Systems, methods, and instrumentalities are disclosed for inverse shaping for high dynamic range (HDR) video coding. A video coding device, e.g., such as a decoder, may determine a plurality of pivot points associated with a plurality of piecewise segments of an inverse reshaping model. The plurality of pivot points may be determined based on an indication received via a message. Each piecewise segment may be defined by a plurality of coefficients. The video coding device may receive an indication of a first subset of coefficients associated with the plurality of piecewise segments. The video coding device may calculate a second subset of coefficients based on the first subset of coefficients and the plurality of pivot points. The video coding device may generate an inverse reshaping model using one or more of the plurality of pivot points, the first subset of coefficients, and the second subset of coefficients.