Direct Display Profiling

Using the in-built LightSpace CMS patch generator is one of the easiest way to perform accurate display calibration, and negates the need for separate signal generator hardware.

The following instructions explain the best approach to using direct HDMI connections for profiling, as well as the included Calibration Client Java App to enable profiling of display connected to any additional PC/Mac/Linux system.


Calibration Client

LightSpace Direct Profiling

When LightSpace CMS is installed a sperate Java Application (called 'Calibration Client') is installed along with the main software, and can be seen within the main 'Programs' menu.

This application can be copied and loaded into any other system (PC/Mac/Linux) running Java to enable calibration of displays over a facility wide network.

This means that with LightSpace CMS running on PC, with probe attached, the patches can be displayed on any display connected to any other PC/Mac/Linux system on the same network.

In the above diagram LightSpace CMS is running on the laptop, with the Java App running on the Mac, connected to the LightSpace laptop via Ethernet. When LightSpace generates a patch colour the same colour is replicated on the Mac via the Java App, and the probe records the measured value and sends it to LightSpace CMS.

Calibration Client Java App

The Calibration Client can be seen in the 'Installed programs' list within the LightSpace PC. To copy it to any other PC/Mac/Linux system simply navigate to the LightSpace CMS installation folder and copy the 'CalibrationClient.jar' from within the 'Calibration Client' folder, if installing on a MAc or Linux system.

If installing on another Windows PC system it is easier to install the Free DPS version of LightSpace, and access the Calibration Client from the install program link.

Using the Java App, any display connected to any PC/Mac/Linux system can be directly profiled from the LightSpace laptop with no additional hardware, using the 'Network Manager' to connect over an Ethernet network to the Calibration Client Java application. For more information see the Network Interface section of the LightSpace CMS Profiling User Manual.

LightSpace Connect Network

PatchSize

The PatchSize controls within the LightSpace Network Manager can be used to set any specific patch size and position for display profiling.

The values are normalised 0-1 values, represented in percentage terms, with the 'xy' boxes setting the position of the Top Left corner of the patch window, and the 'WH' boxes setting the Width and Height of the patch window, again in normalised percentage terms.

Using these percentage terms it is a simple process to calculate the required values for any given patch size and position, be it a percentage of screen width/height, or screen area.

As screen area is the common requirement for setting patch size (and as screen width/height is a very simple procedure), the following explains how to calculate the values for screen area patch size/position.

  • The dimensions of the patch are normalised 0-1, but represented as a percentage
  • Therefore, the area of the whole screen is 1x1=1 (where 1=100%)
  • If 10% is the required patch size, the normalised area of the patch required is 0.1 (0.1 is 10% of 1)
  • The square root of 0.1 is 0.3162, which gives the Width and height normalised values for the patch size
  • This normalised value needs to converted into a percentage (31.625) and rounded up gives 32%
  • Therefore the 'WH' values for a 10% patch window are 32,32

The 'xy' values to centralise the patch window can now be calculated by simply subtracting half the patch size from half the screen size.

  • Half screen size is 50%, so deducting 50% of 32% is 50-16=34, giving 34%
  • Therefore the 'xy' values for a centralised 10% patch are 34,43

Therefore the final figures to be entered into the Network Manager are: 34,34,32,32.

Using the above, a centralised 12% patch window would be 33,33,35,35, and a 22% patch window 27,27,47,47.

madTPG - Test Patch Generator
madTPG Calibration

Yet another option for remote network based calibration is to use the Test Patch Generator built in to madVR, which is a free Home Cinema player and can be download from madvr.com.

When installed, madVR installs a separate executable program called madTPG.exe, which can be run as a standalone Test Patch Generator, and controlled directly via LightSpace CMS.

For operational information see the madVR User Guide page.


Screen Mirroring
Miracast Profiling

One further option that can be used on modern home TVs is to use Miracast to mirror you PC desktop directly on your TV. If your TV doesn't have Miracast built-in an adaptor can be used.

Note: The one potential issue with a direct wifi connection is that it bypasses the hardware HDMI input on the TV, and may not be a faithful representation of the TV's response to signals via the HDMI port. But, it is very simple to verify this by comparing to a direct HDMI connection from the LightSpace CMS PC.

HDR-10 Calibration

HDR Meta-Data

PQ based HDR displays use meta-data within the signal to trigger the display's HDR capabilities. So, if the HDR display to be calibrated cannot be set to HDR mode manually a method for meta-data insertion into the HDMI signal path is required.

The HDfury Integral4K60 can be added to the HDMI signal path from the LightSpace CMS laptop to the HDR UHDTV, injecting the required meta-data.

If the HDR display can be set manually to HDR mode no meta-data within the HDMI stream will be required.

Direct HDMI Profiling

Direct HDMI

There is a lot of confusion regarding the direct use of a PC's HDMI output as a patch generator, mainly related to historic issues with old graphics cards and chip-sets.

The reality is that modern graphics cards and chip-sets have very accurate output signals, and can be used for extremely accurate patch generation and hence display profiling and calibration, if the VCGT is correctly nullified using SpaceMatch DCM.
(Note: the standard Windows API/reset call for the VCGT doesn't generate a true Null setting, as explained within the SpaceMatch DCM page.

