Chapter 1 Multimedia Technology Introduction
Difficulty analysis:
· Multimedia concept
To understand the concept of multimedia, first talk from the media. The media typically has two meanings in the computer domain: one refers to the entity stored information, such as a disk, an optical disk, a tape, a semiconductor memory, and the like; the second is a carrier that transmits information, such as numbers, text, sound, graphics, and images. The media in multimedia technology can be seen is the latter.
The so-called "multimedia" is "a combination of various media" from literal understanding, and related techniques are "how to conduct a variety of media integrated technology." We generally believe that "multimedia" refers to technologies that can be acquired, handled, edit, store, and demonstrate more than two different types of information media (eg text, sound, graphics, images, animations, videos, etc.). It can be seen that "multimedia" that we often say is finally concatenated as a "technology", often not referring to a variety of media itself, mainly refers to a complete set of techniques for processing and applying it.
Chapter II Representation of Multimedia Information
Difficulty analysis:
· MIDI's meaning, comparison of MIDI and digital sound
MIDI is an English abbreviation of the instrument digital interface, which is an international standard of digital music, which is a product combined with a computer. The MIDI information is actually a numeric description of the score, where the score is completely consisting of a musical instrument sequence, timing, and instrument definitions called synthetic tone. When a set of MIDI messages play through the music synthesizer chip, the synthesizer explains these symbols and generates music.
Select MIDI or digital sound, consider the ability of the computer to process digital files, the ability to play back hardware and whether there is a language dialogue.
· Bitchart image, comparison of vector graphics
Bit-Map Image refers to an image that has been discretized on space and brightness. A bitmap image is usually taken into account as a matrix, one element (pixel) in the matrix corresponds to one point of the image, and the corresponding value represents the grayscale or color level of the point.
Vector graphics (Vector-based Image) is described in a collection of instructions. These instructions are used to describe various attributes and parameters such as the shape, position, color of the figure.
Vector diagraph compares to bitmaps, mainly watching space and performance, generally, to see the complexity of the image, simple graph to use vector diagram to describe some, complex map Using bitmaps.
· Comparison of waveform sounds and MIDI music
The MIDI message is actually the figure of the score. Compared to the waveform sound, MIDI data is not a sound but instruction, so its data is much less than the waveform. For example, 30 minutes of stereo high quality music, with a waveform file without compression recording, about 300MB of storage space; and the same MIDI data, only 200KB, both of which differ from 1500 times. In addition, the editing of MIDI is flexible, and attributes such as tunes, tones, etc. can be freely changed, and the waveform sound is difficult to do.
The waveform sound is independent of the device, and the MIDI data is related to the device, that is, the sound generated by the MIDI music file is related to a particular MIDI device used to play back. In general, the most important advantage of digitized sound is the consistency of playback quality, and the reliability is better, and the quality of the final guarantees, while MIDI is relatively poor.
· The relationship between waveform sound quality and data volume
The sound card for sound cards can be measured by three basic parameters, namely the sampling frequency, the number of sampling bits, and the number of channels.
Sampling frequencies refer to the number of sampling within the unit time. The larger the sampling frequency, the smaller the interval between the sampling points, the more true the sound obtained after digitization, the greater the corresponding amount of data. Sound cards generally provide three different sampling frequencies 11.025kHz, 22.05kHz and 44.1kHz.
The number of samples is the number of bits that record the size of the sample value per sampling value. The number of sampling sites usually have two kinds of 8bits or 16bits. The larger the sampling position, the more delicate the length of the sound can be recorded, the greater the corresponding amount of data.
The number of channels used means that the sound processed is mono or stereo. The mono is only single data stream during sound processing, and the stereo requires two data streams of the left and right channels. Obviously, the effect of stereo is good, but the corresponding amount of data is doubled than the amount of data of the mono. · Image and graphical file format
In computer science, both concepts of graphics and images are different: graphics generally refer to screens, such as lines, circles, arcs, arbitrary curves and graphics, etc .; the image refers to the actual situation captured by the input device. Scene screens or any screen stored in digital form.
