What are the two categories of data compression technologies?

Data compression technology is divided into two categories, with three divisions: 1. Instant compression and non-instant compression; 2. Data compression and file compression; 3. Lossless compression and lossy compression.

Data compression refers to reducing the amount of data to reduce storage space without losing useful information, improve its transmission, storage and processing efficiency, or according to A technical method that uses a certain algorithm to reorganize data and reduce data redundancy and storage space.

In computer science and information theory, data compression or source encoding is the process of representing information in fewer data bits (or other information-related units) according to a specific encoding mechanism than without encoding.

For example, if we encode "compression" as "comp" then this article can be represented with fewer data bits. A popular example of compression is the ZIP file format used by many computers. It not only provides compression functions, but also serves as an archive tool (Archiver) that can store many files into the same file.

Classification of data compression technology

There are many ways to compress data, and data with different characteristics have different data compression methods (that is, encoding Method)

Data compression technology is divided into two categories, with three classification methods:

1. Instant compression and non-instant compression

For example, making an IP phone call means converting the voice signal into a digital signal, compressing it at the same time, and then transmitting it through the Internet. This data compression process is carried out in real time. Real-time compression is generally used in the transmission of video and audio data. Instant compression often uses specialized hardware devices, such as compression cards.

Non-real-time compression is often used by computer users. This kind of compression is only performed when needed and has no real-time nature. For example, compress a picture, an article, a piece of music, etc. Non-instant compression generally does not require special equipment, just install and use the corresponding compression software directly on the computer.

2. Data compression and file compression

In fact, data compression includes file compression. Data originally refers to any digital information, including various types of information used in computers. It is a kind of file, but sometimes, data refers specifically to some temporal data, which are often collected, processed or transmitted in real time. File compression refers specifically to the compression of data to be stored in physical media such as disks, such as the compression of an article data, a piece of music data, a piece of program encoding data, etc.

3. Lossless compression and lossy compression

Lossless compression uses the statistical redundancy of data to compress. The theoretical limit of data statistical redundancy is 2:1 to 5:1, so the compression ratio of lossless compression is generally lower. This type of method is widely used in the compression of text data, programs and image data in special applications that require accurate storage of data.

The lossy compression method takes advantage of the fact that human vision and hearing are insensitive to certain frequency components in images and sounds, allowing a certain amount of information to be lost during the compression process. Although the original data cannot be completely restored, the lost part has less impact on understanding the original image, but in exchange for a larger compression ratio.

Lossy compression is widely used in the compression of voice, image and video data.

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