In this article, we will explore the topic of full and legal range levels and deliveries for Dolby Vision. We will cover the following topics:

 

• Terminology
• Full Range Video Monitoring
• Legal Range Video Monitoring
• File Export
• File Import
• Metadata Export
• DNxHR (intermediate)
• Summary

 

Before we go into more detail, let's take a look at the different terminology currently used to describe these data levels.

 

Terminology

Full Levels	Legal Levels
Full (Range)	Legal (Range)
Computer	Video (Range)
Extended	Limited
Data Levels	Studio (Range, Swing)
	Narrow Range
	SMPTE Range

 

 

We should not be confused by these different terms and instead take a closer look at the basics. In the remainder of this article, we will use the terms full range and legal range.

 

 

Full Range Video Monitoring

Modern color correctors used in computer-based workflows internally employ floating-point arithmetic. This allows for more precise and flexible calculations, as they are not limited to whole numbers (integers). However, when it comes to outputting the image through a video interface, it needs to be converted back to a format suitable for display on a monitor. Typically, this format is a 12 or 10-bit video signal.

 

10-bit Video Levels	Code Values
Full Range	0-1023
SDI Full	4-1019

 

 

 

 

 

 

12-bit Video Levels	Code Values
Full Range	0-4095
SDI Full	16-4079

 

 

 

 

 

 

A 10-bit video signal offers 1024 possible values for each color channel (red, green, and blue). These values span from 0 (representing black) to 1023 (indicating full intensity), with each integer value representing a specific brightness level for that color channel. To convert the floating-point values to a 10-bit video signal, the values are "quantized" or rounded to the nearest integer value within the 0 to 1023 range, resulting in a full video range output. When outputting in full range using an SDI infrastructure, the SDI full range utilizing 10 bits is defined from code value 4 to 1019. The first and last 4 bits are utilized for SDI signalling information. Consequently, when outputting from the color corrector in full range, it is necessary to ensure that your reference display input is also set to full range. 

The traditional Dolby Vision workflow recommendation to output in full range stems from the fact that the eCMU can only handle SDI signals in the full range format. When no eCMU is in use, signals are not required to be full range, so long as the SDI source and reference display(s) all use the same signal range settings.

 

 

 

 

 

 

Legal Range Video Monitoring

When opting for a Legal Range output, the quantization is performed to an integer value ranging from 64 to 940. This limited range ensures compliance with the legal or video range specifications for 10-bit video signals.

 

10-bit Video Levels	Code Values
Video Range	64-940

 

 

 

 

12-bit Video Levels	Code Values
Video Range	256-3760

 

 

 

 

 

If you’d like to output in legal range, you must ensure, that your reference display is setup accordingly.

 

 

 

 

 

Note:

The naming of Dolby Vision Mastering and Target Displays always includes "FULL" in their name. This is because all mappings are performed internally in full. Color correctors and mastering applications will scale these full range mapped images to the correct signal range on output.

 

 

Full and legal is not only a topic when it comes to monitoring, but also when it comes to rendering. Especially when exporting video to QuickTime ProRes.

 

 

  

File Export

We must consider that there are certain codec types, that expect RGB values – which are typically full range and that there are other codecs, that expect YCbCr values that are typically legal range.

Codecs that would expect full range data are tiff, Jpeg2000, dpx and others.

A good example for a codec that expects legal range data is ProRes. ProRes (all flavors) usually expects legal range data and consequently, color grading tools like Baselight or Resolve will automatically scale from full to legal range data levels when dealing with ProRes files. 

When rendering to ProRes, Baselight automatically applies a scaling to legal.

 

Resolve applies the same, when rendering to a ProRes and having the Data Levels set to Auto.

 

 

Baselight also brings up a warning, when rendering a ProRes file other than in legal range.

 

  

Now we know how software may handle ProRes on export, let‘s see how they handle ProRes on import.

 

 

File Import

Most modern postproduction software work in float or full range by default and may even scale imported video range files to full range automatically – basically those tools normalize video and work in 0 to 1 floating point.

Speaking for both of our examples used, Baselight and Resolve, this is true. And as you can see here in Baselight’s so called color space journey, they outline the processing happening here and you can see, that the imported ProRes file gets scaled from legal to full.

 

   

 

In Resolve, it’s not that obvious, as Resolve doesn’t offer such a view. However, there’s also a legal to full conversion happening on import. You can easily check this by navigating to the clip attributes and switching between the data level modes.

 

This legal to full scaling is a commonly seen default behavior for major post production software when iomporting ProRes data. However, there’s no file metadata indicator that would flag a ProRes file as legal or full range.

 

 

Note:
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.

 

 

 

Dolby Vision Metadata Export

When exporting Dolby Vision metadata from a color corrector, the Color Space and Signal Range are always set to RGB and Computer, which means full range - by default. 

This is due to the fact, that when exporting the Metadata, the color corrector is not aware of the video format you‘re going to export. Therefore, it assumes an export of the Dolby Vision master format of 16-bit TIFF which would expect RGB full range data levels.

 

 

When exporting a Dolby Vision IMF package, which uses JPEG2000 image compression, the Dolby Vision interleaved metadata will be labelled correctly as per the settings made for the respective IMF application.

When exporting to ProRes, you do not need to change the color space and signal range values inside the Dolby Vision metadata.

 

 

Note: 

When 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.

 

 

Using DNxHR as an intermediate file:

Some (predominantly Windows) users use DNxHR as an intermediate file to take the output from their Windows grading system, which can then be taken to a Mac based system for final encoding into ProRes. Like ProRes, DNxHR can be encoded as full or legal range. A majority of tools would interpret DNxHR (like ProRes) as legal range by default. Resolve will encode a DNxHR encoded file using video/legal levels (auto) and interpret an imported DNxHR file as legal range as well. Other tools may interpret DNxHR (especially their 444 variant), as full.
We recommend to not using any intermediate files without proper testing.

 

 

Summary

• Video monitoring via iCMU can happen in Full or Legal range
• Ensure that the input of your reference display matches to the video output of the color corrector (Full-Full or Legal-Legal)
• Using the eCMU requires a Full range video output from the color corrector
• Use the default data level setting (auto) when exporting your video
• There’s no need to change the Dolby Vision metadata for ProRes exports