The images are composed of some pixels that are ranked, and the storage formats in the computer are BMP, PCX, TIF, GIFD, etc., general data volume is large. In addition to expressing real photos, it can also show certain details of complex paintings and have flexible and creative features.
Unlike the image file, only the algorithm of the generated diagram and some feature points on the graph are recorded in the graphical file, also known as vector. At the time of the computer restore output, the adjacent feature points form a curve with a small number of small linear connections, and if the curve is a closed graph, it can also fill the color by coloring algorithm. Its maximum advantage is that transformations such as moving, scaling, rotation, and twisted, mainly used to represent wireframe type drawings, engineering drawings, art characters, etc. Common vector graphics files have 3DS (for 3D modeling), DXF (for CAD), WMF (for desktop publishing), etc. The graphics only save algorithms and feature points, so the storage space it occupies is smaller than the large amount of data of the bitmap. However, since each screen is displayed, it needs to be recalculated, so there is no image if the display speed is fast. In addition, when printing output and amplification, the quality of graphics is high and distortion occurs often.
· What is the difference between animation and video?
Animation and video information is a static image or graphic sequence of continuous gradients, which is sequentially replaced along the time axis, thereby constituting a medium of motion visual. When each frame image is generated by manual or computer, we often refer to an animation; when each frame image is in real time, we often refer to video video, or referred to as a video .
Chapter 3 Compression of Multimedia Information
Difficulty analysis:
· Huffman Code
Huffman coding reflects the idea of statistical coding. It is represented by a large number of symbols that appear frequently with a small number of bits, and for more frequent symbols, more bits are used. Its coding efficiency depends primarily on the probability distribution that needs to be encoded, the higher the compression ratio, the higher the compression ratio. Its encoding process see the textbook 41.
· Arithmetic coding, predictive coding, transformation coding, model coding principle
The arithmetic coding is also a statistical code, each symbol corresponding to a sub-zone of 0 to 1, and the interval length is the probability of the symbol. This method will represent the encoded symbol string (numerical string) to a range between the real numbers 0 to 1. Initially set it to the entire interval. When a new range to be encoded, first map the complete 0 to 1 interval to the previously formed interval, and then the new range is reflected as the new symbol corresponding section of the new symbol on 0 to 1. When decoding, the original symbol string is solved one by one based on the coverage of the interval.
The predicting code is predicted by a new sample value based on a data model using a conventional sample value, and then encodes the sample actual value to the difference value of the predicted value. If the model is good enough, and the time dependence of the sample sequence is strong, the amplitude of the error signal will be much smaller than the original signal, and the difference can be quantified by a small value to obtain a better compression effect. The predicting coding is commonly used is differential pulse coding modulation (DPCM) and adaptive differential pulse coding modulation (ADPCM).
The transformation coding is an image signal that will typically describe in the spatial domain, and transforms to another orthogonal vector space (ie the transform domain) to describe, and the correlation between the signal components described in the transform domain by selecting the appropriate transformation relationship Small or unrelated to each other, thereby achieving the purpose of data compression.
Model coding refers to the method of parameter estimation of the transmitted image. Typical fractal coding. · Briefly describe the main differences between MPEG and JPEG.
MPEG video compression technology is a data compression technology for moving images. In order to improve the compression ratio, intra image data and inter preamload data compression techniques must be used simultaneously.
MPEG effectively compresses the number of bits of data by frame motion compensation, which uses three images, intra-frame, predicted graphs, and two-way predicted graphs. Effectively reduces redundant information. For MPEG, inter-frame data compression, motion compensation, and bidirectional prediction, this is the main difference between JPEG. The same places in JPEG and MPEG use DCT intra image data compression coding.
Further, the MPEG in the MPEG signal includes different contents such as still screen (intra-frame) and motion information (inter predictive graph), and the quantizer is more important than the design consideration of the design of the JPEG compression algorithm.
