Mastering High Dynamic Range Content Using Dolby Vision™

Lustre is Dolby Vision Enabled and exposes additional UI elements when a suitable Dolby Content Mapping Unit connected to your Lustre system is detected. You should contact Dolby directly for information on how to obtain a Content Mapping Unit for use with Lustre.

Lustre allows you to perform Trim Passes on top of your High Dynamic Range master reference in order to adapt the HDR graded version to lower dynamic range display devices and help preserve colour intent for a variety of deliverables.

This topic covers system and setup requirements for this feature and describes the workflow.

System Requirements

You need a correctly configured workstation running Flame, Flare, Flame Assist, or Lustre and the following:

• An AJA Kona 3G or AJA Kona 4 video IO board.
• An available Ethernet port.

You also need a suitable Content Mapping Unit hardware device from Dolby in order to activate the user interface used to produce HDR grades from Lustre. Please contact Dolby directly for information on how to obtain the required hardware.

Setting Up Lustre for generating Dolby Vision™ metadata

First, connect the Content Mapping Unit hardware to your Lustre workstation. Refer to the Dolby documentation for specific instructions regarding the configuration of the Content Mapping Unit in particular networking configuration.

Second, connect the AJA video outputs to the Content Mapping Unit video inputs and make sure the Lustre system and the Content Mapping Unit can 'ping' each other over the network.

Last, configure the video output to use an RGB 4:4:4 12 bits raster in order to access the additional user interface and perform HDR mastering work. See Selecting a Raster for Playout. You can also save the selected raster as a project preference.

Typically, you will have an HDR reference "mastering" display being fed directly with your HDR graded images and one or more lower quality "target" displays for which you are generating the Dolby Vision metadata that are fed via the Content Mapping Unit.

Additional User Interface Elements for using Dolby Vision™

When a 12 bits video raster is enabled and a Content Mapping Unit is detected by Lustre, new buttons appear in the Lustre interface.

• In the view selector section, the D button changes to an H.

  

  Note: HDR mastering using Dolby Vision is only possible while the H view is selected.

• In the Colour menu, the DCM button appears. It allows you to access the Trim pass controls.

  

Dolby Vision™ HDR Metadata Workflow

Dolby Vision mastering is the process by which a High Dynamic Range graded reference is optimized, or trimmed, to make the best use of the capacities of a lower dynamic range display. In Lustre, Dolby Vision mastering is performed in real-time using the available Dolby Vision controls. The generated metadata is streamed instantly to the connected Content Mapping Unit and the results can be viewed immediately on the target display.

The analysis supports dissolves and animated trims. The resulting metadata from the Dolby Vision mastering can then be exported in an XML format to accompany the original HDR reference media.

Before you begin the Dolby Vision mastering process you need to have a finished HDR timeline that has been graded for your HDR reference display. The Dolby Vision mastering process simply creates metadata to accompany these image files, the image files are not changed.

Steps required for Dolby Vision mastering:

1. Create a new Colour grade version.

   This colour grade should be empty and is only used to link the HDR grade to Lustre's metadata files.

2. Create an HDR setup.

3. Perform HDR mastering.

4. Save the HDR setup.

Creating an HDR Setup

The Dolby Vision metadata is saved in a separate file that is distinct from the grade file. It is saved alongside the colour grade file in the Lustre project Library folder. Follow these steps to create an initial setup file for your work.

1. In the Main menu, click Setup and then click Grade. The Grade menu appears

2. From the Grade list, load the grade that you wish to associate with an HDR setup.

   

   Note: Although grading controls are disabled when performing HDR mastering it is recommended that you use a dedicated colour grade setup for HDR mastering work

3. Click 'H'

   

4. Select the media origin to be used during the trim pass work. Click Enable Source if you are starting with a new reference timeline that does not have any Lustre grading done or if you want to use the currently loaded grade.

   Enable Rendered if you are generating Dolby Vision metadata in the same project for which you have just generated your HDR reference grade using the Lustre grading controls (in other words, P view represents your reference HDR grade).

