Mode-dependent coefficient scanning and directional transforms for different colour sampling formats

A data decoding method comprising:

• detecting from parameters of a received bitstream whether intra prediction is enabled in the data and for detecting an intra-prediction mode for a block of samples represented in the bitstream;
• determining a scan pattern from a plurality of scan patterns for scanning frequency coefficients, the determined scan pattern being associated with the intra-prediction mode by a mapping, the mapping being different for chrominance and luminance samples, the chrominance and luminance samples being arranged in blocks, the blocks of chrominance samples having a different aspect ratio relative to the blocks of luminance samples, the blocks of chrominance samples having an aspect ratio in which a height is different than a width, and the intra-prediction mode associated with the determined scan pattern being determined in accordance with the aspect ratio such that the intra-prediction mode is remapped from a first intra-prediction mode to a second intra-prediction mode based on the aspect ratio;
• scanning the frequency coefficients representing the blocks of chrominance samples and the blocks of luminance samples in an order of the determined scan pattern which depends on the intra-prediction mode;
• and
• decoding video data for output.

A non-transitory computer-readable storage medium storing computer-readable instructions that, when executed by a computer, cause the computer to perform a method comprising:

• detecting from parameters of a received bitstream whether intra prediction is enabled in data and for detecting an intra-prediction mode for a block of samples represented in the bitstream;
• determining a scan pattern from a plurality of scan patterns for scanning frequency coefficients, the determined scan pattern being associated with the intra-prediction mode by a mapping, the mapping being different for chrominance and luminance samples, the chrominance and luminance samples being arranged in blocks, the blocks of chrominance samples having a different aspect ratio relative to the blocks of luminance samples, the blocks of chrominance samples having an aspect ratio in which a height is different than a width, and the intra-prediction mode associated with the determined scan pattern being determined in accordance with the aspect ratio such that the intra-prediction mode is remapped from a first intra-prediction mode to a second intra-prediction mode based on the aspect ratio;
• scanning the frequency coefficients representing the blocks of chrominance samples and the blocks of luminance samples in an order of the determined scan pattern which depends on the intra-prediction mode associated with the determined scan pattern;
• and
• decoding video data for output.