A decoding device comprising: circuitry configured to receive coded data and a Supplemental Enhancement Information message specifying conversion information, the coded data pertaining to an image having luminance in a first dynamic range and the conversion information pertaining to a conversion of dynamic range of the luminance of the image from the first dynamic range into a second dynamic range; decode the received coded data to generate the image having luminance in the first dynamic range; and convert the dynamic range of luminance of the image from the first dynamic range into the second dynamic range using the conversion information, wherein the conversion uses an approximation of a knee function, wherein the knee function includes a plurality of knee points connected to at least one straight line, and the conversion information includes a conversion persistence flag having a value of 1 or 0 which indicates whether or not the conversion information is applied to a plurality of images of a video in output order, wherein the conversion uses the approximation of the knee function to map the dynamic range of the luminance of the image from the first dynamic range into the second dynamic range, and wherein the conversion information includes pre-conversion information indicating positions of the plurality of knee points in the first dynamic range and post-conversion information indicating positions of the plurality of knee points in the second dynamic range, wherein the pre-conversion information and the post-conversion information further indicate a priority order of the knee points for use in the approximation of the knee function. circuitry configured to receive coded data and a Supplemental Enhancement Information message specifying conversion information, the coded data pertaining to an image having luminance in a first dynamic range and the conversion information pertaining to a conversion of dynamic range of the luminance of the image from the first dynamic range into a second dynamic range; decode the received coded data to generate the image having luminance in the first dynamic range; and convert the dynamic range of luminance of the image from the first dynamic range into the second dynamic range using the conversion information, wherein the conversion uses an approximation of a knee function, wherein the knee function includes a plurality of knee points connected to at least one straight line, and the conversion information includes a conversion persistence flag having a value of 1 or 0 which indicates whether or not the conversion information is applied to a plurality of images of a video in output order, wherein the conversion uses the approximation of the knee function to map the dynamic range of the luminance of the image from the first dynamic range into the second dynamic range, and wherein the conversion information includes pre-conversion information indicating positions of the plurality of knee points in the first dynamic range and post-conversion information indicating positions of the plurality of knee points in the second dynamic range, wherein the pre-conversion information and the post-conversion information further indicate a priority order of the knee points for use in the approximation of the knee function.