Topics covered in this article:
- Creation of L1 metadata
- Dolby Vision Analysis tool
- Values contained in L1 metadata
In order to create and deliver Dolby Vision content, the HDR Master grade must be accompanied by dynamic Dolby Vision metadata that is essential to playing back the content correctly on Dolby Vision devices. Since this metadata is vital to Dolby Vision, it is recommended that it be created under colorist supervision during the color correction process.
Creating Dolby Vision metadata involves three main steps:
- Creating L1 metadata using Dolby Vision analysis,
- Checking the mapping using the eCMU/iCMU,
- Adjusting/modifying the metadata using Dolby Vision trim controls (optional – only if and when required by the creatives).
Creating L1 Metadata using Dolby Vision Analysis
The first step is to run the analysis to create L1 metadata. The Analysis tool (or Analyzer) is built into color correction systems that support Dolby Vision and is used to analyze an image and produce L1 Dolby Vision metadata. The analysis tool is not a plug-in but instead is built natively into partner solutions like color-grading systems and mastering systems.
After completing the HDR Master grade, the colorist runs the Dolby Vision analysis on all the media on the timeline, and the tool performs a pixel-level, frame-by-frame analysis subsequently producing and storing three values per shot that mathematically define the luminance range of each shot. The three values are:
- Minimum (min) – Lowest black level in the shot
- Average (mid) – Average luminance level across the shot
- Maximum (max) – Highest luminance level in the shot
These three values together are referred to as L1 (or Level 1) metadata and form the basis of Dolby Vision content and display mapping. L1 metadata is unique for every shot and is therefore referred to as dynamic metadata.
A Dolby Vision Master (PQ encoded images or video) delivered along with L1 metadata can fully enable Dolby Vision mapping and playback on any supported device. The Dolby Vision Master can also be used to derive other derived deliverables like HDR10 and SDR. We recommend checking and reviewing the mapping with L1 metadata, modifying it if required to better match the creative intent.