![]() Many publications on compressing television signals surfaced between the 1950s-1970s, and these eventually proved to be useful in other applications, most notably for the aerospace industry.įor example, various interplanetary spacecraft launched in the 1960s could record data faster than what they could transmit to earth. Before the invention of analog-to-digital converters and entropy coding methods in the 1950s, compaction of television signals required reducing the quality of the video before transmission, a technique that’s referred to as lossy compression. Since the invention of telegraphy, telephony, and especially television, engineers have sought ways to reduce the bandwidth required for transmitting electrical signals. – Aske Simon Christensen, author of Shrinkler and co-author of Crinkler. For executable compression in particular, where the sum of decompression code size and compressed size is what counts, the optimal balance between these two depends on the intended target size. Historyĭesigning a compression format requires trade-offs, such as compression ratio, compression speed, decompression speed, code complexity, code size, memory usage, etc. x86 assembly codes for some of algorithms discussed here may be found here. However, some decoders without sources for a compressor are also useful to show the conversion between architectures.ĭrop me an email, if you would like to provide feedback on this post. Considerations include an open-source compressor and the speed of compression and decompression. However, the priority for this post is exploring algorithms with the best ratios that also use the least amount of code possible for decompression. Many variations of LZ surfaced in the past thirty years, and a detailed description of them all would be quite useful for historical reference. In executable compression, we can consider LZ an umbrella term for LZ77, LZSS, LZB, LZH, LZARI, and any other algorithms inspired by those designs. The focus here will be on variations of the Lempel-Ziv (LZ) scheme published in 1977 that are suitable for resource-constrained environments such as 8, 16, and 32-bit home computers released in the 1980s. Except for research by Introspec about various 8-Bit algorithms on the ZX Spectrum, it’s tricky to find information in one location about compression used in Demoscene productions. My last post about compression inadvertently missed algorithms used by the Demoscene that I attempt to correct here. ![]() ![]() Lempel–Ziv–Oberhumer-Markov Algorithm (LZOMA).Recycling Compression Algorithms for the Z80, 8088, 6502, 8086, and 68K Architectures. ![]()
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