HDR & Colorspace Feature - Grass Valley · Alchemist Live supports the following HDR processes. Up-mapping of SDR to HDR. Down-mapping of HDR to SDR. Cross-mapping of HDR to other

GV Live

HDR & Colorspace Feature

Alchemist Live – HDR & Colorspace

Version Number: 1.2 © 2020 GV Page 2 of 27

Version History

Date Version Release by Reason for Changes

31/10/2019 1.0 J Metcalf Initial release

20/01/2020 1.1 J Metcalf Update

26/05/2020 1.2 J Metcalf Added LUT section


Page 3 of 27 © 2020 GV Version Number: 1.2

Table of Contents

1. Introduction ............................................................................................................................... 4

2. HDR and Colorspace Controls ................................................................................................. 6

2.1 Color Space Conversion: Auto / REC601 / BT709 / BT2020 ..................................................... 7

2.1.1 Input Color Space ............................................................................................................. 7

2.1.2 Output Color Space ........................................................................................................... 8

2.2 HDR Conversion ...................................................................................................................... 9

2.2.1 Enable. ........................................................................................................................... 10

2.2.2 Color LUT ....................................................................................................................... 11

2.2.3 Input ............................................................................................................................... 12

2.2.4 System Gamma (input) ................................................................................................... 13

2.2.5 SDR Range (input) .......................................................................................................... 14

2.2.6 HDR Range (input) .......................................................................................................... 15

2.2.7 Output ............................................................................................................................. 16

2.2.8 Gain Adjustment.............................................................................................................. 20

2.2.9 Soft Clip Level: ................................................................................................................ 21

3. Color LUTs .............................................................................................................................. 23

3.1 Scan USB .............................................................................................................................. 23

3.2 Upload ................................................................................................................................... 24

3.3 Upload All .............................................................................................................................. 24

3.4 LUT Cache ............................................................................................................................ 25

3.5 Delete .................................................................................................................................... 25

3.6 Configuring a job using a LUT ................................................................................................ 26

3.6.1 Color Space Conversion.................................................................................................. 26

3.6.2 HDR Conversion ............................................................................................................. 26

3.6.3 BBC LUTs ....................................................................................................................... 27

No table of figures entries found.



1. Introduction

Alchemist Live offers a feature set for handling HDR (High Dynamic Range) and WCG (Wide Colour Gamut) content. Control sets are offered that are completely independent of each other.

Alchemist Live may be configured allowing the following configurations:

SDR / REC601

SDR / BT709

SDR / BT2020

HDR / BT601

HDR / BT709

HDR / BT2020

A process converting SDR to HDR will create content that will look correct when displayed on an HDR Monitor.

The process does not create an artificial HDR appearance. The content will still have the appearance of SDR.

A process converting the HDR to SDR will create content that will look correct when displayed on an SDR Monitor. The process will effectively remove the HDR appearance from the content and will have the appearance of native SDR content.

HDR – High Dynamic Range:

Alchemist Live includes a full suite of HDR processing tools.

Alchemist Live supports the following HDR processes.

Up-mapping of SDR to HDR.

Down-mapping of HDR to SDR.

Cross-mapping of HDR to other HDR formats.

Retention of HDR, source to output

WCG – Wide Colour Gamut

Alchemist Live now includes support for WCG.

Alchemist Live can convert between:

REC601

BT709

BT2020



Alchemist Live employs the following transfer functions:

Input:

PQ in: PQ EOFT (converts electrical in to display linear light domain)

BT709 in: BT709 EOTF (converts electrical in to display linear light domain)

HLG in: HLG inverse OE followed by HLG OO function

(converts electrical in, to display linear light domain using HLG input system gamma)

Slog3 in: Slog3 inverse OE followed by HLG OO function

(converts electrical in to display linear light domain using HLG input system gamma. This isn’t standardized as Sony don’t publish a display function)

Output:

PQ out: PQ inverse EOFT (converts display linear light to electrical)

BT709 out: BT709 inverse EOFT (converts display linear light to electrical)

HLG out: HLG inverse OO function followed by HLG OE

(converts display linear light to electrical using HLG output system gamma)

Slog3 out: HLG inverse OO function followed by Slog3 OE

(converts display linear light to electrical using HLG output system gamma, as above, this isn’t standardized)



2. HDR and Colorspace Controls

The HDR and Colorspace menus are located in the Utilities menu:

Color space control set

HDR control set



2.1 Color Space Conversion: Auto / REC601 / BT709 / BT2020

2.1.1 Input Color Space

In Auto mode, if the input is:

SD, it will be assumed that the source is compliant with REC601.

HD, it will be assumed that the source is compliant with BT709.

UHD/4K, it will be assumed that the source is compliant with BT709.

The User can manually force the desired Input Color Space setting. This is important when inputting sources compliant to BT2020, as currently there is no automatic detection of Color Space and the input won’t be assumed to be BT2020.



