Indexed Compression for Random Access Decompression

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Solution Overview

Problem

Conventional compression methods require decompression to start at the beginning of the data or at large intervals, limiting random access to compressed data.

Innovation Solution

An index correlating positions within uncompressed and compressed data is used to allow decompression to begin at any point, enabling direct reconstruction of arbitrary portions of uncompressed data without decompressing prior portions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional compression methods are used, then data can be compressed to use fewer bits, but decompression must start at the beginning of the data or at large intervals, limiting random access

Engineering Contradiction:

Improvedata sizeVSAvoidrandom access capability

Core Design Contradiction:

Quantity of substanceVSEase of operation

Solution Approach 1:

An index structure is pre-computed and stored alongside the compressed data, containing mappings from uncompressed byte positions to compressed data positions. This preliminary action enables direct random access during decompression without requiring sequential processing from the beginning, as the index provides direct lookup paths to any desired position in the uncompressed data

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The index acts as an intermediary data structure that bridges the compressed and uncompressed domains. It contains entries that map uncompressed byte addresses to corresponding compressed data positions, allowing the decompression process to jump directly to any position in the uncompressed data by looking up the index, rather than sequentially processing from the start

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If decompression starts at the beginning of compressed data, then arbitrary portions can be reconstructed, but time and processing power are wasted on unnecessary prior portions

Engineering Contradiction:

Improvedata reconstruction accuracyVSAvoiddecompression time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The index structure extracts and stores the essential positional mapping information separately from the compressed data. This extracted index contains only the necessary information (uncompressed byte position to compressed position mappings) needed for direct access, allowing the decompression process to skip unnecessary portions and extract only the specific data needed, thereby reducing time and processing power waste

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentEP4154406B1Compression/decompression using index correlating uncompressed/compressed content

Publication Date: 2025.07.09 MICROSOFT TECHNOLOGY LICENSING LLC

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AI summary

Compression of data that permits direct reconstruction of arbitrary portions of the uncompressed data. Also, the direct reconstruction of arbitrary portions of the uncompressed data. Conventional compression is done such that decompression has to begin either at the very beginning of the data, or at particular intervals (e.g., at block boundaries - every 64 kilobytes) within the data. However, the principles described herein permit decompression to begin at any point within the compressed data, without having to decompress any prior portion of the file. Thus, the principles described herein permit random access of the compressed data. In accordance with the principles described herein, this is accomplished by using an index that correlates positions within the uncompressed data with positions within the compressed data.