Multi-level representation of reordered transform coefficients

摘要

Techniques and tools for encoding and decoding a block of frequency coefficients are presented. An encoder selects a scan order from multiple available scan orders and then applies the selected scan order to a two-dimensional matrix of transform coefficients, grouping non-zero values of the frequency coefficients together in a one-dimensional string. The encoder entropy encodes the one-dimensional string of coefficient values according to a multi-level nested set representation. In decoding, a decoder entropy decodes the one-dimensional string of coefficient values from the multi-level nested set representation. The decoder selects the scan order from among multiple available scan orders and then reorders the coefficients back into a two-dimensional matrix using the selected scan order.

主权项

1. A method of decoding video in a computing device that implements a video decoder, the method comprising:
receiving information indicating a scan order in a bit stream; selecting one of a plurality of scan orders based on the information indicating the scan order; receiving entropy coded frequency coefficients of a block in the bit stream; with the computing device that implements the video decoder, entropy decoding the entropy coded frequency coefficients of the block, the frequency coefficients having been encoded using a multi-level nested-set representation, wherein the entropy decoding the entropy coded frequency coefficients includes:
entropy decoding a first symbol and a second symbol at a first level of the multi-level nested-set representation, the first symbol representing a first set of one or more of the frequency coefficients as a summary representation at the first level of the multi-level nested-set representation;at a given level of the multi-level nested-set representation that is lower than the first level:
decoding plural symbols at the given level, each of the plural symbols at the given level representing a set of one or more of the frequency coefficients; andfor each of the plural symbols at the given level, determining whether to split the set for the symbol into plural subsets and, if so, decoding plural sub-symbols at a lower level of the multi-level nested-set representation, each of the plural sub-symbols at the lower level representing one of the plural subsets; and applying the selected scan order to reorder the frequency coefficients of the block.