Intra prediction method and device and computer-readable storage medium

A method for intra prediction, applied to an encoder, the method comprising:

• determining at least one neighbouring block of a current block;
• determining a first intra prediction mode index of the at least one neighbouring block;
• constructing an intra prediction mode list corresponding to the current block based on the first intra prediction mode index of the at least one neighbouring block;
• determining a first intra prediction mode index of the current block based on the intra prediction mode list;
• obtaining a width to height ratio of the current block, and mapping, according to the width to height ratio, the first intra prediction mode index of the current block to a second intra prediction mode index in a wide-angle intra prediction mode;
• performing prediction for the current block based on a target intra prediction mode corresponding to the second intra prediction mode index of the current block, and obtaining a prediction block;
• wherein the step of mapping, according to the width to height ratio, the first intra prediction mode index of the current block to a second intra prediction mode index in a wide-angle intra prediction mode comprises:
• in case that width of the current block is greater than height of the current block and width to height ratio is greater than or equal to 2, determining the second intra prediction mode index based on the following table:
• the width to
• first intra prediction
• second intra prediction
• height ratio
• mode indices
• mode indices
• W/H == 2
• 2, 3, 4, 5, 6, 7
• 67, 68, 69, 70, 71, 72
• W/H == 4
• 2 to 11
• 67 to 76
• W/H == 8
• 2 to 13
• 67 to 78
• W/H == 16
• 2 to 15
• 67 to 80
• in case that the height of the current block is greater than the width of the current block and height to width ratio is greater than or equal to 2, determining the second intra prediction mode index based on the following table:
• the height to
• first intra prediction
• second intra prediction
• width ratio
• mode indices
• mode indices
• H/W == 2
• 61, 62, 63, 64, 65, 66
• −6, −5, −4, −3, −2, −1
• H/W == 4
• 57 to 66
• −10 to −1
• H/W == 8
• 55 to 66
• −12 to −1
• H/W == 16
• 53 to 66
• −14 to −1
• wherein, in both tables, the first intra prediction mode indices are sequentially mapped to the second intra prediction mode indices one to one.

A decoder, comprising:

• a processor, a memory having stored therein intra prediction instructions executable by the processor, and a communication bus for connecting the processor and the memory, wherein the intra prediction instructions, when executed, cause the processor to:
• determine at least one neighbouring block of a current block;
• determine a first intra prediction mode index of the at least one neighbouring block;
• construct an intra prediction mode list corresponding to the current block based on the first intra prediction mode index of the at least one neighbouring block;
• determine a first intra prediction mode index of the current block based on the intra prediction mode list;
• obtain a width to height ratio of the current block, and mapping, according to the width to height ratio, the first intra prediction mode index of the current block to a second intra prediction mode index in a wide-angle intra prediction mode;
• perform prediction for the current block based on a target intra prediction mode corresponding to the second intra prediction mode index of the current block, and obtaining a prediction block;
• wherein when the intra prediction instructions are executed, the processor is caused to:
• in case that width of the current block is greater than height of the current block and width to height ratio is greater than or equal to 2, determine the second intra prediction mode index based on the following table:
• the width to height
• first intra prediction
• second intra prediction
• ratio
• mode indices
• mode indices
• W/H == 2
• 2, 3, 4, 5, 6, 7
• 67, 68, 69, 70, 71, 72
• W/H == 4
• 2 to 11
• 67 to 76
• W/H == 8
• 2 to 13
• 67 to 78
• W/H == 16
• 2 to 15
• 67 to 80
• in case that the height of the current block is greater than the width of the current block and height to width ratio is greater than or equal to 2, determine the second intra prediction based on the following table:
• the height to width
• first intra prediction
• second intra prediction
• ratio
• mode indices
• mode indices
• H/W == 2
• 61, 62, 63, 64, 65, 66
• −6, −5, −4, −3, −2, −1
• H/W == 4
• 57 to 66
• −10 to −1
• H/W == 8
• 55 to 66
• −12 to −1
• H/W == 16
• 53 to 66
• −14 to −1
• wherein, in both tables, the first intra prediction mode indices are sequentially mapped to the second intra prediction mode indices one to one.