HOMEVIDEO

Video (from Lat. Video - look, see) - a term understood that a wide range of recording technology, processing, transmission, storage and playback of visual and audio-visual material on the monitors. When at home say «video» - they usually have in mind the video, TV or movie recorded on a physical medium (tape, DVD, etc.). The number of frames per second 

Number (frequency) frames per second - this is the number of still images that are to succeed each other when the 1 second video and that creates the effect of the motion of objects on the screen. The greater the number of frames per second, the more smooth and natural movement will appear. The minimum rate at which the motion will be perceived homogeneous - about 10 frames per second (this value individually for each person). In traditional film cinematography uses the frequency of 24 frames per second. TV system PAL SÉCAM and use 25 frames per second (eng. 25 fps or 25 Hz) and NTSC system uses 29.97 frames per second. Computer digital video quality, as a rule, the frequency of use 30 frames per second. The upper cut-off frequency twinkle, moving the human brain, an average of 39-42 Hertz and individually for each person. Some modern professional cameras can shoot at a frequency of up to 120 frames per second. A special camera for ultra-fast shooting filmed at a frequency of up to 1000 frames per second and above that required, for example, for a detailed study of the flight path of a bullet or structure vzryva.Cheresstrochnaya sweep 

Progressive video can be progressive (progressive) or interlaced. With progressive scan all the horizontal lines (rows) images are displayed alternately, one after another. But when interlace alternately showing all even, all odd-numbered lines (also called fields, frame). Interlace is often called in English manners interleys (eng. interlace) or interleysing. Interlace was invented to show the image on the tube and is used now to transfer the video to «narrow» channels, does not accept an image of the entire capacity. System PAL, SÉCAM and NTSC - it's a system with interlaced. New digital television standards, for example, HDTV provides a progressive scan. While the technology appeared to mimic the progressive-scan when the material interleysom. Interlace is usually indicated by «i» after the vertical resolution, eg 720 × 576i × 50. 

In order to suppress the unpleasant effects that arise when watching interlaced video on progressive screen, special mathematical techniques, called deinterleysingom.Razreshenie 

By analogy with the resolution of computer monitors, a video also has a resolution (eng. resolution), the horizontal and vertical, measured in pixels. Conventional analog TV resolution of 720 × 576 pixels for both PAL and SÉCAM, at a frequency of 50 hertz frame (one field, 2 × 25) and 720 × 480 pixels for NTSC, at a frequency of 60 hertz (one field, 2 × 29,97 ). In the expression 720 * 480 the first number indicates the number of dots in a horizontal line (horizontal resolution) and the second number the number of lines (vertical resolution). The new standard vysokootchetlivogo (English high-definition) digital television HDTV requires permission to 1920 × 1080 at a glimpse 60 Hz progressive scan. That is 1920 pixels per line, 1080 lines. 

Resolution in the case of three-dimensional video is measured in vokselyah - features images of points (cubes) in the three-dimensional space. For example, a simple three-dimensional video is now used mainly authorization 512 × 512 × 512, examples of such a demonstration video available today, even at PDA.Sootnoshenie side 

The ratio of width and height of the frame (eng. aspect ratio) - a critical parameter in any videos. Even with the 1910 film had a screen aspect ratio 4:3 (4 units wide by 3 units high, sometimes even written as 1,33:1 or 1.33). It was felt that, given the existence of two human eyes, the viewer is more convenient to watch a movie on the screen of this form. When television appeared, they took over this ratio, and almost all of the analog TeleSystems (and, hence, televisions) have 4:3 aspect ratio screen. Computer monitors also inherited the broadcast standard sides. While still in the 1950's, it is about 4:3 has changed. The point is that the field of view of rights is by no means the ratio of 4:3. Because the human eye 2, located on a horizontal line - hence, the field of view of people close to the ratio of 2:1. To bring the frame to form the natural human field of view (and, therefore, enhance the perception of the film), was introduced the standard 16:9 (1,78), almost the so-called «golden section». Digital TV is also largely focused on the ratio of 16:9. By the end of XX century, after some additional research in this area, began to appear even more radical frame ratio: 1,85, 2,20 and up to 2.35 (about 21:9). All this, according to the creators, is designed to immerse the viewer deeper into the atmosphere viewed the video. There are alternative explanations of the transition to wide format: the opportunity to hire in the rooms, did not adapt to film, the desire for lower quality pirated videokopy and television kopiy.Kolichestvo colors and color resolution 

