Method and system for backward compatible, extended dynamic range encoding of video
In some embodiments, an encoding method for generating an extended dynamic range (EDR) channel in response to an input video channel, such that the EDR channel's code values consist of code values in a range from a standard black level, X, through a standard white level, Z, and an additional code value set. The EDR channel is displayable with standard dynamic range and standard precision by a standard dynamic range video system which maps to the level, X, any of the EDR channel's values less than X, and maps to the level, Z, any of the EDR channel's values greater than Z, and is displayable with an extended dynamic range greater than the standard dynamic range and/or a precision greater than the standard precision by an EDR video system. Other aspects are systems configured to perform embodiments of the encoding method, and methods and systems for displaying EDR video.
1. An encoding method, including a step of:
generating an extended dynamic range (EDR) channel in response to an input video channel, such that the EDR channel's code values consist of a set of N-bit, standard code values in a range from a standard black level, X, through a standard white level, Z, where 1<X and Z<(2 N −2), and an additional code value set, wherein the EDR channel is displayable with a standard dynamic range and a standard precision by a standard dynamic range (SDR) video system which maps to the black level, X, any of the EDR channel's code values in the range from Min to X, and maps to the white level, Z, any of the EDR channel's code values in the range from Z to Max, where Min is a value satisfying 1≦Min<X and Max is a value satisfying Z>Max, wherein the EDR channel is also displayable, with at least one of an extended dynamic range greater than the standard dynamic range and a precision greater than the standard precision, by an EDR video system, wherein the input video channel is indicative of at least one image having highlights, and the EDR channel's code values greater than the standard white level, Z, are indicative of the highlights, wherein N=8, and wherein the step of generating the EDR channel in response to the input video channels includes steps of:
applying inverse gamma encoding to values of the input video channel to generate EDR channel code values in a range from 16 through 235; and
applying log encoding to values of the input video channel to generate EDR channel code values in a range extension from 236 through 254.
2. An encoding method, including a step of:
generating an extended dynamic range (EDR) channel in response to an input video channel, such that the EDR channel's code values consist of a set of N-bit, standard code values in a range from a standard black level, X, through a standard white level, Z, where 1<X and Z<(2 N −2), and an additional code value set, wherein the EDR channel is displayable with a standard dynamic range and a standard precision by a standard dynamic range (SDR) video system which maps to the black level, X, any of the EDR channel's code values in the range from Min to X, and maps to the white level, Z, any of the EDR channel's code values in the range from Z to Max, where Min is a value satisfying 1≦Min<X and Max is a value satisfying Z>Max, wherein the EDR channel is also displayable, with at least one of an extended dynamic range greater than the standard dynamic range and a precision greater than the standard precision, by an EDR video system, and wherein the input video channel is indicative of at least one image having highlights, and the EDR channel's code values greater than the standard white level, Z, are indicative of the highlights, and wherein the step of generating the EDR channel in response to the input video channel includes steps of:
applying inverse gamma encoding to values of the input video channel to generate EDR channel code values in the range from the standard black level, X, to the standard white level, Z; and
applying log encoding to values of the input video channel to generate EDR channel code values in a range extension from the standard white level, Z, through Max.
3. The method of claim 2 , also including a step of asserting the EDR channel and metadata to a delivery system, wherein the metadata is indicative of at least one parameter of at least one of the inverse gamma encoding and the log encoding.
4. The method of claim 2 , wherein the EDR channel code values in the range extension from the standard white level, Z, through Max provide a dynamic range extension on the order of 1000 cd/m 2 , wherein the dynamic range extension is the difference between the extended dynamic range and the standard dynamic range.
5. An encoding method, including a step of:
generating an extended dynamic range (EDR) channel in response to an input video channel, such that the EDR channel's code values consist of a set of N-bit, standard code values in a range from a standard black level, X, through a standard white level, Z, where 1<X and Z<(2 N −2), and an additional code value set, wherein the EDR channel is displayable with a standard dynamic range and a standard precision by a standard dynamic range (SDR) video system which maps to the black level, X, any of the EDR channel's code values in the range from Min to X, and maps to the white level, Z, any of the EDR channel's code values in the range from Z to Max, where Min is a value satisfying 1≦Min<X and Max is a value satisfying Z>Max, wherein the EDR channel is also displayable, with at least one of an extended dynamic range greater than the standard dynamic range and a precision greater than the standard precision, by an EDR video system, wherein the input video is indicative of at least one image having highlights, and the EDR channel's code values greater than the standard white level, Z, are indicative of the highlights, and wherein the step of generating the EDR channel in response to the input video channel includes steps of:
mapping input video channel values that exceed a threshold value to EDR channel code values in the range from Z through Max in accordance with a first transfer function;
mapping input video channel values that do not exceed the threshold value to EDR channel code values that do not exceed Z in accordance with a second transfer function, wherein the second transfer function is steeper than the first transfer function, wherein N=8, and the threshold value is a value of the input video channel that is mapped to the EDR channel code value 235;
applying inverse gamma encoding to values of the input video channel to generate EDR channel code values in a range from 16 through 235; and
applying log encoding to values of the input video channel to generate EDR channel code values in a range extension from 236 through 254.
6. The method of claim 5 , wherein the EDR channel code values in the range extension from 236 through 254 provide a dynamic range extension on the order of 1000 cd/m 2 , wherein the dynamic range extension is the difference between the extended dynamic range and the standard dynamic range.
7. An encoding method, including a step of:
generating an extended dynamic range (EDR) channel in response to an input video channel, such that the EDR channel's code values consist of a set of N-bit, standard code values in a range from a standard black level, X, through a standard white level, Z, where 1<X and Z<(2 N −2), and an additional code value set, wherein the EDR channel is displayable with a standard dynamic range and a standard precision by a standard dynamic range (SDR) video system which maps to the black level, X, any of the EDR channel's code values in the range from Min to X, and maps to the white level, Z, any of the EDR channel's code values in the range from Z to Max, where Min is a value satisfying 1≦Min<X and Max is a value satisfying Z>Max, wherein the EDR channel is also displayable, with at least one of an extended dynamic range greater than the standard dynamic range and a precision greater than the standard precision, by an EDR video system, wherein the step of generating the EDR channel in response to the input video channel includes a step of:
mapping input video channel values that are less than a threshold value to EDR channel code values in the range from 1 to L, so that the EDR channel is displayable, with a precision greater than the standard precision, by the EDR video system, wherein L is an integer greater than the standard black level, X, and the threshold value is the input video value that is mapped to the EDR channel code value L, wherein L=2W, where W is an integer, and wherein N=8, X=16, and L=2W=32.