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Confidentiality/date line: 13pt Arial Regular, white Maximum length: 1 line Information separated by vertical strokes, with two spaces on either side Disclaimer.

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Presentation on theme: "Confidentiality/date line: 13pt Arial Regular, white Maximum length: 1 line Information separated by vertical strokes, with two spaces on either side Disclaimer."— Presentation transcript:

1 Confidentiality/date line: 13pt Arial Regular, white Maximum length: 1 line Information separated by vertical strokes, with two spaces on either side Disclaimer information may also be appear in this area. Place flush left, aligned at bottom, 8-10pt Arial Regular, white Indications in green = Live content Indications in white = Edit in master Indications in blue = Locked elements Indications in black = Optional elements Copyright: 10pt Arial Regular, white Passage Two. Multimedia Conception

2 Training target: In this part , our target is to train your reading speed. You should pay more attention to” word group”. Treating a group of words as a whole unit is a short cut to save your time. We have underlined the word groups in some sentences , and the rest can be practiced by yourself. If there are some new words , you may cover the note area with a piece of paper and try to guess their meanings without looking them up in the dictionary.

3  Text  Multimedia: Multimedia is the combination of sound ( Audio ), graphics , animation , video and text within an application.

4 ..  Audio: Audio is referring to sound or to things which can be heard; usually , the human ear can hear a range of frequencies between around 20Hz ~ 20KHz.But some animals can hear higher frequencies.

5 .  Audio waves can be converted to digital form by an ADC ( Analog Digital Converter ).To represent this signal digitally , we can sample it everyΔT seconds , sampling more often is of no value.

6 .  Audio CDs are digital with a sampling rate of44 , 100sample/sec , enough to capture frequencies up to22 , 050Hz , which is good for people , bad for dogs.

7  Computers in software can easily process digitized sound. Virtually all professional sound recording and editing are digital nowadays. MIDI is a representation of many musical instruments now.

8 .  MIDI music: Musical Instrument Digital Interface abbreviates MIDI. It is the serial interface running at32.5kbps that connects electronic instruments; the MIDI interface can connect up to32different instruments and carries signals from a sequencer or computer that instructs the different instruments , such as a drum machine or synthesizer , to play notes together with instructions called control-change messages , which control the volume , pitch and type of instrument used.

9 .  NOTE: a MIDI interface does not carry sounds , rather it carries notes and instructions to change to different preset sounds; many PCs generate sounds from MIDI data on-board. There are two kinds of MIDI sound generation: FM synthesis simulates musical notes by modulating the frequency of a rectangular base carrier wave , whereas waveform synthesis uses digitized samples of the notes to produce a more realistic sound. MIDI also allows multiple different voices , or notes , to be played back simultaneously ( MPC requires an8-voice synthesizer , but studio-quality instruments can have up to32MIDI voices ).

10  Video: video can be divided into two patterns: analogical system and digital system.

11  1. Analogical system: To represent the two- dimensional image in front of it as a one- dimensional voltage as a function of time , the camera scans an electron beam rapidly across the image and slowly down it , recording the light intensity as it goes. The exact scanning parameters vary from country to country. The system used in North and South America and Japan has 525 scan lines , a horizontal to vertical aspect ratio of 4 ∶ 3 , and 30 frames/sec. The European system has 625 scan lines , the same aspect rate of 4 ∶ 3 , and 25 frames/sec.

12  2.Digital system: The simplest representation of digital video is a sequence of frames , each consisting of a rectangular grid of picture elements , or pixels. Each pixel can be a single bit , to represent either black or white. To use8bits per pixel to represent256gray levels. This schedule gives high-quality black-and-white video. For color video , good systems use8bits for each of the RGB colors. While using24bits per pixel limits the number of colors to about16million , the human eye cannot even distinguish so many colors , let alone more.

13  To produce the smooth motion , digital video , like analog video , must display at least 25 frames/sec. However , since good quality computer monitors often rescan the screen from images stored in memory at 75 times per second or more , interlacing is not needed and consequently is not normally used. Just repainting the same frame three times in a row is enough to eliminate flicker.

14  Data Compression: Transmitting multimedia material in uncompressed form is completely out of the question. The only method is that massive compression is possible. All compression systems require two algorithms: one for compressing the data at the source ( encoding ), and the other for decompressing it at the destination ( coding ).These algorithms have certain asymmetries , that is to say , a multimedia document will be encoded once but will be decoded thousands of times.

15  On the other hand , for the real-time multimedia , such as video conferencing , slow encoding is unacceptable. Encoding must happen on the fly in real time. A second asymmetry is that the encode/decode process need not be invertible , that is , when compressing a file , transmitting it , and then decompressing it. When the decoded output is not exactly equal to the original input , the system is said to be lossy. If the input and output are identical , the system is lossless. Lossy systems are important because accepting a small amount of information loss can give a huge payoff in terms of the compression ratio possible.

16  The MPEG ( Motion Picture Experts Group ) standards: These are the main algorithms used to compress video and have been international standards since1993.Because movies contain both images and sound , MPEG can compress both audio and video. The goal of MPEG-1 ( International Standard11172 ) was to produce video recorder-quality output ( 352×240for NTSC ) using a bit rate of1.2Mbps. At this lower resolution , MPEG-1can be transmitted over twisted pair transmission lines for modest distances.MPEG-1 is also used for storing movies on CD-ROM in CD-Video format.MPEG-2 ( International Standard13818 ) was originally designed for compressing broadcast quality video into4to6Mbps. MPEG-2was expanded to support higher resolutions , including HDTV. It is likely that in the long run MPEG-1will dominate for CD-ROM movies and MPEG-2will dominate for long-haul video transmission.

17  JPEG:JPEG stands for Joint Photographic Experts Group , which is also sometimes abbreviated JPG. An image-compression standard and file format that define a set of compression methods for high- quality images such as photographs , single video frames , or scanned pictures. JPEG does not work very well when compressing text , line art , or vector graphics. JPEG uses lossy compression methods that result in some loss of the original data. When you decompress the original image , you don’t get exactly the same image that you started with , although JPEG was specifically designed to discard information not easily detected by the human eye. JPEG can store24-bit color images in as many as16million colors; files in Graphics Interchange Format ( GIF ) form can only store 256colors.

18 .  The End


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