HDR Color Space Conversions

HDR Color Space Conversions

Introduction

Thanks to it's advanced Color Management System,  MIST allows all types of color space conversions, also including to and from HDR.
There is three type of HDR conversions possibles:
  1. Cross convert (HLG to HDR10 or HDR10 to HLG)
  2. Down convert (HDR10 to SDR* or HLG to SDR*)
  3. Up convert (SDR* to HDR10 or SDR* to HLG)

* SDR includes all type of standard dynamic range color spaces: REC709, DCI P3, etc.

Basic Principle

In order to perform a color space conversion, it is mandatory that the 3 main elements permitting the color management are carefully defined.


The Working Color Space

This is the color space of the Composition. It is the central element of the color management.

The parameters of the Working Color Space (metadata) are defined in the Composition Settings > CMS menu.

In order to perform a color space conversion, the Color Management System must be set on MTCMS. 
Usually the working color space is defined according to the type of delivery we want to perform, but it is not mandatory as MIST can create multiple deliveries from a single composition.

When monitoring the content using the video output (SDI out or HDMI), it is the Working color space that is sent with the video parameters.

The Mastering Display

The Mastering Display is another key element of the working color space for HDR conversions. It defines the relationship between the different scales used for the conversion (such as PQ and HLG). 
If the mastering display is present as metadata in the file, MIST will retrieve it automatically, otherwise it must be manually set in the Composition Settings > DISPLAY menu.
It is absolutely necessary to set this information correctly particularly when working with HLG workflows.

See also Color Management in MIST User Manual.

The Source Color Space

The source color space is usually defined by the metadata of the clip / media. MIST reads the metadata and automatically adjust the Compositions settings accordingly when they are present in the clip / media file.
Because you can mix the formats on the same track of a composition, it is necessary to carefully control these parameters for each clip.
They are defined in the GRADE > Source menu.

The Dynamic Range Conversion mode

The Source qualification allows to assign a specific conversion method to apply for the HDR conversion, according to the type of media (broadcast or film).
Currently MIST and ICE offers three different kind of dynamic range conversions (DRC):
  1. STANDARD is based on the ITU-R-BT.2390 High dynamic range television for production and international programme exchange recommendation.
  2. FILM conversion mode is based on ITU-R-BT.2446 Methods for conversion of high dynamic range content to standard dynamic range content and vice-versa
  3. NBCU is the NBCU LUTs developed by NBCUniversal Media, LLC.

Gain, Saturation & Gamma controls
For the conversions using the methods STANDARD and FILM, it is always possible to make manual ajustements of the gain, the saturation and the gamma.
They are displayed at a percentage of the nominal value.
  1. for STANDARD DRC, the Gain at 100% is set on 203 nits, as per the ITU-R-BT.2390 recommendation for a working color space in HDR10 or HLG
  2. for FILM DRC, the Gain at 100% is mainly on 203 nits, with a peak around 400 nits for 100% white as per the ITU-R-BT.2446 recommendation for a working color space in HDR10 or HLG.

See also Source Settings in MIST User Manual.

The Output Color Space

The Output Color space or Target Color space is the one for the rendered file. MIST has two ways for rendering files.
  1. Rendering the current composition using the Master Delivery menu.
  2. Rendering multiple files from the current composition using the Flowgraph menu.
If the Color space parameters set in the master delivery panel or in a rendering node of the Flowgraph are different from the Working color space AND the CMS is MTCMS, then MIST will perform a conversion.


HDR Cross Conversions


There is 2 possibilities for converting within HDR color spaces:
  1. converting a HLG content into HDR10
  2. converting a HDR10 content into HLG
The conversions using one or the other of the ITU recommended methods are based on a mastering display of 1000 nits. For content created with 4000 nits and above, other conversions methods should be preferred (for example Dolby Vision).

HLG to HDR10

In order to convert from BT.2100 HLG to ST2084 PQ the following steps must be performed.