   In any case, if you make any changes to your Lustre reference grade you need to re-render, redo the Dolby analysis, and then readjust your Dolby trim values for the modified shots.

   

   Note:The grading controls are disabled in 'H' view

5. In the HDR field enter an HDR setup name.

6. Click New. The setup name is added to the list of setups for the grade.

You are ready to start the Trim Pass work.

Performing Dolby Vision™ mastering

Once the HDR setup file is created you are ready to start HDR mastering work. In this section, learn how to:

1. Access the Dolby Vision controls and select a Target display
2. Perform initial colour analysis
3. Perform additional Trim work.

Accessing the Dolby Vision™ controls

1. In the Main menu, click Colour, and then click DCM. The HDR menu appears.

2. Initially the entire user interface is greyed out, until you click Enabled.

   

3. Click Enabled to instruct Lustre to fetch the Mastering Display and Target Display characterizations from the Content Mapping Unit. This populates the corresponding drop down lists from the data transmitted by the Content Mapping Unit.

   

   Note: The Content Mapping Unit only knows about a pre-determined set of Mastering and Target displays. Select the ones that correspond to your displays. Please consult appropriate vendor documentation for details on display characterization.

4. If more than one Content Mapping Units are detected, the CMU drop-down lists only the first one that was detected.

Performing initial colour analysis

The HDR reference master must first be analyzed to produce base level metadata. The base level metadata is shot based and every shot in the timeline can have a different set of base level metadata.

1. Select a colour transform to bring the HDR master to linear colour space for analysis.

   

   Note: The choice of colour transform depends on the colour space of your HDR reference master. The most common scenario is for the HDR reference master to be encoded for a display calibrated to SMPTE ST-2084 (also known as PQ) and with P3 primaries and to have the Dolby Pulsar to be selected as the Mastering Display. The PQ_encoding_to_nits.ctf in the Autodesk colour transform collection (gamma directory) is the appropriate transform to select in this case (it simply converts the PQ values to nits without changing the primaries). Advanced users may need a different transform and this can often be built by going into Render/Output, assembling a Custom colour transform that does the appropriate conversion, and exporting it for use in this menu. The transform you use needs to convert the colour space of your HDR reference master into linearized radiance values in units of candelas per square meter (nits) and in the primaries of the HDR Mastering Display that is selected in the Content Mapping Unit.

2. From the drop down list, select whether to perform the analysis on the current shot, set of selected shots or the whole timeline

3. Click Analyse, the analysis starts and the images are analyzed one by one to produce the base level metadata.

4. If your footage is letterboxed: Letterboxing throws off the analysis results. Use the controls in Render/Resize to crop the image to remove any letterboxing. At this time we recommend cropping the image so that no black bars are sent to the Content Mapping Unit.

   Use the Canvas/Image Ratios fields to quickly see the current crop state of the image. If both the Image and Canvas match, the whole canvas was analyzed. If the Image ratio differs from the Canvas ratio, then only the area defined by the Render/Resize crop was analyzed.

Performing additional Trim passes

It may be necessary to further adjust the look for certain shots. Once the analysis has been performed for a shot, the Trim controls become available to help refine the shot's look

1. Click Trim for Display, for the trim controls sliders to become available

   

2. Adjust the controls to obtain the desired look for the shot.

3. The Trim controls can be animated for any shot using standard animation controls.

   Note: When in H mode, only the HDR mastering controls are visible in the Animation panel.

Saving and Loading an HDR setup

From time to time it is necessary to save your work. You can choose to create a new version of your work by entering a new name in the HDR setup field and by clicking New. You can also overwrite the current setup by clicking on the Save button. The current HDR setup is also saved when you save the current colour grade.

You can load a previously created HDR setup to review previous work or to continue work on a project.

To load an existing HDR setup

1. Enter the H mode by clicking the H button in the view selector.
2. Select the HDR setup you wish to load.
3. Click Load.

The selected HDR setup is loaded along with the associated colour grade.