Implementation Issues
The nature of the data to be encoded influences the effectiveness of a particular compression algorithm. For example, in sending updates to the Google Chrome browser, a specialized algorithm is used based on knowledge of the archive and executable format.
Delta encoding performs best when data has small or constant variation; for an unsorted data set, there may be little to no compression possible with this method.
In delta encoded transmission over a network where only a single copy of the file is available at each end of the communication channel, special error control codes are used to detect which parts of the file have changed since its previous version. For example, rsync uses a rolling checksum algorithm based on Mark Adler's adler-32 checksum.
Read more about this topic: Delta Encoding
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