Data compression first time job

---restore content starts---

1.

1-1 I personally understand "what we want to compress" in data compression:

A: Data is a very broad concept, so data compression is not only compressed numbers, but also the need for files, images, graphics, text, video, audio and so on compression.

1-2 "Why do you want to compress":

A: Data compression is to reduce the data storage space, so that high transmission, in storage and processing more convenient.

1-6 "How to classify data compression technology":

A: The compression of data is actually an encoding process, that is, the original data encoding compression. Therefore, the data compression method is also called the encoding method.

The compression method can be divided into two categories according to whether the decoded data is completely consistent with the original data: distortion coding (irreversible compression, information theory also known as entropy compression) and distortion-free coding (reversible compression).

2.

1. Use the compression tool on your computer to compress the different files. Investigate the effect of the size and type of the original file on the ratio of the compressed file to the original file size.

A: I used the picture (. jpg format, 858KB), the document (. doc format, 58KB) and the file (. pdf format, 149MB) were compressed, the results are: 857KB,19.9KB,126MB, by the results can be learned: different size, Different types of original files have different effects on the ratio of compressed files to the original file size.

2. Extract a few paragraphs from a popular magazine and delete any text that does not affect your understanding. For example, after deleting is, the, and that, and to my friend, the same meaning can still be passed in "This is the dog," belong. Measure the redundancy in the text with the ratio of the number of words deleted to the total number of words in the original text. Repeat the experiment with the words in a technical journal. Can we make a quantitative discussion of the redundancy of text that is excerpted from different sources?

a : For text that is excerpted from different sources, the repetition is not the same, some words are repeated several times, but some words appear infrequently. Therefore, we can not make a quantitative discussion of its redundancy.

Data compression first time job