Representation of digital media in computers

In computers, information is encoded in patterns of 0s and 1s. These numbers are called bits (which means binary digits). Although you might be tempted to associate them with the numbers 0 and 1, they’re just symbols whose meaning depends on the application your computer is working with: sometimes they represent numbers, sometimes sounds, and sometimes images.

Digital audio

Digital audio is a technology that records, stores, encodes, compresses and transmits sound by digital means. The data in the computer are stored in binary form. Audio digitization is to convert the analog sound signal in the form of sine wave into a binary digital signal. Playback converts a digital signal to an analog level signal.

The conversion of analog signals to digital signals usually requires a series of processes such as sampling, quantization and coding. We will focus on pulse coded modulation, which is the most common and simplest form of waveform encoding.

Sampling

Digital-to-analog conversion is a process that takes an amplitude value on the analog sound waveform at every time interval, and changes the continuous waveform in time domain into a finite number of discrete values.

Quantization

The process of changing an infinite number of continuous samples in the sampled amplitude into a finite number of discrete values. Firstly, the whole amplitude is divided into a set of finite amplitude (quantization step), and the samples falling into a certain step are grouped into the same class and assigned the same quantization value.

Coding

The quantized signal is not yet a digital signal, and it needs to be converted into a digitally coded pulse, a process called encoding. Common forms of encoding are binary encoding. Specifically, n bits binary codes are used to represent the quantized sample values, each binary number corresponds to a quantized value, and then they are arranged to obtain a digital information flow composed of binary pulses. At the receiving end, the encoding process can reconstruct the original sample value according to the received information, and then recover the original signal through a low-pass filter. The frequency of the pulse train formed in this way is equal to the product of the sampling frequency and the number of quantization bits, which is called the bit rate of the transmitted digital signal. Obviously, the higher the sampling frequency, the larger the number of quantization bits, the higher the bit rate, and the wider the required transmission bandwidth.

Digital image

One way to represent an image is to think of an image as a set of points, and each point is called a pixel. Each pixel of the display is then encoded, and the entire image is represented as a collection of these encoded pixels, which is called a bitmap. This approach is very common.Printers and monitors operate based on the concept of pixels.

The way the pixels in the bitmap are encoded varies from application to application. For simple black and white images (also known as grayscale images), each pixel is represented by one bit, usually 0 for black and 1 for white. A simple black and white image is actually a matrix of 0s and 1s in a computer. For more elaborate black and white images, each pixel is represented by a set of bits (usually eight), and eight bits can be represented by three binary numbers, that is, three binary numbers representing eight middle shades of black to white, allowing many shades of gray to be represented as well.

Color image is based on this is composed of many colors, according to the optical three primary color theory, optical three colors (red, green and blue) mixed, can form any display screen color. Thus, each color image is composed of three channels of these three colors (red, green, and blue). This means that in a color image, the number of matrices or the number of channels will be more. These pixels also have values from 0 to 255, but instead of the intensity of the black and white shadow, each number represents the intensity of the red, green, and blue shadow. Finally, all these channels or all these matrices will be superimposed so that when the shape of the image is loaded into the computer, it will be. Where X is the number of pixels in the whole height, Y is the number of pixels in the whole width, and 3 represents the number of channels. As shown in Figure 8-4, a color image is composed of three channels, namely R, G and B.

Digital video

Video is the expression form of a series of motion related still images. When it is played continuously, the human eye can see the continuous dynamic images. It also refers to a series of technologies that capture, record, process, store, transmit and reproduce the motion related still images in the form of electrical signals. When the continuous image changes more than 24 frames per second, the human eye cannot distinguish a single static image according to the principle of persistence of vision. It looks like a smooth continuous visual effect, and such a continuous picture is called a video.

Video technology was originally developed for television systems, but has now evolved into a variety of different formats for consumers to record video. With the development of network technology, video clips exist in the form of streaming media on the Internet and can be received and played by computers.

Your task

What is the digitization of sound signals?

*Share your thoughts and ideas in the comments below.