Methods and devices for coding and decoding a data stream representative of at least one image.

A method for coding a data stream representative of at least one image, said image being split into blocks, the coding method being implemented by a coding device and comprising, for at least one block of the image, referred to as a current block:

• determining a group of pixel values in the block from previously decoded pixels, and
• for each pixel of the block:
• (i) determining a prediction value associated with the pixel according to a first prediction mode, according to which the pixel is predicted from at least one other previously decoded pixel, said other previously decoded pixel belonging to said current block,
• (ii) determining a prediction mode for the pixel from the first prediction mode and a second prediction mode according to which the pixel is predicted using a prediction resulting from said group of pixel values in the block,
• (iii) coding in the data stream an item of information indicating whether the pixel is predicted according to the second prediction mode,
• (iv) in response to the item of information indicating that the pixel is predicted according to the second prediction mode:
• (a) selecting a value of said group, and
• (b) replacing said prediction value associated with the pixel with said selected value,
• (v) calculating a quantized prediction residue associated with said pixel using the prediction value associated with the pixel and the value of said pixel,
• (vi) reconstructing said pixel using the prediction value associated with the pixel and the decoded prediction residue, and
• (vii) coding the quantized prediction residue associated with said pixel in the data stream.

A device for decoding a coded data stream representative of at least one image, said image being split into blocks, wherein the decoding device comprises:

• a processor configured, for at least one block of the image, referred to as a current block, to:
• determine a group of pixel values in the block from previously decoded pixels, and
• for each pixel of the block:
• (i) decode a prediction residue associated with said pixel,
• (ii) determine a prediction value associated with the pixel from at least one other previously decoded pixel, said other previously decoded pixel belonging to said current block,
• (iii) determine from the data stream an item of information indicating whether the pixel is predicted using a prediction resulting from said group of pixel values in the block,
• (iv) in response to the item of information indicating that the pixel is predicted using a prediction resulting from the group of pixel values in the block:
• (a) select a value of said group, and
• (b) replace said prediction value associated with the pixel with said selected value, and
• (v) reconstruct said pixel using the prediction value associated with the pixel and the prediction residue.

A device for coding a data stream representative of at least one image, said image being split into blocks, wherein the coding device comprises:

• a processor configured, for at least one block of the image, referred to as a current block, to:
• determine a group of pixel values in the block from previously decoded pixels, and for each pixel of the block:
• (i) determine a prediction value associated with the pixel according to a first prediction mode, according to which the pixel is predicted from at least one other previously decoded pixel, said other previously decoded pixel belonging to said current block,
• (ii) determine a prediction mode for the pixel from the first prediction mode and a second prediction mode according to which the pixel is predicted using a prediction resulting from said group of pixel values in the block,
• (iii) code in the data stream an item of information indicating whether the pixel is predicted according to the second prediction mode,
• (iv) in response to the item of information indicating that the pixel is predicted according to the second prediction mode:
• (a) select a value of said group, and
• (b) replace said prediction value associated with the pixel with said selected value,
• (v) calculate a prediction residue associated with said pixel using the prediction value associated with the pixel and the value of said pixel,
• (vi) code the prediction residue associated with the pixel in the data stream, and
• (vii) reconstruct said pixel using the prediction value associated with the pixel and the decoded prediction residue.

A non-transitory computer-readable data medium, comprising instructions of a computer program stored thereon which when executed by a processor of a decoding device configure the decoding device to decode a coded data stream representative of at least one image, said image being split into blocks, the decoding comprising, for at least one block of the image, referred to as a current block:

• determining a group of pixel values in the block from previously decoded pixels, and
• for each pixel of the block:
• (i) decoding a prediction residue associated with said pixel,
• (ii) determining a prediction value associated with the pixel according to a first prediction mode, according to which the pixel is predicted from at least one other previously decoded pixel, said other previously decoded pixel belonging to said current block,
• (iii) decoding from the data stream an item of information indicating whether the pixel is predicted according to a second prediction mode according to which the pixel is predicted using a prediction resulting from said group of pixel values in the block,
• (iv) in response to the item of information indicating that the pixel is predicted according to the second prediction mode:
• (a) selecting a value of said group, and
• (b) replacing said prediction value associated with the pixel with said selected value, and
• (v) reconstructing said pixel using the prediction value associated with the pixel and the prediction residue.

A non-transitory computer-readable data medium, comprising instructions of a computer program stored thereon which when executed by a processor of a coding device configure the coding device to code a data stream representative of at least one image, said image being split into blocks, the coding comprising, for at least one block of the image, referred to as a current block:

• determining a group of pixel values in the block from previously decoded pixels, and
• for each pixel of the block:
• (i) determining a prediction value associated with the pixel according to a first prediction mode, according to which the pixel is predicted from at least one other previously decoded pixel, said other previously decoded pixel belonging to said current block,
• (ii) determining a prediction mode for the pixel from the first prediction mode and a second prediction mode according to which the pixel is predicted using a prediction resulting from said group of pixel values in the block,
• (iii) coding in the data stream an item of information indicating whether the pixel is predicted according to the second prediction mode,
• (iv) in response to the item of information indicating that the pixel is predicted according to the second prediction mode:
• (a) selecting a value of said group, and
• (b) replacing said prediction value associated with the pixel with said selected value,
• (v) calculating a quantized prediction residue associated with said pixel using the prediction value associated with the pixel and the value of said pixel,
• (vi) reconstructing said pixel using the prediction value associated with the pixel and the decoded prediction residue, and
• (vii) coding the quantized prediction residue associated with said pixel in the data stream.