2.1.2 Output Color Space

In Auto mode, if the output is:

SD, it will comply with REC601.

HD, it will comply with BT709.

UHD/4K, it will comply with BT709.

The User may choose to manually force the desired Output Color Space setting:

If it is desired that the output be BT2020, then the control should be set to:

BT2020



2.2 HDR Conversion

Alchemist Live supports HDR.

Supported transfer functions are:

BT709 (SDR)

PQ

S-Log 3

HLG

Custom LUTs

Note: although HDR10 doesn’t appear in the menu, HDR10 employs the same HDR curve as PQ, hence HDR10 content can be processed by configuring as PQ.

Alchemist Live supports the following conversion modes:

Retention of SDR

Conversion from HDR to SDR

Conversion from SDR to HDR

Retention of HDR

Translation of HDR



2.2.1 Enable.

Note that in its default state, the HDR Conversion menu will be greyed out (unavailable).

To make the controls active it is first necessary to configure the checkbox: Enable

Once enabled, the HDR Conversion menu will become active.



2.2.2 Color LUT

Introduced in V2.1.0.20 Alchemist Live supports Custom LUTs (Look Up Tables).

LUT files should be in the form of .cube

The procedure of loading LUTs into the Alchemist Live system is described in the Color LUTs menu described in Section 3 below.

A LUT will describe the overall characteristic from input to output. The LUT will take priority over the setting of Input Transfer Function and Output Transfer Function.

Once LUT 1 and LUT 2 are loaded, they will appear in the Color LUT menu.

Up to two LUTs can be loaded at a time. Either LUT can be easily applied to a particular conversion process.

Alchemist Live can store many LUTs, but only two may be loaded into the LUT Cache (in the Color LUT menu) at a time.



2.2.3 Input

Input Transfer Function

The Input control allows the Operator to define the input with respect to HDR.

If an SDR to HDR process is to be configured, the input should be defined as: BT709 (SDR).

The default setting is: BT709 (SDR)



2.2.4 System Gamma (input)

This control is only active when the input HDR standard is defined to be either HLG or S-Log3.

It is not relevant for inputs that conform to PQ, or SDR formats and the control will be greyed out.

When active, Input System Gamma may be defined to a value between 1.0 and 2.0.

The default setting is: 1.2

Note – this is an input control and defines the brightness of the HDR input. A higher setting will result in a darker output picture.

System gamma is implemented in accordance with ITU-R Recommendation BT.2100

Input System Gamma = 1.2 (default)

Input System Gamma = 1.0

Input System Gamma = 1.5



2.2.5 SDR Range (input)

This control is only active when the conversion mode is SDR to HDR. The control is used to define how bright the SDR input is. The desired setting can be configured using the drop-down menu.

The range of the control is: 20 to 3000 nits.

The default value is: 200 nits

Note - The higher the nit level set, the brighter the output picture will be.

Input SDR Range = 200 nits (default)

Input SDR Range = 100 nits

Input SDR Range = 300 nits



2.2.6 HDR Range (input)

This control is only active when the input is defined to be HDR compliant. The HDR Range may be set to Auto, Full or Narrow, using the drop down menu.

In Auto mode outputs compliant to:

PQ will be set to Full

HLG will be set to Narrow

S-Log3 will be set to Narrow

When set to Full sub-blacks and super-white luminance values are included.

When set to Narrow sub-blacks and super-whites are clipped.



2.2.7 Output

Output Transfer Function

The output control allows the Operator to define the output with respect to HDR.

If an HDR to SDR process is to be configured, the output should be defined as: BT709 (SDR).

The default setting is: BT709 (SDR)

Note that if it is a requirement that the output conform to HDR10, the output should be set to PQ. PQ and HDR10 employ the same HDR curve so setting PQ will effectively make the output compliant to HDR10



System Gamma (output)

This control is only active when the Output HDR standard is defined to be either HLG or S-Log3.

It is not relevant for outputs that conform to PQ, or SDR formats and the control will be greyed out.

When active, Output System Gamma may be defined to a value between 1.0 and 2.0.

The default setting is: 1.2

Note – this is an output control and a higher setting will result in a brighter output picture.

System gamma is implemented in accordance with ITU-R Recommendation BT.2100

Output Gamma = 1.2 (default)

Output Gamma = 1.0

Output Gamma = 1.5



SDR Range (output)

This control is only active when the conversion mode is HDR to SDR. The control is used to define the SDR brightness of the output.

The range of the control is: 20 to 3000 nits.

The default value is: 200 nits

The higher the nit level set, the darker the output picture will be.

Output SDR Range = 200 nits (default)

Output SDR Range = 100 nits

Output SDR Range = 300 nits



HDR Range (output)

This control is only active when the output is defined to be HDR compliant. The HDR Range may be set to Auto, Full or Narrow, using the drop down menu.

