Dynamic range converter with logarithmic conversion and methods for use therewith

Patent metadata

Field	Value
Publication number	US-2016205369-A1
Application number	US-201514867234-A
Country	US
Kind code	A1
Filing date	Sep 28, 2015
Priority date	Jan 9, 2015
Publication date	Jul 14, 2016
Grant date	—

Abstract

In various embodiments, a dynamic range converter includes at least one circuit including a logarithm base 2 (log 2) domain circuit that uses piecewise linear interpolation to perform as at least a portion of one of: a linearizer configured to convert nonlinear color space signals to linearized color space signals; a delinearizer configured to convert linear color space signals to nonlinearized color space signals; a chrominance tone mapper for scaling gamut shaped components in accordance with dynamic color transform metadata to generate chrominance mapped components; or a luminance tone mapper for scaling color remapped components in accordance with the dynamic color transform metadata to generate luminance mapped components. Other embodiments are disclosed.

First claim

What is claimed is:

1 . A dynamic range converter comprising:
at least one circuit including a logarithm base 2 (log 2) domain circuit that uses piecewise linear interpolation to perform as at least a portion of one of:
a linearizer configured to convert nonlinear color space signals to linearized color space signals;
a delinearizer configured to convert linear color space signals to nonlinearized color space signals;
a first tone mapper for scaling gamut shaped components in accordance with dynamic color transform metadata to generate first mapped components; or
a second tone mapper for scaling color remapped components in accordance with the dynamic color transform metadata to generate second mapped components.

2 . The dynamic range converter of claim 1 wherein the log 2 domain circuit includes:
at least one look-up table that convert an input signal into a log 2 domain signal and determines a slope and intercept based on a piecewise linear representation of a log 2 domain transfer function; and
an adder and a multiplier that generate an interpolated result by interpolating the log 2 domain signal based on the slope and intercept;
wherein the at least one look-up table generates an output signal based on an inverse log 2 conversion of the interpolated result.

3 . The dynamic range converter of claim 2 wherein the log 2 domain circuit further includes a programmable shifter that operates based on configuration data to scale a dynamic range of at least one of: the input signal or the output signal.

4 . The dynamic range converter of claim 2 wherein the input signal, x, represents a positive value less than 1 and wherein for values of x greater than T, the log 2 domain circuit operates in a reverse mode based on 1-x.

5 . The dynamic range converter of claim 4 wherein T is programmable.

6 . The dynamic range converter of claim 4 wherein the at least one look-up table includes a first table for the reverse mode and a second table for non-reverse mode operation.

7 . The dynamic range converter of claim 2 wherein the log 2 domain transfer function is programmable.

8 . The dynamic range converter of claim 2 wherein the log 2 domain transfer function represents one of: a electro-optical transfer function, a gamma function, an inverse electro-optical transfer function or an inverse gamma function.

9 . The dynamic range converter of claim 1 wherein the first tone mapper operates to:
generate a weighted maximum of the gamut shaped components, based on the dynamic color transform metadata;
obtain a scale factor for the gamut shaped components based on the log 2 domain circuit;
multiply the scale factor by corresponding ones of the gamut shaped components to generate scaled gamut shaped components; and
generate the first mapped components by inverse log 2 conversion of the scaled gamut shaped components.

10 . The dynamic range converter of claim 1 wherein the second tone mapper operates to:
generate a weighted maximum of the color remapped components, based on the dynamic color transform metadata;
obtain a scale factor for the color remapped components based on the log 2 domain circuit;
multiply the scale factor by corresponding ones of the color remapped components to generate scaled color remapped components; and
generate the second mapped components by inverse log 2 conversion of the scaled color remapped components.

11 . A method comprising:
operating a logarithm base 2 (log 2) domain circuit that uses piecewise linear interpolation to perform at least one of:
converting nonlinear color space signals to linearized color space signals;
converting linear color space signals to nonlinearized color space signals;
scaling gamut shaped components in accordance with dynamic color transform metadata to generate first mapped components; or
scaling color remapped components in accordance with the dynamic color transform metadata to generate second mapped components.

12 . The method of claim 11 wherein the log 2 domain circuit is further operated includes to scale a dynamic range of at least one of: an input signal of the log 2 domain circuit or an output signal of the log 2 domain circuit.

13 . The method of claim 11 wherein the input signal, x, represents a positive value less than 1 and wherein for values of x greater than T, the log 2 domain circuit operates in a reverse mode based on 1-x.

14 . The method of claim 11 wherein the operations of the log 2 domain circuit further include:
converting an input signal into a log 2 domain signal;
determining a slope and intercept based on a piecewise linear representation of a log 2 domain transfer function;
generating an interpolated result by interpolating the log 2 domain signal based on the slope and intercept; and
generating an output signal based on an inverse log 2 conversion of the interpolated result.

15 . The method of claim 14 wherein the log 2 domain transfer function represents one of: a electro-optical transfer function, a gamma function, an inverse electro-optical transfer function or an inverse gamma function.

16 . The method of claim 11 wherein the operations of the log 2 domain circuit further include:
generating a weighted maximum of the gamut shaped components, based on the dynamic color transform metadata; and
obtaining a scale factor for the gamut shaped components based on the log 2 domain circuit; and
multiplying the scale factor by corresponding ones of the gamut shaped components to generate scaled gamut shaped components; and
generating the first mapped components via an inverse log 2 conversion of the scaled gamut shaped components.

17 . The method of claim 11 wherein the operations of the log 2 domain circuit further include:
generating a weighted maximum of the color remapped components, based on the dynamic color transform metadata;
obtaining a scale factor for the color remapped components based on the log 2 domain circuit; and
multiplying the scale factor by corresponding ones of the color remapped components to generate scaled color remapped components and generating the second mapped components via an inverse log 2 conversion of the scaled color remapped components.

Assignees

• Vixs Systems Inc

Inventors

• Wallace Bradley Arthur

Classifications

• H04N5/20 Primary

  Circuitry for controlling amplitude response · CPC title

• H04N9/68

  for controlling the amplitude of colour signals, e.g. automatic chroma control circuits (H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86) · CPC title

• H04N9/67 Primary

  for matrixing (camera processing pipelines for matrixing of colour signals H04N23/85) · CPC title

• H04N9/64 Primary

  Circuits for processing colour signals (H04N9/77 takes precedence; camera processing pipelines for processing colour signals H04N23/84) · CPC title

• G06T2207/10016

  Video; Image sequence · CPC title