Text, Sound, Video and Images

Text

Text refers to the form of written language. From a literary point of view, it is usually a sentence or a combination of sentences with complete, systematic meaning (message). A text can be a sentence, a paragraph or a chapter.

In literary theory, a text is any object that can be "read", whether this object is a work of literature, a street sign, an arrangement of buildings on a city block, or clothing styles. It is a coherent set of signs that transmits some kind of informative message. This set of signs is considered in terms of the informative message's content, rather than in terms of its physical form or the medium in which it is represented.

Within the field of literary criticism, "text" also refers to the original information content of a particular piece of writing; that is, the "text" of a work is that primal symbolic arrangement of letters as originally composed, apart from later alterations, deterioration, commentary, translations, paratext, etc. 

Therefore, when literary criticism is concerned with the determination of a "text", it is concerned with the distinguishing of the original information content from whatever has been added to or subtracted from that content as it appears in a given textual document (that is, a physical representation of text).

Since the history of writing predates the concept of the "text", most texts were not written with this concept in mind. Most written works fall within a narrow range of the types described by text theory. The concept of "text" becomes relevant if and when a "coherent written message" is completed and needs to be referred to independently of the circumstances in which it was created.

Sound

A sound wave generated by the vibration of an object. It is a wave phenomenon that is transmitted through a medium (air or solid, liquid) and can be perceived by human or animal hearing organs. The object that originally vibrates is called the sound source. The sound propagates in the form of waves. Sound is the movement of sound waves through the propagation of any substance.

Decibel is a unit used to indicate the intensity of sound, which is recorded as dB.

Sound is a kind of fluctuation. When playing instrument, tapping a door or hitting a tabletop, the vibration of the sound will cause the medium-air molecules to have rhythmic vibrations, causing the surrounding air to change densely and form a dense and longitudinal longitudinal wave. This creates a sound wave that continues until the vibration disappears.

Sound can always be broken down into superposition's of sine waves of different intensities of different frequencies. This process of transformation (or decomposition) is called the Fourier transform.

Therefore, the general sound always contains a certain frequency range. The frequency of the sound is usually expressed in Hertz and is recorded as Hz, which refers to the number of periodic vibrations per second. As a wave, the sound with a frequency between 20 Hz and 20 kHz can be recognized by the human ear. Fluctuations above this range are called ultrasonic waves, and below this range are called infrasound waves.

Characteristics of sound

• Loudness: The subjectively perceived size of the sound (commonly known as the volume) is determined by the "amplitude" and the distance of the person from the sound source. The louder the amplitude, the greater the distance between the person and the sound source, and the louder the louder between the person and sound source. (Unit: decibel dB)

• Pitch: The level of the sound (treble, bass), determined by the "frequency", the higher the frequency, the higher the pitch (frequency unit Hz, human ear hearing range 20 ~ 20000Hz. 20Hz below is called infrasound, 20000Hz or more is called ultrasonic For example, the sound of the bass end or the higher sound, such as a stringed sound.The frequency is the number of sound waves passing through a given point per second. It is measured in Hertz and is named after Heinrich Rudolf Hertz. This person has set up a table to show how the frequency is related to the period per second.1 kHz or 1000 Hz means that there are 1000 cycles of sound waves passing through a given point per second, 1 MHz is 1,000,000 cycles per second, and so on.

• Tone: Also known as the sound, the waveform determines the sound of the sound. Sound has different characteristics due to the characteristics of different object materials. The sound itself is an abstract thing, but the waveform is an abstract and intuitive expression. The sound is different and the waveform is different. Typical tone waveforms include square waves, sawtooth waves, sine waves, pulse waves, and so on. Different sounds, through the waveform, are completely distinguishable.

• Music: There are regular, pleasant sounds. Noise: From a physics point of view, the sound produced by the sounding body as a random vibration; from the perspective of environmental protection, all the sounds that interfere with people's normal work, study and rest, and the sounds that people want to listen to interfere with sound.

Tone, loudness, and timbre are the three main characteristics of music. People use them to distinguish sounds.

When two objects collide and vibrate to produce sound, if the vibration frequency ratio is a non-reducible complexity ratio, such as: 201:388, then we will distinguish this sound as harsh, if, on the other hand, if the vibration frequency ratio is The simpler ratio that can be simplified, such as: 3:7, then we will feel very pleasant when we distinguish it. (Pythagoras found)

The transmission of sound requires matter. In physics, such matter is called a medium. This medium can be air, water, or solid. Of course, in a vacuum, sound cannot propagate. The speed at which sound travels in different media is also different. The speed of sound propagation is related to the counter-balancing force of the medium. 

When a certain molecule of a substance deviates from its equilibrium position, the surrounding molecules will squeeze it back to the equilibrium position, and the counter-strength force is greater. The faster the sound spreads. The resistance of water is greater than that of air, and the resistance of iron is greater than that of water.

