Signal reshaping and coding for HDR and wide color gamut signals

A decoder for generating high-dynamic range video data, wherein the decoder comprises one or more processors and non-transitory memory, wherein generating an output image with the decoder comprises:

• receiving an input bitstream comprising sequence processing set (SPS) data and storing at least a portion of the SPS data in the non-transitory memory;
• parsing the SPS data;
• and upon detecting that an HDR extension syntax structure is present in the parsed SPS data:
• extracting from the HDR extension syntax structure post-processing information comprising an SDR viewable flag and one or more of a color space enabled flag, a color enhancement enabled flag, an adaptive reshaping enabled flag, a dynamic range conversion flag, or a color correction enabled flag, wherein the SDR viewable flag indicates whether a decoded version of the input bitstream is directly viewable on a standard dynamic range (SDR) display;
• decoding the input bitstream to generate a preliminary output decoded signal;
• and
• generating a second output signal based on the preliminary output signal and the post-processing information;
• wherein the adaptive reshaping enabled flag indicates that information related to adaptive reshaping is present,
• wherein the information related to adaptive reshaping comprises reshaping function parameters to determine a reshaping function based on one or more polynomial functions, and
• wherein the reshaping function parameters comprise:
• a first parameter based on a total number of polynomial functions used to define the reshaping function, and for each (pi) polynomial function in the reshaping function, further comprising:
• a starting pivot point for the polynomial function;
• a second parameter based on an order of the polynomial function, wherein the order of the polynomial function can't exceed the value of two;
• and
• one or more non-zero coefficients for the polynomial function.