Speculative Huffman Decompression Using Overlapping Bit Windows
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Solution Overview
Problem
Huffman coding's variable length codewords result in compressed data that is not byte-aligned, making it difficult for decoders to determine the start and end of each codeword without decoding the previous codeword, leading to sequential decoding which is inefficient.
Innovation Solution
The proposed solution involves speculatively and concurrently detecting codewords in overlapping bit windows within the series of Huffman codewords, selecting valid codewords, and decompressing them to increase decoding speed, particularly applicable to decompressing data compressed using Huffman and LZ coding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Huffman coding with variable length codewords is used for compression, then compression ratio is improved, but decoding speed deteriorates due to sequential decoding requirement
Solution Approach 1:
The patent pre-calculates and stores the cumulative lengths of all possible codewords in a lookup table before decoding begins. This preliminary preparation allows the decoder to quickly determine codeword boundaries without sequential processing, thereby maintaining high compression ratios while significantly improving decoding speed through parallel processing capabilities
Solution Approach 2:
The patent transitions from one-dimensional sequential decoding to multi-dimensional parallel processing by examining multiple possible codeword positions simultaneously using overlapping bit windows. This dimensional shift enables the decoder to process multiple potential codeword starts in parallel, resolving the speed bottleneck while preserving compression efficiency
2Measurement precision
If sequential decoding is used to determine codeword boundaries, then decoding accuracy is maintained, but processing time increases
Solution Approach 1:
The patent pre-computes cumulative codeword lengths and stores them in a lookup table, allowing the decoder to verify potential codeword boundaries in constant time rather than sequentially. This preliminary preparation maintains accurate boundary detection while eliminating the time penalty of sequential processing
Solution Approach 2:
The patent uses feedback from the lookup table to validate potential codeword positions detected in parallel. By comparing detected positions against pre-calculated cumulative lengths, the system ensures accurate boundary detection while maintaining the speed benefits of parallel processing
Data Source
AI summary
A computing system includes a network interface, a processor, and a decompression circuit. In response to a compression request from the processor the decompression circuit compresses data to produce compressed data and transmits the compressed data through the network interface. In response to a decompression request from the processor for compressed data the decompression circuit retrieves the requested compressed data, speculatively detects codewords in each of a plurality of overlapping bit windows within the compressed data, selects valid codewords from some, but not all of the overlapping bit windows, decodes the selected valid codewords to generate decompressed data, and provides the decompressed data to the processor.