Method for encoding/decoding a picture block
A method and device for encoding or decoding a picture block having a luminance component. The method includes obtaining a luminance residual block (L r ) by subtracting a first representation (L l , L lD ) of an average value of the luminance component calculated from the luminance component, obtaining a second representation (ƒ(L l ), ƒ(L l ) D ) of the average value by applying a transfer function to the average value (L l ) of the luminance component in order to reduce the dynamic range of the average value and encoding a luminance block (L e ) obtained by adding ( 105, 302 ) together the luminance residual block (L r ) and the second representation (ƒ(L l ), ƒ(L l ) D ) of the average value.
1. A method for encoding a picture block, said picture block comprising a plurality of pixels, each pixel having a luminance component, wherein the method comprises:
obtaining a luminance residual block by subtracting a first representation of an average value of the luminance component from the luminance component, said average value of the luminance component being the average of each value of said luminance component of the plurality of pixels of the picture block;
obtaining a second representation of the average value by applying a transfer function to the average value of the luminance component in order to reduce the dynamic range of the average value;
encoding a luminance block obtained by adding together the luminance residual block and the second representation of the average value.
2. A method for decoding a picture block, said picture block comprising a plurality of pixels, each pixel having a luminance component expressed in an original number of bits, wherein the method comprises:
obtaining a luminance residual block by subtracting an average value of a luminance block from said luminance block, said average value of the luminance component being the average of each value of said luminance component of the plurality of pixels of the picture block;
obtaining a decoded luminance component of the picture block by adding together the luminance residual block and a representation, expressed in the original number of bits, of the average value of the luminance block.
3. A device of encoding a picture block, said picture block comprising a plurality of pixels, each pixel having a luminance component, wherein the device comprises a processor configured to:
obtain a luminance residual block by subtracting a first representation of an average value of the luminance component from the luminance component, said average value of the luminance component being the average of each value of said luminance component of the plurality of pixels of the picture block;
obtain a second representation of the average value by applying a transfer function to the average value of the luminance component in order to reduce the dynamic range of the average value;
encode a luminance block obtained by adding together the luminance residual block and the second representation of the average value.
4. A device of decoding a picture block, said picture block comprising a plurality of pixels, each pixel having a luminance component expressed in an original number of bits, the device comprises a processor configured to:
obtain a luminance residual block by subtracting an average value of a luminance block from said luminance block, said average value of the luminance component being the average of each value of said luminance component of the plurality of pixels of the picture block;
obtain a decoded luminance component of the picture block by adding together the luminance residual block and a representation, expressed in the original number of bits, of the average value of the luminance block.