Encoding and decoding HDR videos

A high dynamic range video encoder circuit comprising:

• a dynamic range optimizer circuit, wherein the dynamic range optimizer circuit comprises a luma mapper and a range stretcher,
• wherein the luma mapper is arranged to apply a first luma mapping to an input pixel luma of a an input image yielding an intermediate pixel luma, and
• wherein the range stretcher is arranged to map the intermediate pixel luma to a zero when the intermediate pixel luma is equal to an offset yielding a first luma,
• a gain limiter,
• wherein the gain limiter is arranged to apply a second mapping on the input luma yielding a second luma,
• wherein the gain limiter is arranged to determine an output luma of a pixel by selecting the larger one of the first luma and the second luma.

A method of high dynamic range video decoding comprising:

• receiving an input image
• calculating a high dynamic range image from the input image,
• wherein the high dynamic range image comprises at least one output pixel,
• wherein the at least one output pixel has an output luma,
• wherein the calculating comprises:
• applying a first luma mapping to a input pixel luma of the input image yielding an intermediate pixel luma;
• and
• applying a stretched range mapping to the intermediate pixel luma to an offset when the value of intermediate pixel is a zero yielding a first luma;
• determining a second luma mapping function,
• calculating a second luma using the second luma mapping function,
• selecting an output luma as the smaller one of the first luma and the second luma.

A method of high dynamic range video encoding comprising:

• applying a first luma mapping to an input luma of an input image yielding an intermediate pixel luma;
• applying a stretched range mapping to the intermediate pixel luma to a zero when the intermediate pixel luma is equal to an offset yielding a first luma;
• and
• calculating a second luma the calculating comprising:
• applying a second luma mapping to the input luma,
• selecting the output luma to be the larger one of the second luma and the first luma.