A direct HDMI connection from the LightSpace CMS PC can therefore be the one of the best options for accurate display profiling, with the VCGT issue managed correctly.


PC Configuration

When using direct HDMI (or DVI/DisplayPort) output for patch generation there are a number of primary considerations that must be kept in mind.

ICC Profiles
A major potential issue with HDMI output is the use of ICC profile within the PC for internal calibration. Such ICC profiles will distort the HDMI output, making any attempt to use the output signal for profiling and calibration totally inaccurate.

Graphics Card Settings
As with ICC profiles, any inaccurate set-up of the graphics card settings will also distort the output HDMI signal.

EDID / DDC-CI / MCCS
Extended display identification data (EDID) is a data structure provided by displays to describe their capabilities to a graphics card. It is this that enables the graphics card to know the correct signal information to send to the display.

DDC-CI stands for Display Data Channel Command Interface, and is a collection of protocols for communication between a display and a graphics card that enable the PC to adjust display parameters, such as brightness and contrast.

Monitor Command Control Set, or MCCS, defines the protocol for controlling the properties of a display from a PC, or set-top box, etc., often using DDC-CI for communication.


PC Desktop Set-up

To use a PC (normally a Laptop) for display profiling via its HDMI output, first connect the display to calibrated to the HDMI output, set the desktop to 'Extended' mode (not 'Clone' mode), and re-start the PC, so the display is correctly identified.

Extended Desktop

The above shows the standard Intel HD Graphic configuration for Extended Desktop, with the Second Display as the display to be profiled.

With any graphics card ensure you select the correct display to configure - usually the external HDMI connected display.

Extended Desktop

With the PC now connected to the display to be profiled set the PC desktop background to 'black', so when displaying the profiling patches the background is not intrusive, or potentially changing the profiling results, as with plasmas ABL.

Extended Black Desktop

Extended Desktop, with the left hand side being the LightSpace Laptop, and the right hand side the display being profiled.


ICC Profile and VCGT Management

ICC Profiles can be managed manually, if you know what you are doing. If you are unsure SpaceMatch DCM can be used to verify the status of any active ICC profile and the graphics card's VCGT, and can re-set any found active to Null, as is needed for accurate HDMI output.

Using a true Null LUT to replace the VCGT data is critical, as outlined above.

SpaceMatch DCM

The above shows an active ICC profile as reported via SpaceMatch DCM. Thsi needs to be re-set to a Null profile before the HDMI output can be used for display profiling, which SpaceMatch DCM can do using a true Null LUT generated via LightSpace CMS.


Graphics Card Setup

The PC graphics card, or graphics chip-set, needs to be set to standard default settings, as any setting changes will again distort the HDMI output.

Graphics Card Settings

The above shows the Null settings for an Nvidia graphics card, with all settings set to their default values, and the below the same for the Intel HD Graphics chip-set.
(Note: the VCGT must be set to a true Null status via the user of SpaceMatch DCM and a true Null 3D LUT.(

Graphics Card Settings

The above Graphics Card controls can use DDC-IC / MCCS commands and protocols to directly adjust the display where applicable, or directly adjust the graphics card output. For accurate calibration it is therefore necessary to 'Null' all such settings, to enable the LightSpace CMS calibration to operate as required.


EDID

EDID is important for HDMI use for patch generation, as the protocol can be difficult to manage if it operates incorrectly, due to incorrect display and graphics card communication. Luckily, such problems are few and far between with modern displays and graphics cards.

DDC-CI and MCCS can effectively be ignored, so long as all graphics card settings are set to Null, as above.

EDID on the other hand attempts to ensure the image signal supplied by the graphics card is compatible with the display's expectations. That is all well and good when the communication is accurate, but can be a pain to overcome if the communication is inaccurate.

Inaccuracies are usually incorrect black and white levels, and are usually obvious to see, as defined in the Data vs. TV Legal Levels user guide.

With some graphics cards, such as Nvidia shown below, you can use the 'video' mode to compare the main graphics card output to the video output.

Graphics Card Settings

These settings change the black/white point for video output (only visible when the video is playing!), enabling a comparison to be made with the desktop output.

Graphics Card Settings

The above shows a live video stream set to 16-235 TV legal levels, with the desktop background set to 0-255 data levels.

When EDID goes wrong there are a number of options, depending on the graphics card or chip set being used.

ATI graphics cards have a manual option to force the card's output to data or TV legal ranges (0-255, 16-235).

Nvidia graphics cards do not have the same option, but can be forced via a utility file - such as NV_RGBFullRangeToggle.exe - if needed (although this is not always successful, depending on your graphics card drivers).
An alternative approach to force data range (0-255) is to set a 'custom resolution' (using the actual resolution figures), with a Hz rate that is slightly different to the expected standard - say 59Hz, rather than the standard 60Hz.


Dr HDMI

One device we have found rather useful with EDID issue is the small Dr HDMI box.

Dr HDMI

This allows independent control of most aspects of the HDMI signal, and we have used it will great success to overcome all issues we have not been able to manage with other approaches.

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