Step 1:  Set up of the Color Management System

    1. Choose MTCMS as color system in the Composition Settings > CMS menu.
    2. Workflow must be set on HDR10. This will update automatically the Primaries on BT.2020 and the EOTF on ST2084 (PQ) 
    3. In the Composition Settings > DISPLAY select BT.2100 PQ 1000 nits for the Mastering Display






Step 2: Qualification of the Source clip(s)

  1. Position the playhead on the clip you need to qualify. If you have several clips on the track with the same color space, select them all and in the GRADE panel choose GANG. If you have mixed color space, you need to set for each different color space the right parameters.
  2. In the SOURCE tab, verify that the Primaries are set on ITU-R BT.2020, the EOTF on ITU-R BT 2100 HLG and the Matrix on ITU-R BT.2020 as well.
  3. Verify the Range is set correctly.
  4. Select the Dynamic Range Conversion (DRC) mode
  5. Optionally adjust Gain, Saturation and Gamma





Step 3: Define the Output color space

  1. Whatever the output format you select, in the Master Delivery > VIDEO tab or in the Flowgraph's node Properties you will be able to modify the Color Space. In this case you need it to be set on ITU-R BT.2020 ST 2084 as you want to convert to HDR10
  2. Verify the Range
  3. Verify the Mastering Display is on BT.2100 PQ 1000 nits


HDR10 to HLG

In order to convert from ST2084 PQ to BT.2100 HLG the following steps must be performed.

Step 1:  Set up of the Color Management System

  1. Choose MTCMS as color system in the Composition Settings > CMS menu.
  2. Workflow must be set on HLG. This will update automatically the Primaries on ITU-R BT.2020 and the EOTF on ITU-R BT.2100 HLG 
  3. In the Composition Settings > DISPLAY verify the Mastering Display is on BT.2100 HLG 1000 nits





Step 2: Qualification of the Source clip(s)

  1. Position the playhead on the clip you need to qualify. If you have several clips on the track with the same color space, select them all and in the GRADE panel choose GANG.
  2. In the SOURCE tab, verify that the Primaries are set on ITU-R BT.2020, the EOTF on SMPTE ST2084 (PQ) and the Matrix on ITU-R BT.2020 as well.
  3. Verify the Range is set correctly.
  4. Select the Dynamic Range Conversion (DRC) mode (in this example we used NBU LUT)



Step 3: Define the Output color space

  1. Whatever the output format you select, in the Master Delivery > VIDEO tab or in the Flowgraph's node Properties you will be able to modify the Color Space. In this case you need it to be set on ITU-R BT.2020 HLG as you want to convert to HLG
  2. Verify the Range
  3. Verify the Mastering Display is the same settings than in the Composition's DISPLAY settings.




Up Conversions to HDR

MIST can easily convert any kind of SDR format, including REC709 or P3 DCI to either HLG or HDR10 color space.

SDR to HDR10

In order to convert from for example a REC 709 content to ST2084 PQ the following steps must be performed.

Step 1:  Set up of the Color Management System

  1. Choose MTCMS as color system in the Composition Settings > CMS menu.
  2. Workflow must be set on HDR10. This will update automatically the Primaries on BT.2020 and the EOTF on ST2084 (PQ) 
  3. verify the Mastering Display is on BT.2100 PQ 1000 nits





Step 2: Qualification of the Source clip(s)

  1. Position the playhead on the clip you need to qualify. If you have several clips on the track with the same color space, select them all and in the GRADE panel choose GANG.
  2. In the SOURCE tab, verify that the Primaries are set on REC 709, the EOTF on BT.1886 and the Matrix on REC 709 as well.
  3. Verify the Range is set correctly.
  4. Select the Dynamic Range Conversion (DRC) mode
  5. Optionally adjust Gain, Saturation and Gamma


Step 3: Define the Output color space

  1. Whatever the output format you select, in the Master Delivery > VIDEO tab or in the Flowgraph's node Properties you will be able to modify the Color Space. In this case you need it to be set on ITU-R BT.2020 ST 2084 as you want to convert to HDR10
  2. Verify the Range



SDR to HLG

In order to convert from for example a REC 709 content to BT.2100 HLG the following steps must be performed.