Number of colors and color resolution of the video describes the color models. For PAL standard color model used YUV, for SÉCAM model YDbDr, for NTSC model YIQ, in computer technology is applied in RGB (and αRGB), fewer HSV, and in print technology CMYK. The number of colors that can display a monitor or projector depends on the quality of your monitor or projector. The human eye can perceive, according to various estimates, from 5 to 10 million shades of colors. Number of colors in the video is determined by the number of bits allocated to encode the color of each pixel (English bits per pixel, bpp). 1 allows to encode 2 bits of color (usually black and white), 2 bits - 4 colors 3 bits - 8 colors, ..., 8-bit - 256 colors (28 = 256), 16-bit - 65 of 536 colors (216), 24 bits - 16 777 216 colors (224). In computer science there is a standard and 32 bits per pixel (αRGB), but the additional α-byte (8 bits) is used to encode the coefficient of transparency of pixel (α), and not to transfer the color (RGB). When a pixel display adapter, RGB-value will change depending on the value of α-byte and the pixel color to be (which will be «seen» through «transparent» pixel), then α-byte will be discarded, and the monitor will only color signal RGB . Bitrate or the width of the video (digital video) 

The width (or velocity) or the video bitrate (eng. bit rate) - this is the number of bits per second of video time (indicated by «bps» - bits per second, or more often «Mbps» - megabits per second, in English marking «bit / s» and «Mbit / s» accordingly). The higher the width of the video, so in general a better quality video. For example, the width of VideoCD format for video is only about 1 Mbit / s and for DVD is about 5 Mbps. Of course, the subjective difference in quality can not be estimated as five times, but this is objectively true. A format of digital TV HDTV video using the width of about 10 Mbps. With the speed of the video is also very convenient to evaluate the quality of the video when it is transmitted over the Internet. 

There are two types of control flow in the width of video - a constant bitrate (eng. constant bit rate, CBR) and variable bitrate (eng. variable bit rate, VBR). The concept of VBR, now very popular, is designed to preserve maximum video quality, while reducing the total amount of transmitted video. In this fast-motion scenes, the width of the video is increasing, while the slow scenes where the picture is changing slowly, the width of the flow drops. It is very convenient for the buffered video and stored video transmission over computer networks. But for bezbufernyh real-time systems and direct broadcast (for example, teleconferencing) are not appropriate - in these cases it is necessary to use a constant speed videopotoka.Kachestvo video 

Video quality is measured by means of formal metrics like PSNR or SSIM, or using subektivnogo comparison with experts. 

Subektivnoe video quality is measured by the following methods: 
Sequences were selected for use in testing 
Selected measurement system 
Selects the method of displaying video and counting the results of measurements 
Are invited to attend the required number of experts (usually not less than 15) 
A test is 
Calculated the average score on the basis of expert evaluations. 

Several methods subektivnoy assessment described in the recommendations ITU-T BT.500. One of the commonly used methods of evaluation - it DSIS (eng. Double Stimulus Impairment Scale), in which experts, first show the original video, and then processed. Then the experts evaluate the quality of treatment, varying assessments of the «invisible Processing» and «Processing improves video» to «treated seriously annoying video». Stereoscopic Video 

Stereoscopic video or just stereovideo (eng. stereoscopic video and 3D video) was very popular in the late XX century, and now regularly encountered a wave of interest in it. Throughout the world there is a cinema, which with the help of a technology play stereoscopic video. For stereovideo need two video, called layers: one for the left eye, the other for the right. Thus the audience a sense of volume, three-dimensional video, enhanced sense of realism view. At about the same quality, but weaker effect allows viewing of video in plastic glasses with one red lens and one blue or green. New technologies, presented in 2006, in particular, HD DVD discs and Blu-Ray, permit to carry more stereovideomateriala and to do homework and stereoscopic video more accessible.

HOMEVIDEO