First time job

Source: Internet
Author: User

1-1: One of the basic questions about data compression is "what are we going to compress" and how do you understand that?

The signal from the source is represented by a minimum number of figures, which reduces the signal space that holds a given set of information or a collection of data samples.

That is, the compressed object refers to 1. Physical space, 2. Time interval, 3. Electromagnetic frequency band

1-2: Another basic problem with data compression is "Why compress", and how do you understand it?

Compressed into a file memory that can be reduced so that it can be easily passed. Improve its transmission, storage and processing efficiency.

1-6: How does data compression technology be categorized?

Data compression, is to use the least digital to represent the signal, divided into reversible compression and irreversible compression.

1: Reversible compression is also called distortion-free, error-free coding, noise-free coding-redundancy compression coding.

2: Irreversible compression is the distortion of the Code, information theory is called entropy compression

The understanding of them is: data redundancy can be compressed, compression can only be reversible within a certain limit, beyond a certain limit, the compression will be distorted; the greater the allowable distortion, the greater the compression limit can be.

Reference 1-4

1

A 497KB PDB format is compressed after 72KB

A 5500KB file is compressed after 4847KB

Different file types, the size of the file before compression and compressed file size is only different, and some files after compression change is not even change, and some files will be much smaller after compression.

2 Redundancy It represents the degree of the source information rate, and is a physical quantity that describes the objective statistical characteristics of the source. Can also be said to be from the excess of a volume, it does not affect the integrity of the data, it is precisely because of the existence of a surplus, to its source compression, compression will not affect the delivery of information. Source = information + redundancy. There is no way to quantify the redundancy of text that is excerpted from different sources, because the repetition is different for various information.

First time job

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.