1. Although the information and data information and data are often used together, the concept is different and must be distinguished. The data is used to record and transmit information, or data is a carrier for information. Really useful is not the data itself, but the information carried by the data. During transmission information, a large amount of data processing is required. To this end, a large number of image data and voice data are saved and transmitted in the multimedia system, which is one of the most basic problems of multimedia technology and one of the biggest problems.
No matter which medium, they both carry certain information. According to the information of the founder, the information function is quantified by the viewpoint and method of probability theory, and the information function is:
I (ai) = - log2pi (i = 1, 2, 3 ..., r)
Among them, Pi (i = 1, 2, ..., r) indicates a random message set x: {A1, A2 ..., AR} Message AI (i = 1, 2, ..., r)'s prior probability. It can measure the amount of information contained in AI (i = 1, 2 ..., r). I (AI) (i = 1, 2 ..., r) statistical averages in X's probably probability space P: {P1, P2, ... PR}:
H (x) = h {p1, p2, ..., pr} =
-
Pilog2pi
The information entropy for x is used to measure the amount of theverage information contained in each message in X. Entropy, as an amount of information quantification, in contrast to entropy in thermodynamics (description system disorderly), and the amount of information is the extent of system order. 2, the amount of information of the information and the necessary digitized video, the amount of data such as media information such as audio is very large, and the following is the amount of information such as text, graphics, image, and audio, etc., calculate its data amount. .
(1) The resolution of the text is 768 × 512, the character size is 8 × 8 dot matrix, each character is represented by two bytes, the number of full screen characters is: (768/8) × (512 / 8) = 6144 (1) One screen text requires storage space (bytes): 6144 × (2 × 8) = 96kbit = 12kb (2) Dot matrix map with a simple full-screen point line, set screen The size is 768 × 512, each point is 256 colors, then the space required for a screen point pattern is: 768 × 512 × log2256 = 384KB (800 × 600 × 16/8 = 0.926MB complex computer color image usually It is obtained by the scanner. If you want to enter a 11-inch × 8.5-inch color photo into a computer, the resolution of the scanner is set to 300dpi (point / inches), each pixel R, G, B components are 8 respectively Bit, scanning is the 24-bit real color map, and the image after the scanner is digitally occupied by 25.245MB of storage space. (3) Vector graphical vector graphics is relatively small. For example, storage one The vector graphic consisting of 500 lines, that is, to store the line burst of the constructive graphic, each line can be represented by five items such as starting x, starting point Y, end point X, endpoint Y, attribute, where the attribute is The color and width of the finger, etc., the screen size is 768 × 512, the property bit is represented by 1 byte, then the storage space of each line is: 10 × 2 9 × 2 8 = 46bit stores such a graphic The required space is: 500 × 46 ≈ 2.3kb (4) Digital sound (voice) sound analog bandwidth is 4kHz, the sampling size is 8bit, the sampling frequency is 8 kHz, the space required to store LS is: 8 × 8 = 64kbit = 8kb (5) Digital high quality audio sound analog bandwidth is 22 kHz, the sampling size is 32bit, the sampling frequency is at least 44 kHz. The number of digitized audio needs such a storage LS is: 44 × 32 = 1408kbit = 176kb ( 6) Digital video PAL system Europe and China's color video image standard used in China, its video bandwidth is 5MHz, the frame rate is 25 frames / s, the sample width is 24bit, the frequency is at least 10MHz, and thus stores a digital PAL type video The space required for the image is: 10 ÷ 25 × 24 = 9.6Mbit = 1.2MB Store the space required for a second PAL system to: 1.2 × 25 = 30MB from the above multimedia information and data quantity, storage digitized The storage space required for multimedia information is very large. Require from data transmission, multimedia communication The system's processing and transmission of massive information is also limited by factors such as computer itself and transmission lines.
For example, a computer communication system, NISC video display screen is distinguished 720 × 480, 30 frames per second, the pixel of the screen is: 720 × 480 = 345600 one-screen image is generated by an odd row and an even-line scan, a total There are 240 singular rows and 240 or 240, if the 24-bit true color is used, the full screen of the NTSC system requires: 720 × (480/2) × 24 = 4147200bit To perform 30 frames per second The rate of 4147200 × 30 = 124416000 bit / s. Assuming that the data rate of the transfer channel is 7 Mbit / s, the required image compression factor is 18: 1. This needs to be compressed by the MPEG algorithm. It can be seen that one of the biggest problems faced by multimedia information is the problem of massive data, and data compression will be an important way to solve problems. 3. The data rate (uncompressed audio data rate (uncompressed) of the four levels of the bandwidth multimedia audio information is transmitted. Digital audio data rate
species
Sample rate / sample data rate (kb / s) phone 8864 conference 1614224 laser record (CD-AUDIO) 44.116705.6X2 Digital audio record (DAT) 4816768
Digital TV image data rate
Type spatial and temporal resolution data rate (KB / s) SIF352X240X307.603 CCIR720X576X2531.104HDTV1280X720X6055.296 SIF: Soruce Input Forrmat CCIR: Consulatative Committee International Radio HDTV: High Definition Television Format for digitized voice, video image and an audio signal high, due to the real-time Play, therefore also requires increased transmission band width between CPUs and memory, and the existence: >> Full color, full screen, full-motion high frequency image requires data transmission bandwidth of 300MB / s. >> High quality audio requires data transmission bandwidth to 176kb / s. >> Voice requires data transmission bandwidth to 8kb / s.
