how does text compression work

It uses 64 different equations, but most of these don’t get used. Unlike with text where you can have lossless compression, and no data is lost, with images we have what’s called “Lossy Compression” where you do lose some data. Compression Why compress files? For now, we’re going to talk about the methods that are generally used to compress images, which will explain why some of them take up s… Here’s the result. How LZ77 Data Compression Works. You might not need to hear the creaking of the guitar pick on the string if the actual guitar is much, much louder. Necessary when the source data is not plain text, say audio or video data. In reality, LZ77 doesn’t use a list of keys, but instead replaces the second and third occurrence with a link back in memory: So now, when it gets to (h), it will look back to “howtogeek” and read that instead. If you’re interested in a more detailed explanation, this video from Computerphile is pretty helpful. For example, the word “the” would be compressed even when it appears in words like “there,” “their,” and “then.” With repeated text, you can get some crazy compression ratios. While all compression programs of this sort work with the same basic idea, there is actually a good deal of variation in the manner of execution. All Rights Reserved. This gives JPEGs an insanely high compression ratio, which can reduce a file that would be multiple megabytes down to a couple of kilobytes, depending on the quality. You really can't throw anything out without severely harming the final product. For comparison, here’s a 50% quality JPEG, which is nearly indistinguishable from the source PNG image unless you blow it up and take a close look. We use something called “interframe compression,” which calculates the changes between each frame and only stores those. Multidisciplinary software engineer. A language like Chinese might be a little harder to compress than English, for example. How LZ77 Data Compression Works by@dbudhrani. Video and audio compression works very differently. Most images store a list of numbers, with each number representing a single pixel. Lossy file compression. In this post we are going to explore LZ77, a lossless data-compression algorithm created by Lempel and Ziv in 1977. Video and audio compression works very differently. How-To Geek is where you turn when you want experts to explain technology. We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. Various lossless standards exist: PDF allows lossless compression of text documents This is mainly used for text and spreadsheets because losing words or data from a document isn't something you want to happen. When a request is made by a browser for a page from your site your webserver returns the smaller compressed file if the browser indicates that it understands the compression. There are different methods, each with a unique approach to a common problem, and each approach being used in different algorithms to reach a similar conclusion. Here’s an example. For example, text files can be smooshed down to become quite small. You’d think that they would just compress each frame of video using JPEG, and they certainly do that, but there’s a better method for video. In reality, most text is compressed with keys as small as just a few characters. The one on the left is at 3Mb/s, and the one on the right is 100Mb/s. That’s nearly 95% compression. How Does It Work? Some people swear by FLAC’s perfect audio quality, but with the prevalence of MP3, it seems most people either can’t tell or don’t mind the difference. Compression, however, isn’t a magic lozenge for curing a cramped hard drive.

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stu 30, 2020