· About compression ratio
Measuring a standard for a compression algorithm, in addition to the decompressed data, it is the size of the compression ratio. There are two types of compression than commonly used:
(1) Sampling compression ratio
Sampling compression ratio = total sample number of total sampled / compressed output before compression
Since the signals in the computer are digital signals, some information is usually to be decompressed. Therefore, the bit compression ratio below is more practical.
(2) Bit compression ratio
Bit compression ratio = total bits of the total bits / compression output before compression
Regardless of which definition is used to calculate the compression ratio, it is apparent that both definitions reflect the ratio of the compressed proximal compression data.
· Digital video system
Like the movie, digital video is also composed of a sequence still picture, which is referred to as a frame. In general, the frame rate is selected between 24 and 30 frames per second, and the motion of the video is very smooth; while 15 frames per second, the continuous moving video will have a feeling of pause.
my country's TV standards are PAL system, which specifies a video per second, 625 scan per frame. The number of valid lines used in the 625 line for scanning images is only 576 lines, so the resolution of the image in the vertical direction is 576 points. According to the current 4: 3 (width: height) TV standard, the resolution of the image in the horizontal direction should be 576 * 4/3 = 768, which has obtained the common image size of 768 * 576.
For another common digital video format NTSC, it specifies 30 frames per second, 525 per frame, and the interlaced scan mode is equipped, each frame consists of two fields, and its image size is 720 * 486. Because the PAL system is different from NTSC, the frequency and color processing methods are different, both are incompatible with each other.
· Factors affecting digital video quality
Five important technical parameters in multimedia digital video will eventually affect the quality of video images, which are frame speed, resolution, color number, compression ratio, and keyframes.
(1) Frame speed: Commonly used 25 frames / sec (PAL), 30 frames / sec (NTSC). The higher the frame speed, the greater the amount of data, the better the quality.
(2) Resolution: The larger the video resolution, the larger the amount of data, the better quality. Here you should pay attention to distinguish between video resolution and video display resolution (number of pixel points displayed).
(3) Color number: Refers the number of colors that can be used in the video. The more color digits, the more true color, the greater the amount of data.
(4) Compression ratio: Compression ratio does not have much impact on image quality, and after more than a factor, it will clearly see the image quality decrease, and the compression ratio takes a larger time to decompress the time.
(5) Keyframe: Video data has strong inter-inter-frame correlation, dynamic video compression is characterized by inter-frame correlation, by dynamic synthesizing intermediate video frames throughout and rear two keyframes. Therefore, for a video image sequence containing frequent motion, the number of key frames will have a phenomenon of image instability. Chapter 5 Multimedia Development Environment and Tools
Several concepts related to multimedia creative tools:
(1) Creative environment: The complete set of hardware used for creation, curing software (permanently built in hardware software) and software.
(2) Creative system: All software programs dedicated to creation in the environment.
(3) Creative Tools: A software program dedicated to creation in the environment, which can complete one or more creation tasks.
(4) Integration Tool: Used to arrange multimedia objects, handle its space-time relationship to become a tool for application software.
Chapter 6 Multimedia Application Development
Multimedia application system:
Multimedia application systems are ultimate products made by experts or developers using computer language or multimedia creative tools. At present, the application sector involved in multimedia applications mainly has cultural education (teaching software), electronic publishing, audio-visual production, film and television production, film and television stunts, development systems, communications and information consulting services.
(1) Development System: It is a tool-based or support software system used to develop applications, such as creative tools, database systems, book languages, multimedia editing, etc.
(2) Title is a class of multimedia applications, mainly to refer to applications with a certain topic, such as the capital, dictionary, textbook, a special introduction (such as scenery, monuments, stamps), etc .;
(3) Demonstration System: Specially designed specifically for a certain unit or a demonstration system, more emphasis on the idea or application requirements. For example, the introduction of the unit, the demonstration of the product, a scientific research project performance, etc.
