ICT
Created by
Krugova and Semenyuk
All known formats for representing images (both motionless and moving) can be divided into raster and vector. In vector format, the image is divided into primitives - straight lines, polygons, circles and segments of circles, parametric curves filled with a certain color or pattern, connected areas, typed text fragments, etc. Examples of two-dimensional vector formats - PostScript, PDF (Portable) Document Format, a specialized subset of PostScript), WMF (Windows MetaFile). In raster format, the image is divided into a rectangular matrix of elements called pixels (slightly distorted PICture ELement - picture element). The matrix is called raster. For each pixel, its brightness is determined and, if the image is color, the color. If, as is often the case when digitizing real scenes or converting to raster format (rasterization) of vector images, several elements have got into one pixel, their brightness and color are averaged taking into account the occupied area. When digitizing, averaging is performed by the analog circuits of the analog-to-digital converter, when rasterized - by anti-aliasing algorithms.
Image
Two-dimensional vector image
Three-dimensional vector image
The methods and methods of working with audio information came to computer technology the latest. In addition, unlike numerical, text and graphic data, sound recordings did not have an equally long and proven history of coding. As a result, methods of encoding audio information with binary code are far from standardization. Many individual companies have developed their own corporate standards, but there are two main areas among them.
Audio
The FM (Frequency Modulation) method is based on the fact that theoretically any complex sound can be decomposed into a sequence of simple harmonic signals of different frequencies, each of which is a correct sinusoid, and, consequently, can be described by numerical parameters, i.e. code. In nature, sound signals have a continuous spectrum, i. E. are analog. Their decomposition into harmonic series and representation in the form of discrete digital signals is performed by a special device - analog-digital converters (ADCs). The reverse conversion is performed by digital-to-analog converters (DACs) to reproduce sound encoded with a numeric code. With such transformations, loss of information associated with the coding method is inevitable, therefore the quality of sound recording is usually not quite satisfactory and corresponds to the quality of the sound of the simplest electric musical instruments with the color characteristic for electronic music. At the same time, this method of copying provides a very compact code, so it found application even in those years when the resources of computer facilities were clearly insufficient.
The method of table Wave (Wave-Table) synthesis better corresponds to the current level of technology development. Pre-prepared tables contain samples of sounds for a variety of different musical instruments. In the technique such samples are called samples. Numeric codes express the instrument type, model number, pitch, duration and intensity of the sound, the dynamics of its change, some parameters of the environment in which the sound occurs, and other parameters that characterize the features of the sound. Since real sounds are performed as samples, its quality is very high and approaches the quality of sound of real musical instruments.
Recently, the computer is increasingly used to work with video information. There are many different formats for presenting video data. In the Windows environment, for example, for more than 10 years (starting with version 3.1), the Video for Windows format is being used, based on universal files with the AVI extension (Audio Video Interleave - alternating audio and video). The essence of AVI files is the storage of structures of arbitrary multimedia data, each of which has a simple form. The file as such is a single unit, and new blocks can be embedded into it, just like in any other block. Note that the block identifier determines the type of information that is stored in the block. Absolutely arbitrary data can be stored inside the original information container (block) described above, including, for example, blocks compressed by different methods. Thus, all AVI-files only look the same in appearance, but inside they can differ very much.
Video
More universal is the multimedia format Quick Time, originally originated on Apple computers. Compared to the above, it allows you to store independent pieces of data, even without the common time synchronization, as required by AVI. As a result, in one file, for example, a song can be stored, text with its words, a musical notation in MIDI format, capable of controlling the synthesizer, etc. A powerful feature of Quick Time is the ability to create an image on a new track by referencing frames that are available on other tracks. The track obtained in this way turns out to be incommensurably smaller than if the required frames were copied to it. Thanks to the described feature, a file of this type can easily contain not only a full high-quality version of the video, but also a special "simplified" copy for slow computers, as well as a commercial that is a "squeeze" from the full version. And all this without a special increase in volume compared to the full copy.
