extensive testing) and got a Plugable adapter that has the newer DL-6950 chipset since I was only getting 30Hz with the DL-5500 anyway and the DL-6950 is capable of 4K @ 60Hz.

A note about the TV - every time a new device connects to it and/or connection parameters change (like refresh rate in the monitor settings or the color space in the Intel Graphics Control Panel when connected directly or the HDMI UHD color setting on TV etc)
the TV goes through a "detection" and sets the appropriate mode (one of Cable Box, Blu-ray player, Game Console, PC and Home Theatre System). "PC" mode is the only one in which you get no chroma subsampling i.e. 4:4:4 chroma. Detailed review/settings on this TV is here

https://www.rtings.com/tv/reviews/samsung/mu6300

Results with the new adapter:
1. The video playback issue is now resolved. As a bonus, I also get HDMI bitstreaming with audio. I don't know whether HDMI audio bitstreaming was possible with the Vantec adapter.
2. The color first came just as bad as the first adapter. After setting the HDMI Black Level to "Normal" (as opposed to "Low" before) and flipping HDMI UHD color off and on, it went through the "detection" again and came back with correct color. I had not tried this with the first adapter.

In short, everything is good now. I think there might be some HDMI color space/settings related "negotiation" going on when the TV connects to a device and goes though the "detection" but without further research into the TV and HDMI spec, I can't say.

P.S. from @qp6019352 description, it looked like color crush and not washed out.

01-17-2018, 11:44 AM	#1
saintfrenz Junior Member Join Date: Jan 2018 Posts: 3	YCbCr color coding Hello, I have a Samsung MU6300 4K TV connected to my laptop via the Vantec USB 3.0 To HDMI 4K Display Adapter which uses the DL-5500 chipset. I have two problems: 1. The desktop looks awful with the colors all washed out. Is there any way to set the color coding to YCbCr (instead of RGB which I think is what is being used currently)? 2. Video played on my laptop (VLC, MPC) etc have horrible stutter and tearing. Any settings I need to do to fix that? Thanks.

01-18-2018, 09:13 AM	#2
AlbanRampon Senior Member Join Date: Sep 2015 Posts: 1,685	Hello, That adapter does NOT do ANY colour correction today. This means it displays what it gets. I advise you change the TV settings so colours are displayed properly. Other settings on the adapter were decided by the manufacturer and are not changeable. For the video, try Film and TV which runs with GPU acceleration. For my Intel i7 Surface Pro 3 on Windows 10, a 4Kp60 video decoding is awful on the native display with VLC and all smooth with Microsoft Film and TV. Regards, Alban __________________ Alban Rampon Senior product manager, universal docking stations and accessories Where to download the latest DisplayLink drivers How to clean up a corrupted installation How to report issues to DisplayLink for a speedy resolution

01-25-2018, 01:24 PM	#5
AlbanRampon Senior Member Join Date: Sep 2015 Posts: 1,685	Hello, From me, no update: we still don't do any transformation. We get a 0, we give a 0. We get a 16, we will give a 16. As you indicated, the TV has probably a setting not matching the one from the graphics card, where pixels are being computed, or other elements in between. The fact that nobody else reported the issue does tend to confirm this is a local issue as the chip has been shipped in millions units and has been on the market for years... Kind regards, Alban __________________ Alban Rampon Senior product manager, universal docking stations and accessories Where to download the latest DisplayLink drivers How to clean up a corrupted installation How to report issues to DisplayLink for a speedy resolution

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01-26-2018, 11:36 AM	#6
qp6019352 Member Join Date: Dec 2016 Posts: 39	I do not have seen this on DisplayLink either, was just curious.

01-27-2018, 02:30 PM	#7
saintfrenz Junior Member Join Date: Jan 2018 Posts: 3	Yes, the Intel Graphics Control Panel does allow a choice in color space for output between RGB and YCbCr, and also between Full/Limited range for RGB, but only if the display is connected to it directly (i.e. though the HDMI on the laptop itself). When connected through an adapter, I cannot even see the display in the Intel Graphics Control Panel (as expected) Even when connected directly, the color looks bad when set to RGB (irrespective of Full/Limited) and looks good when set to YCbCr. However, my laptop has the Intel HD4000 whose pixel clock caps out at 225MHz which means it can only push 4K @ 24Hz. That's fine for 24p video rendering but awful for desktop use with anything even as simple as a mouse movement being jittery. Hence the whole need for an adapter. With the Vantec adapter (DL-5500), I tried video playback with hardware acceleration enabled (DXVA with LAV Decoder on Media Player Classic) but was still stuttering a lot. The TV does not have any options for changing RGB range anywhere as far as I could see. I returned the Vantec adapter (without any more extensive testing) and got a Plugable adapter that has the newer DL-6950 chipset since I was only getting 30Hz with the DL-5500 anyway and the DL-6950 is capable of 4K @ 60Hz. A note about the TV - every time a new device connects to it and/or connection parameters change (like refresh rate in the monitor settings or the color space in the Intel Graphics Control Panel when connected directly or the HDMI UHD color setting on TV etc) the TV goes through a "detection" and sets the appropriate mode (one of Cable Box, Blu-ray player, Game Console, PC and Home Theatre System). "PC" mode is the only one in which you get no chroma subsampling i.e. 4:4:4 chroma. Detailed review/settings on this TV is here https://www.rtings.com/tv/reviews/samsung/mu6300 Results with the new adapter: 1. The video playback issue is now resolved. As a bonus, I also get HDMI bitstreaming with audio. I don't know whether HDMI audio bitstreaming was possible with the Vantec adapter. 2. The color first came just as bad as the first adapter. After setting the HDMI Black Level to "Normal" (as opposed to "Low" before) and flipping HDMI UHD color off and on, it went through the "detection" again and came back with correct color. I had not tried this with the first adapter. In short, everything is good now. I think there might be some HDMI color space/settings related "negotiation" going on when the TV connects to a device and goes though the "detection" but without further research into the TV and HDMI spec, I can't say. P.S. from @qp6019352 description, it looked like color crush and not washed out.