(4) Education and training: Complex information organization format and interaction is characterized by this type of system. Because in the teaching process, it is not only the performance information, but also constantly intersecting the test, answers, exercises, etc.
(5) Entertainment: Multimedia games, film and television programs, etc., which are more emphasizes interactivity and real-time, and does not necessarily require large amount of information and accuracy;
(6) Special application system: Such systems are designed for specific purposes, such as multimedia conferencing systems, medical diagnostic systems, etc., itself has distinct professional characteristics.
The above is a variety of major multimedia applications. In these applications, some need to develop in a suitable language, emphasize strong programming capabilities, such as subsection (1); if some requires the use of suitable creation tools to be used, emphasizing multimedia Information organization and creativity, such as subsection (2), (3), (4); some require more complex system structure design or technological design, such as the last two categories. This is the respective characteristics of different multimedia applications.
Chapter 7 Multimedia Card
1. Basic technical indicators of audio card
(1) Sampling frequency: The number of sampling in unit time is 11.025 kHz, 22.05kHz and 44.1 kHz.
(2) Quantization bit of the sampling value: 8 bits, 16 and 32, which are mainly used in 16 bits.
(3) Number of channels: The audio card supports mono and double channels.
(4) Synthesizer: Commonly used methods have wave tables inquiry and frequency modulation (FM), the former has a good effect, but the latter is widely used in low prices. (5) MIDI interface: The audio card should support the MIDI standard.
(6) I / O device support: including a CD-ROM interface (SCSI interface, AT-bus interface), microphone input interface, speaker output interface, MIDI interface, line input interface, etc.
(7) Plug and play.
(8) Compatibility, etc.
2, wave form
The wave form synthesizer is one of the sound signal synthesizer. It is to digitize the natural sound, and store the recorded digitized sound signal in a table (ROM), and then call out the sound from it. Method of playback. The wave form synthesizer is played by the reproduction of natural sound, more natural, realistic, so modern excellent sound cards use wavefringing synthesizers.
3, DMA channel number, IRQ number and I / O port number
Installation with the PNP sound card is often related to the settings of the DMA channel number, IRQ number, and I / O port numbers. In fact, the above three parameters are not alone, and the general hardware card basically has three parameters. . At the same time, the same DMA channel number, IRQ number and I / O port number can only be assigned to a device, which is the principle of allocation of IRQ, DMA, I / O port address, violating it, conflicts The consequences may be very serious: IRQ conflicts may often cause system crash; DMA conflicts will cause conflict parties to work properly; I / O port conflict is also true.
In order to solve the conflict between the DMA channel number, IRQ number, and I / O port number, Microsoft and Intel have formulated the Plug and Play standard (PNP, PLUGANDPLAY) of the ISA bus. Peripherals that meet plug and play standards will no longer need to set IRQs, DMA, I / O port addresses themselves, and the system will automatically assign them from available system resources.
Chapter 8 CD and CDL
1, general characteristics of the CD-ROM drive
(1) Capacity: up to 680M bytes, can put China Encyclopedia (about 125.68 million words, total 74 volumes, Figure 49765).
(2) Built-in and external: The CD-ROM drive has built-in, external and portable depending on the position and form placed. The built-in drive application is the most widely used.
(3) Interface: Common CD-ROM Drive Interface Standard has SCSI interface, dedicated interface, IDE interface, etc.
(4) Speed: The access / seek time and the average data transfer rate (Kb / s) are measured.
(5) Buffer: Most drivers with buffers to improve read and write performance, typical buffer size is 64KB, 128KB, 256KB.
(6) Compatibility: Supports Photo CD and CD-ROM XA.
(7) Applying mechanism: At present, the tray-type disc mechanism is currently.
2, the characteristics of the CD series
(1) CD-DA: It is a specifications set for laser digital audio records. It is the first text of the CD standard belongs to the Red Book Standard.
(2) CD-ROM: The logical format formatted on the basis of CD-DA successfully, in 1988, became an international standard ISO 9660, called a shaft.
