Method and apparatus for encoding or decoding blocks of pixel

A device for processing a current block of pixels of an image using a palette mode, the palette mode using a current palette that comprises a set of entries associating respective entry indexes with corresponding pixel values, the device comprising:

• a prediction unit configured to
• select an entry from a first palette predictor as an entry of a second palette predictor the first palette predictor being used to predict entries of a second palette and the second palette predictor being used to predict one or more entries of the current palette, and select all the entries from the second palette as entries of the second palette predictor, said second palette being used to process a block of pixels immediately preceding the current block,
• wherein said prediction of entries of the second palette using the first palette predictor is based on flags, each flag defining whether or not a corresponding entry in the first palette predictor is selected as an entry in the second palette,
• wherein the prediction unit is configured to select the entry from the first palette predictor as an entry of the second palette predictor by determining if an entry of the first palette predictor has a corresponding flag that defines no selection of the entry as an entry in the second palette and, if so, select that entry of the first palette predictor to be included in the second palette predictor for predicting the current palette;
• and
• wherein the prediction unit is configured to predict one or more entries of the current palette using said second palette predictor.

A device for processing a current block of pixels of an image using a palette mode, the palette mode using a current palette that comprises a set of entries associating respective entry indexes with corresponding pixel values, the device having a processor and memory configured to:

• select an entry from a first palette predictor as an entry of a second palette predictor, the first palette predictor being used to predict entries of a second palette and the second palette predictor being used to predict one or more entries of the current palette;
• select all the entries from the second as entries of the second palette predictor, said second palette being used to process a block of pixels in the image immediately preceding the current block,
• wherein prediction of entries of the second palette using the first palette predictor is based on flags, each flag defining whether or not a corresponding entry in the first palette predictor is selected as an entry in the second palette, and
• wherein said selection of an entry from the first palette predictor as an entry of the second palette predictor comprises determining if an entry of the first palette predictor has a corresponding flag that defines no selection of the entry as an entry in the second palette and, if so, selecting that entry of the first palette predictor to be included in the second palette predictor;
• and
• predicting one or more entries of the current palette using said second palette predictor.

A device for encoding a sequence of digital images into a bitstream comprising a processor and memory configured to:

• select an entry from a first palette predictor as an entry of a second palette predictor the first palette predictor being used to predict entries of a second palette, and the second palette predictor being used to predict one or more entries of a current palette,
• select all the entries from the second palette as entries of the second palette predictor, said second palette being used to process a block of pixels immediately preceding a current block of pixels,
• wherein said prediction of entries of the second palette using the first palette predictor is based on flags, each flag defining whether or not a corresponding entry in the first palette predictor is selected as an entry in the second palette, and
• wherein said selection of an entry from the first palette predictor as an entry of the second palette predictor comprises determining if an entry of the first palette predictor has a corresponding flag that defines no selection of the entry as an entry in the second palette and, if so, selecting that entry of the first palette predictor to be included in the second palette predictor;
• and
• predicting one or more entries of the current palette using said second palette predictor.

A device for decoding a bitstream comprising a sequence of digital images comprising a processor and memory configured to:

• select an entry from a first palette predictor as an entry of a second palette predictor, the first palette predictor being used to predict entries of a second palette and the second palette predictor being used to predict entries of a current palette,
• select all the entries from the second palette as entries of the second palette predictor, said second palette being used to process a block of pixels in the image immediately preceding the current block,
• wherein prediction of entries of the second palette using the first palette predictor is based on flags, each flag defining whether or not a corresponding entry in the first palette predictor is selected as an entry in the second palette, and
• said selection of an entry from the first palette predictor as an entry of the second palette predictor includes determining if an entry of the first palette predictor corresponds to a flag that defines no selection of the entry as an entry in the second palette and, if so, selecting that entry of the first palette predictor to be included in the second palette predictor;
• and
• predicting one or more entries of the current palette using said second palette predictor.

A non-transitory computer-readable medium storing a program which, when executed by a microprocessor or computer system in a device for processing a current block of pixels of an image using a palette mode, the palette mode using a current palette that comprises a set of entries associating respective entry indexes with corresponding pixel values, causes the device to perform a method comprising:

• selecting an entry from a first palette predictor as an entry of a second palette predictor, the first palette predictor being used to predict entries of a second palette and the second palette predictor being used to predict one or more entries of the current palette;
• selecting all the entries from the second palette as entries of the second palette predictor, said second palette being used to process a block of pixels immediately preceding the current block,
• wherein prediction of entries of the second palette using the first palette predictor is based on flags, each flag defining whether or not a corresponding entry in the first palette predictor is selected as an entry in the second palette, and
• said selection of an entry from the first palette predictor as an entry of the second palette predictor comprises determining if an entry of the first palette predictor corresponds to a flag that defines no selection of the entry as an entry in the second palette and, if so, selecting that entry of the first palette predictor to be included in the second palette predictor;
• and
• predicting one or more entries of the current palette using said second palette predictor.