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Purpose

 

To legalize input media, with optional soft-clipping control.

This node will "Legalize" luminance levels in the context of Broadcasting standards (e.g., ITU-R BT.601, BT.709, ...), that is, white levels must not exceed 100% (100 IRE on a waveform monitor), black levels must not drop below 0%, and so on. In 10-bit systems, the legal 0% to 100% luminance range correspond to the digital values from 64 to 940, while the 0..63 (Super-Blacks) and 941... 1024 (Super-Whites) ranges are  reserved for broadcasters usage or simply forbidden by them. These are some reasons for this requirement in modern times:

- In modern High Dynamic Range (HDR) workflows, broadcasters frequently use strict reference curves to ensure whites remain consistent without clipping.

- Several compression codecs use smooth mathematical functions that need to interpolate over sharp changes in nearby areas, which can briefly send the compressed signal out of range. In these cases the extra ranges provide headroom to avoid surpassing the technical limits (which could produce inverted colors and other artifacts depending on the video equipment). Note that this particular situation could still happen when that type of encoders are used after the Legalize node. To avoid this you can use other encoders not having this limitations, but if that is not possible and QC is not passed then you may need to apply extra intermediate processes to the images (such as luminance compression, or introducing some subtle noise, or other techniques).  

Note that the above standards refer to YUV 422 media exclusively. If your content is RGB you may need to use the RGBLevels effect and/or conversion to YUV color space before being able to use this node.

Note that this node will not render a new media file by itself, so it will need to be connected to posterior encoder nodes with render capabilities.

 

Inputs

 

Input_1: Media files to be legalized

 

Outputs

 

Output:  Media files with legalization applied.

 

Standard properties

 

Object Name

Color

File Path

Bypass

Lock

 

 

Node specific properties

 

Cleanup 422 (Off, On): Prevents values outside the legal RGB value of scope when sub sampling from RGB444 to YUV422.

 

Soft Black (Soft Black Knee, Soft Black Peak): Knee and peak values for compression of super black values into the legal range.

 

Soft White (Soft White Knee, Soft White Peak): Knee and peak values for compression of super white values into the legal range.

 

 

Developer reference (API Rest - node/Legalize/property/[Property ID])