The spread of sound is also related to temperature and resistance.

The sound will also be refracted by the blockage of external materials. For example, when people face the mountains and shout, they can hear their own echoes. Another example is refraction: the sound of the night spreads farther than the daytime, because during the daytime the sound is in the process of spreading, it encounters rising hot air, which refracts the sound quickly into the air; the cold air drops at night, the sound will follow The surface is slowly spreading, and it is not easy to refract.

3.Video

Video refers to various technologies that will capture, record, process, store, transmit and reproduce static images as electrical signals. When the continuous image changes more than 24 frames, according to the principle of visual persistence, the human eye cannot distinguish the static picture of a single frame; it seems to be a smooth continuous visual effect, so that the continuous picture is called video.

Video technology was originally developed for television systems, but has now evolved into a variety of formats for consumers to record video. The development of network technology can also be carried on the form of streaming media through the record segment of the video and received and played by the computer. Video and film are different technologies, and photography is used to capture dynamic images as a series of still photos.

Video usually refers to storage formats for various motion pictures, such as digital video formats, including DVD, QuickTime, and MPEG-4, and analog video tapes, including VHS and Betamax. 

Video can be recorded and transmitted over different physical media: electrical signals when the video is captured or transmitted by radio, and magnetic signals when recorded on the tape; the actual transfer and capture of the video quality and storage The way it changes.

Property introduction

Screen update rate:

Frame rate is the number of static pictures played per second by the video format. Typical picture update rates range from early 6 or 8 frames per second to 120 frames per second today. Movie film is shot at a slightly slower 24fps; this usually requires some complicated conversion process when the TV broadcasts the movie. Approximately 10fps is required to achieve the most basic visual persistence.

Resolution:

The screen size of various TV specification resolution comparison videos is called "resolution". Digital video is preset in scale units, while analog video is measured in number of horizontal scan lines.

The new HDTV resolution is 1920×1080p60, which means that there are 1920 values per horizontal scan line, and each screen has 1080 scan lines, which is played at a speed of 60 pictures per second.

Length to width the ratio:

The aspect ratio is used to describe the ratio of the video picture to the picture element. The traditional TV screen has an aspect ratio of 4:3.

HDTV has an aspect ratio of 16:9. The 35mm film negative has an aspect ratio of about 1.37:1.

4.Image

An image is a material representation of a person's perception of vision. Images can be acquired by optical devices such as cameras, mirrors, telescopes, and microscopes; they can also be created by hand, such as by hand painting. 

The image can be recorded and stored on a medium sensitive to optical signals such as paper media, film, and the like. With the development of digital acquisition technology and signal processing theory, more and more images are stored in digital form. Thus, in some cases the term "image" actually refers to a digital image.Images are divided into still images, such as pictures, photos, etc., and motion pictures, such as movies.

An image is a visual symbol. Through professionally designed images, you can develop a visual language for communication between adults and people. It can also be a historical material for understanding the culture and history of ethnic groups. A large number of plane paintings, three-dimensional sculptures and architectures in the history of world art can also be regarded as the image cultural assets of human beings developed from ancient and modern civilizations.

Digital image

A digital image is a representation of a two-dimensional image with a finite number of numerical pixels.

Digital image software

Geographic information system for digital image production

Typically, pixels are stored in a computer as raster images of a two-dimensional array of integers, which are often transmitted and stored in a compressed format.

Digital image type

The pixels of each image typically correspond to a particular 'position' in a two-dimensional space, and one or more sample values associated with that point constitute a value. According to the number and characteristics of these samples, different digital images can be divided into:

Binary image

The luminance value of each pixel in the image can only be taken from an image of 0 or 1, and is therefore also referred to as a 1-bit image.

Grayscale image: Also known as grayscale image: Each pixel in the image can be represented by a luminance value from 0 (black) to 255 (white). Between 0 and 255 represents a different gray level.

Digital images function

Used to represent data distributed over a three-dimensional space, such as images generated by a computed tomography device, in which case each data is referred to as a voxel.

Digital image display

Currently popular image formats include raster image formats BMP, GIF, JPEG, PNG, etc., as well as vector image formats WMF, SVG, and the like. Most browsers support direct display of GIF, JPG, and PNG images.

Color images

Color images are mainly divided into two types, RGB and CMYK. The color image of RGB is composed of three different color components, one is red, one is green, and the other is blue. The CMYK type image is composed of four-color components: C, M, Y, and K. CMYK type images are primarily used in the printing industry.

False color image

Stereoscopic image

 A stereoscopic image is a pair of images taken by different angles of an object. Normally, we can calculate the depth information of an image using a stereo image.

Three-dimensional image: A three-dimensional image is composed of a set of two-bit images of a stack. Each image represents a cross section of the object.