What is digital video?
Digital video is a set of technologies for recording, processing, transmitting and storing images and sound from digital television. The main difference from analog video is that the video signal and sound are encoded and transmitted not in their original form, but after analog-digital conversion into video and sound data streams. In most cases, digital video is compressed to reduce the amount of data that is transmitted and stored. Digital video can be delivered to various video media through digital interfaces in the form of streams or files.
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 the 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.
Frame rate, frame rate (frames per second (FPS), frame rate, frame rate): the number of frames per unit of time in television and cinema. The concept was first used by photographer Edward Muybridge, who carried out chronophotography experiments of moving objects with multiple cameras in a row. The generally accepted unit of measurement is frames per second.
– 24 – the world standard for the frequency of filming and projection;
– 25 – the filming frequency used in the production of films and television reports for their translation to the European decomposition standard 625/50;
– 30 – Standard video playback speed.
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 (22 = 4), with three bits – 8 colors (23), four – 16 (24) 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 bits (256 colors), 16 bits (65,536 colors) and 24 bits (16,777. 216 colors). By the way, the human eye, according to various opinions, can perceive 5-10 million shades of color.
A pixel is the smallest element in a digital image in bitmap graphics. It is square in shape. “Pixel” is a word made up of the words “image” and “element”. The physical size of a pixel is not set by the user, but is determined by the characteristics of the display device. The more pixels a display device has, the finer details in the image can be displayed.
Video bit rate is the amount of information transmitted per second. From this it follows that the higher the video bit rate, the better it is, the clearer the image, the less artifacts, etc. And it takes more hard drive space to store this video and consequently more time to transfer it over the network.
Image quality is a characteristic designed to evaluate the quality of the processed video compared to the original and is determined by a set of values for resolution, color depth, and video transmission speed.
HD. High definition video. Most of the HD formats in use provide a resolution of 1920 x 1080 or 1280 x 720. There is a significant difference between the 1080 and 720 standards: the former uses 2.25 more pixels per frame.
This difference significantly increases the demands of 1080 data processing in terms of compression time, decompression speed, and size of the storage area. All 720 formats are progressive. The 1080 format is a combination of progressive and interlaced frame types. Computers and their monitors are inherently progressive, whereas television broadcasts