In Auto mode outputs compliant to:

PQ will be set to Full

HLG will be set to Narrow

S-Log3 will be set to Narrow

When set to Full, sub-blacks and super-white luminance values are included.

When set to Narrow, sub-blacks and super-whites are clipped.



2.2.8 Gain Adjustment

The Gain adjustment control allows the User to adjust the brightness of the output picture.

The control scale is 0.1 to 10.00

Default value is 1.00

Setting a higher value will make the output picture brighter.

Gain adjustment = 1.0 (default)

Gain adjustment = 0.5

Gain adjustment = 1.5



2.2.9 Soft Clip Level:

The control scale is 60 to 100%

Default value is dependent upon the conversion being performed:

If the process is:

SDR to HDR, the default values is: 100%

HDR to SDR, the default values is: 80%

HDR to HDR, the default values is: 100%

Note that if the conversion mode configured is: BT709 (SDR) to BT709 (SDR), these controls will be unavailable (greyed out).

This effect of this control is to ‘clip-off’ the peak white.

If a typical HDR curve is shown on the left below. The effects of the white Clip control are shown on the right:

White clip activated

x



The effect of the White Clip control is to increase detail in the high luminance areas of picture. This maybe important when there are high luminance levels in the source:

The following example depicts an HDR to SDR conversion in content that has high luminance and demonstrates a practical example of when the white clip control may have a benefit:

White Clip control disabled example:

White Clip control enabled example:

This example demonstrates how the White Clip control can be used to retrieve detail in the high luminance areas of the picture.



3. Color LUTs

The Color LUTs menu is used to load LUTs.

LUTs in the form of a .cube file, are loaded from a USB Drive inserted into the Alchemist Live mainframe.

3.1 Scan USB

When pressed, the inserted USB Drive will be scanned. Any LUT in the form of .cube files, will appear in the USB *.cube files… field:

A LUT may be selected in the USB *.cube files… field.



3.2 Upload

Pressing the Upload button will result in the selected LUT appearing in the Available LUTs field.

3.3 Upload All

Pressing the Upload All button will result in all the available LUTs appearing in the Available LUTs field.



3.4 LUT Cache

A LUT may be assigned to either the LUT 1 Cache or LUT 2 Cache, using the associated drop down menu:

Note 1 – the same LUT cannot be loaded into both LUT 1 Cache, or LUT 2 Cache at the same time.

Note 2 – a LUT in the LUT Cache cannot be changed if it is active in the HDR Conversion menu.

The LUT may be applied to a conversion by selecting it in the Utilities/HDR menu:

3.5 Delete

LUTs maybe deleted from the Available LUTs field, by first selecting the LUT to be deleted, then checking the Allow Delete box and then pressing the Delete button:



3.6 Configuring a job using a LUT

The application of LUT is designed to ensure a specific HDR process may be easily configured …

When a LUT is selected and applied, with the exception of the HDR Range controls, all other HDR controls are disabled. This is because the configuration of these parameters is controlled by the LUT.

3.6.1 Color Space Conversion

LUTs are defined in RGB and do not specify Color Space, hence colour space conversion is not included in parameters controlled by the LUT. Therefore it is necessary for the Colour Space Conversion menu to be manually configured by an Operator.

3.6.2 HDR Conversion

When employing a LUT as part of an HDR conversion process, with the exception of the HDR Range controls, all the other HDR controls are disabled:

The Input and Output HDR Range controls may be configured using the relevant drop-down menu:

The HDR Range may be set to Narrow or Full.

Note that when a LUT is in use, the Auto is disabled

and cannot be selected, and the default setting is Full.

Note that the Input Transform Function and Output

Transform Function settings are ineffective when a

LUT is in use.



3.6.3 BBC LUTs

BBC LUTs maybe described by Type:

Type I - LUTs are intended for software applications, and older LUT devices that do not operate over the full 10-bit SDI signal range.

Type II - LUTs are intended for full-range SDI input signals such as S-Log3 and those

produced by some PQ devices.

Type III - LUTs are intended for LUT devices that process narrow-range video signals, but which operate over the full 10-bit signal range (0 to 1023). They will therefore pass sub-blacks and super-whites (required for ITU-R BT.814 HDR PLUGE and ITU-R BT.2111 HDR Colour Bars), so are most suitable for broadcast TV applications.

Alchemist Live HDR Range Settings:

Type I

Input HDR Range – Narrow

Output HDR Range – Narrow

Type II

Input HDR Range – Full

Output HDR Range – Narrow

Type III

Input HDR Range – Full

Output HDR Range – Full

Documents

HDR & Colorspace Feature - Grass Valley · Alchemist Live supports the following HDR processes. Up-mapping of SDR to HDR. Down-mapping of HDR to SDR. Cross-mapping of HDR to other