More and more popular in recent years are video compression systems, which allow some unobtrusive image distortions to increase the compression ratio. The most famous standard of this class is MPEG (Motion Picture Expert Group), which is developed and constantly developed by the Committee (Group of Experts) of the international organization ISO / IEC (International Standards Organization / International Electrotechnical Commission) established in 1988 for high-quality compression of moving images standards. The methods used in MPEG are not easy to understand and rely on fairly complex mathematics. We indicate only the most general methods, due to which compression is achieved. First of all, the processed signal from the RGB-representation with peer components is converted into brightness and two "coordinates" of chroma. As experiments show, color components are less important for perception and they can be halved. In addition, special mathematical transformations (DCT - discrete-cosine transform) are made, somewhat obscuring the image in small details. Again, it follows from experiments that on the subjective perception of an image this practically does not affect. Finally, by special methods, a strong redundancy of information is eliminated, due to weak differences between neighboring frames. The data obtained as a result of all the described procedures is further compressed by common methods, similar to how it is done when archiving files.
Recently, the technology called DivX (derived from the abbreviation of the words Digital Video Express, denoting the name of the video system, which "became famous" for an unsuccessful attempt to charge a small fee for each video disc viewing, is becoming increasingly popular. Thanks to DivX, it was possible to achieve a compression ratio that allowed to mix a quality recording of a full-length movie onto one CD-ROM - compress a 4.7 GB DVD movie to 650 MB. And although this achievement, unfortunately, is most often used for pirated copying, this in itself does not detract from the merits of the new technology. As well as the fact that the very first version of DivX compression was worked by French hackers from MPEG-4 - modern versions of DivX no longer have anything to do with this event.
The most popular video playback programs allow using replaceable subsystems for compressing and restoring video data - codecs (from English compression / decompression - codec, compare with the formation of the term "modem").
This approach makes it easy to adapt new technologies as soon as they become available. Replacement codecs are good for both users and software developers. Nevertheless, a great variety of codecs creates certain difficulties for producers of video products. Often, as an exit from the situation, the necessary codecs are placed on a movie CD or even deliver video materials in several variants, thus providing an opportunity to choose the right one. Increasingly, automation of recognition is spreading when the player finds information about the missing codec, loads it from the Internet.
Any text consists of a sequence of characters. Characters can be letters, numbers, punctuation marks, mathematical action signs, round and square brackets, etc. Text information, like any other, is stored in the computer's memory in binary form. For this, each symbol is associated with a certain non-negative number, called the symbol code, and this number is written into the computer's memory in binary form. The specific correspondence between the symbols and their codes is called the coding system. In modern computers, depending on the type of operating system and specific application programs, 8-bit and 16-bit (Windows 95, 98, NT) character codes are used.
Text
In personal computers, the ASCII (American Standard Code for Information Interchange) system is commonly used. It was introduced in 1963 and assigns to each symbol a seven-bit binary code. It is easy to determine that 128 characters can be represented in the ASCII code. Two basic and extended coding tables are assigned to the ASCII system. The base table fixes the code values from 0 to 127, and the extended one refers to the symbols with numbers from 128 to 255. The international standard, in which the character encoding of the Russian language is provided, is called ISO (International Standard Organization). In practice, this encoding is rarely used. UNICODE - character encoding not by eight-bit binary numbers, but by numbers with a large bit, a system based on 16-bit character encoding
A computer is an electronic machine that works with signals. The computer can only work with such information, which can be turned into signals. If people could convert signals into taste or smell, then the computer could work with such information. The computer is very good at working with numbers. He can do anything with them. All the numbers in the computer are encoded with a "binary code," that is, they are represented by just two characters 1 and 0, which are easily represented by signals.
All information with which the computer works is encoded in numbers. Regardless of whether the graphic, text or audio information is so that it can be processed by the central processor, it must somehow be represented by numbers.