(3) CD-I: belongs to the green paper standard. It supplements the provisions of audio, video, and computer programs on the basis of CD-ROM standards. (4) CDROM XA: is a CDROM extension structure developed by Philips, Sony, and Microsoft. It expands the encoding of the digital audio signal to compensate for the problems brought by the CDI standard. It is the "bridge" product between CD-ROM and CD-I, realizes the same rail of the disc, video, and text simultaneously on the same rail, which is called the scales of the yellow book.
3, Photo CD: It is a film disc that allows multiple sections to record into the white paper standard.
4, DVD-ROM and CD-ROM
DVD Chinese translated into a "digital video disk", which uses MPEG2 compression criteria, using two-sided processes in DVD discs, 7 ~ 10GB digital information on the 12CM CD, can store the playback time of 270 ~ 284 minutes with higher quality film and television program . Become a next-generation product instead of VCD.
The DVD-ROM uses a CD-ROM of DVD discs, which can be compatible with various discs such as CD, CD-ROM, VCD, DVD.
The DVD and VCD have the following differences. The DVD uses MPEG2 encoding, video up to about 1000 lines of image resolution; and ordinary VCD uses MPEG1 encoding, only less than 400 lines; DVD uses Dolby AC3 surrounded, and VCD uses ordinary two-channel stereo Output. The DVD single-layer single-sided data capacity is 4.7GB, while the VCD is only 650MB, and the DVD can be made as double-sided double layer, with a total capacity of 17GB. The VCD standard is only single-sided single layer. For the need for protecting intellectual property rights, DVD has anti-copy location coding protection, while VCD is not.
Chapter 9 Common Multimedia Equipment
1, the structure of the scanner
The scanner consists of a charge coupled device (CCD) array, the light source, and the focus lens. CCD is arranged in a row or an array, and each device in the array can turn the optical signal into an electrical signal. The amount of electricity generated by the photosensitive device is proportional to the received light amount.
2, technical indicators for scanners
(1) Scanning resolution: The unit of pixel can be distinguished in units of DPI. The high and low of the input resolution directly determines the scanning precision, the higher the resolution, the higher the clarity of the sampling image.
(2) Grayscale: It is a major technical indicator of the scanner, also known as photoelectric conversion accuracy, refers to the ability to identify and reflect the degree of imagination. If each image is used to use 8-bit encoding, 256 grayscale levels can be reflected. Although the distraction of the human eye to the luminous body is higher than the 256-level brightness, the 256-level brightness has basically felt that there is no difference.
(3) Color accuracy: The color scanner is chromatic in pixels, and disbands a pixel point into a combination of red (R), green (G), blue (B). The degree of shades of each base color also uses a grayscale class, called color accuracy. Usually, 8 digits are taken when processing, ensuring 16.7m color reproduction, called true color.
(4) Scanning speed: refers to the scan time at the specified resolution and image size. This is an index that cannot be ignored. If the scanning speed is too slow, other supporting devices will be idle.
(5) Scanning the web: It indicates the maximum size of the original, commonly used for A4, A3 format.
Chapter 10 Multimedia Application
1. Problems should be paid attention to in multimedia creation
The common features and basic elements of multimedia creation are: vivid and realistic sound effects, high-definition dynamic video, flexible and convenient interaction, harmonious unified friendly interface.
Multimedia creation, in addition to selecting the right multimedia creative tool, you have to build a multimedia creative toolbox (including material collection tools, editing tools) and common material libraries (such as background library, buttons, audio and photo library, etc.). In addition, you should also pay attention to the following points in creation: (1) The screen design should be equalized, concise, and consistency.
(2) Pay attention to the sound than the effect of the image and text, the dynamic element (video, music, sound) can cause more attention.
(3) Always use a transition of one or similar effects.
(4) It is necessary to advocate the design, integrating science and art of humanity. To construct a good menu tree, optimize user visual. Rationalize the display of the screen to ensure that the appropriate display rate and response time, and easy to learn, prompt information, the help information is clear, and the characters are easy to understand.
