This article covers the following FAQs on Dolby Vision mastering and quality control:

 

• What is the recommended Dolby Vision QC process?
• What are the Dolby Vision Professional Tools?
• Where can I get the Dolby Vision Professional Tools?
• Do I have to use the Dolby Vision Professional Tools?
• Should I export a Dolby Vision mezzanine file as QuickTime ProRes in full or legal range data?
• Why do MaxFall and MaxCLL values differ when using different HDR10 analyzers?
• Why do MaxFall and MaxCLL values differ when analyzing uncompressed vs. compressed and/or color subsampled vs. non subsampled content?
• How to set the <source-format> argument for ProRes Rec.2020 sources when calculating HDR10 metadata using cm_analyze?

 
 

What is the recommended Dolby Vision QC process?

Performing quality control is essential in order to ensure that the Dolby Vision metadata is valid and correctly mapping. Therefore, the HDR grade and the Dolby Vision Metadata should be checked for quality and integrity before leaving the color suite.

A Dolby Vision QC should always consist of
 

• Comprehensive visual QC
  • Review a mapped version using the content mapping functionality of a partner solution or
  • Review your Dolby Vision profile 8.4. encoded file on a Dolby vision capable device

 

• Metadata validation (for master and mezzanine delivery)
  • Using Metafier, which is part of the Dolby Vision Professional Tools

 

• Preliminary checks (for master and mezzanine delivery)
  • Duration, frame numbering 
  • Image specifications and information 
  • Color encoding fields
  • Mastering display information
  • Canvas and image aspect ratio

 

For more information see our Best Practices on Dolby Vision Quality Control.

 

What are the Dolby Vision Professional Tools?

The Dolby Vision Professional Tools are a set of command line tools that you would use to create and manage a Dolby Vision master and mezzanine deliverable.  Additionally, and at times required, you could use these tools to extract and update the Dolby Vision metadata from a Dolby Vision deliverable.

Dolby Vision Professional Tools include:

• cm_offline - Renders, with color mapping, a Dolby Vision Master to a specified target display
• mezzinator - Creates a Dolby Vision mezzanine MXF deliverable
• metafier - Dolby Vision metadata utility and validation tool
• cm_analyze - Generates Dolby Vision XML Metadata with Global and LEVEL 1 Analysis Metadata to convert existing HDR10 content to Dolby Vision content

These tools are delivered as executables and designed to run on Linux, MacOS X, or Windows systems. Choose the appropriate package for your operating system.


 

Where can I get the Dolby Vision Professional Tools?

Dolby Vision Professional Tools are available for download on Dolby Customer.
 

Do I have to use the Dolby Vision Professional Tools?

You do not have to specifically rely on the Dolby Vision Professional Tools.  A core subset of the Professional Tools’ functionality can be found in most major postproduction software.

Creators that deliver Dolby Vision mezzanine or master files to studio partners or OTT services should validate their content and it’s metadata by using Metafier if they have access to the Professional Tools. Please check with your studio partner on their specific QC requirements.

Should I export a Dolby Vision mezzanine file as QuickTime ProRes in full or legal range?

ProRes (all flavors) encoders usually expect legal/video range data and consecutively, color grading tools like Resolve or Baselight will automatically scale from full to legal range data levels when dealing with ProRes files.
On import, these tools will automatically decode and scale ProRes from legal to full. 
On export, these tools will automatically scale from their (internal) full range processing to legal data levels.

If not explicitly requested for by your customer and/or thoroughly tested, we recommend leaving any scaling or data range settings on their respective auto or default mode. 

When source images are ProRes encoded, Dolby Vision Professional Tools and downstream decoders ignore the <ColorSpace> and <SignalRange> field in the metadata (XML) and use the data delivered by Apple’s ProRes library instead of managing signal range values themselves. Therefore, Dolby Vision metadata associated with ProRes deliveries can be marked as either "Full/Computer" or "Legal/Video" without impacting mapping or downstream encoding.

Read more about Dolby Vision legal range workflows here .

 

Why do MaxFall and MaxCLL values differ when using different HDR10 analyzers?

Different analyzers may have implemented tolerance thresholds to mitigate light level issues caused by compression, color subsampling, and brief moments of brightness not indicative of the overall sequence characteristics. Depending on these thresholds, different analyzers may provide different static HDR10 metadata values

Why do MaxFall and MaxCLL values differ when analyzing uncompressed vs. compressed and/or color subsampled vs. non subsampled content?

Compression artifacts (especially at high-contrast edges), chroma reconstruction, and occasional very bright frames or flashes distort the MaxFALL and MaxCLL values. Most HDR10 analyzers have implemented tolerance thresholds to mitigate the problem, typically ignoring a small percentage of pixels based on chromaticity and luminance, allowing pixels to fall slightly out of gamut and generally ignoring some of the brightest frames that would otherwise make the MaxCLL and MaxFALL values not useful.
Ideally, HDR10 static metadata is computed from uncompressed, non-color-subtitled sources.


 

How to set the <source-format> argument for ProRes Rec.2020 sources when calculating HDR10 metadata using cm_analyze?

ProRes 4444XQ - ST.2084(PQ) Rec.2020 source

./cm_analyze –-bda –-source-format <bt2020 pq> --aspect-ratios <arg1> <arg2> <input.mov> <output.xml>
 

ProRes 422 - ST.2084(PQ) Rec.2020 source

./cm_analyze –-bda –-source-format <bt2020 pq> --aspect-ratios <arg1> <arg2> <input.mov> <output.xml>