Step 1:  Set up of the Color Management System

  1. Choose MTCMS as color system in the Composition Settings > CMS menu.
  2. Workflow must be set on HLG. This will update automatically the Primaries on ITU-R BT.2020 and the EOTF on ITU-R BT.2100 HLG 
  3. Verify the Mastering Display is on BT.2100 HLG 1000 nits




Step 2: Qualification of the Source clip(s)

  1. Position the playhead on the clip you need to qualify. If you have several clips on the track with the same color space, select them all and in the GRADE panel choose GANG.
  2. In the SOURCE tab, verify that the Primaries are set on REC 709, the EOTF on BT.1886 and the Matrix on REC 709 as well.
  3. Verify the Range is set correctly.


Step 3: Define the Output color space

  1. Whatever the output format you select, in the Master Delivery > VIDEO tab or in the Flowgraph's node Properties you will be able to modify the Color Space. In this case you need it to be set  ITU-R BT.2020 HLG as you want to convert to HLG.
  2. Verify the Range



Down Conversions from HDR

MIST can easily convert HDR10 or HLG content to any SDR color space, like REC709 or P3 DCI.

HDR10 to SDR

In order to convert from for example a ST2084 PQ content to REC 709 for example the following steps must be performed.

Step 1:  Set up of the Color Management System

  1. Choose MTCMS as color system in the Composition Settings > CMS menu.
  2. Workflow must be set on SDR. This will update automatically the Primaries on BT.709 and the EOTF on BT.1886 
  3. verify the Mastering Display is on BT.2100 PQ 1000 nits



Step 2: Qualification of the Source clip(s)

  1. Position the playhead on the clip you need to qualify. If you have several clips on the track with the same color space, select them all and in the GRADE panel choose GANG.
  2. In the SOURCE tab, verify that the Primaries are set on ITU-R BT.2020, the EOTF on SMPTE ST2084 (PQ) and the Matrix on ITU-R BT.2020 as well.
  3. Verify the Range is set correctly.
  4. Select the Dynamic Range Conversion (DRC) mode 



Step 3: Define the Output color space

  1. Whatever the output format you select, in the Master Delivery > VIDEO tab or in the Flowgraph's node Properties you will be able to modify the Color Space. In this case you need it to be set  ITU-R BT.709 as you want to convert to SDR.
  2. Verify the Range
  3. Verify the mastering display




HLG to SDR

In order to convert from for example a HLG content to REC 709 for example the following steps must be performed.

Step 1:  Set up of the Color Management System

  1. Choose MTCMS as color system in the Composition Settings > CMS menu.
  2. Workflow must be set on SDR. This will update automatically the Primaries on BT.709 and the EOTF on BT.1886 
  3. verify the Mastering Display is on BT.2100 HLG 1000 nits


Step 2: Qualification of the Source clip(s)

  1. Position the playhead on the clip you need to qualify. If you have several clips on the track with the same color space, select them all and in the GRADE panel choose GANG. If you have mixed color space, you need to set for each different color space the right parameters.
  2. In the SOURCE tab, verify that the Primaries are set on ITU-R BT.2020, the EOTF on ITU-R BT 2100 HLG and the Matrix on ITU-R BT.2020 as well.
  3. Verify the Range is set correctly.
  4. Select the Dynamic Range Conversion (DRC) mode
  5. Optionally adjust Gain, Saturation and Gamma





Step 3: Define the Output color space

  1. Whatever the output format you select, in the Master Delivery > VIDEO tab or in the Flowgraph's node Properties you will be able to modify the Color Space. In this case you need it to be set  ITU-R BT.709 as you want to convert to SDR.
  2. Verify the Range
  3. Verify the mastering display




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