Digital Video, its main features
Until recently, few people could have imagined that with an ordinary home computer it would be possible not only to watch your favorite movies, but also to create your own video library, digitize the content of old videotapes, edit family videos, and even create your own. movie masterpieces.
It all started in 1992, when IBM and Intel developed the Indeo software technology (short for Intel Video). With its help, users have the opportunity to digitize video and create video files on a PC, with subsequent playback on the monitor screen.
Initially, digital video was an analog signal converted to digital format. Furthermore, the conversion procedure itself inevitably led to a certain loss of quality. Today, VCRs and old VHS cameras are a thing of the past, and modern digital video cameras, DVD and Blu-Ray players, which allow you to receive a signal immediately in digital form, rule the ball. And analog television is gradually giving way to more progressive digital.
Key features of digital video
Digital video has five main characteristics: screen resolution, frame rate, color depth, bit rate (video transmission width), and image quality.
Screen resolution (resolution): indicates the number of dots (pixels) horizontally and vertically that make up the image (video frame) on the screen. When recording resolution, the value of the number of dots per line (horizontal resolution) is indicated first and then the number of lines involved in the image (vertical resolution). For example, for the European PAL video standard, the frame size is 720×576 pixels, for the North American NTSC standard – 720×480, for high definition video (HD 720p) – 1280×720, and for the new HDTV standard (Full HD) – 1920×1080 pixels. As you probably understand, the higher the screen resolution, the better the video quality.
The frame rate is a value that indicates how many frames are changed per second. The standard video playback speed is considered a value equal to 30 frames / s. For cinema, this figure is slightly lower and amounts to 24 frames / s.
Color depth (color resolution) is a characteristic that indicates the number of colors that can participate in the formation of a video image. The number of colors in digital video is measured in bits. So 1 bit can take two different values (0 or 1) and it only allows encoding two colors (usually black and white), respectively. With two bits, you can encode 4 colors (2 2 = 4), with three bits – 8 colors (2 3), four – 16 (2 4) and so on.
Typically, color resolution is described by special color models. In computer technology, the RGB (red-green-blue) model is used, which can be represented by the following most common color depth modes: 8-bit (256 colors), 16-bit (65,536 colors), and 24-bit (16,777 .216 colors). By the way, the human eye, according to various opinions, can perceive 5-10 million shades of color.
Bit rate (video stream width): Shows the number of video bits processed per second of time. In other words, this is the video transmission speed, which is measured in megabits per second (Mbps). The higher it is, the better the quality. For example, for the DVD video standard, the bit rate is about 5 Mbps and for the HDTV format, it is already 10 Mbps. By the way, most of the time the bit rate value is used to evaluate the quality of the video transmitted over the Internet.
Image quality is a characteristic designed to evaluate the quality of processed video compared to the original and is determined by a set of values for resolution, color depth, and video transmission speed.
Compression standards
One minute of pure, uncompressed and digitized sound takes up about 10MB on a computer’s hard drive, as a result of which, for the vast majority, music files are stored in a compressed form to save space. How long does a minute of uncompressed video take? For example, to place a 60-second video with a rate of 30 frames per second, a resolution of 720×576 pixels, and a color depth of 16-bit, you will need approximately one and a half gigabytes of free disk space. And this without taking into account the audio track. After these numbers, it is probably not necessary to explain why digital video is stored on our computers exclusively in compressed form.
There are several dozen popular compression formats that use different compression algorithms.
