Video
The video technology (lat. video = I see, from videre to see ) covers the electronic method for recording, transmission, processing and reproduction of moving images and also any accompanying sound (see audio). These also include the equipment used, such as video camera, video recorder and monitor. But even the purely digital processing of optical signals is counted for video technology.
Development
Analog video signals are known since the thirties of the 20th century. At this time, the technology, which led to the development of television later developed. Typical of analog video signals, the line scanning ( scan) an image in the interlace method. At the end of each scanned line is a jump back to the beginning of the next line at the end of the whole (half) image of the jump to the beginning of the scan. This is called the interlaced method. Until the eighties, the scan of an image for video purposes has typically been through the line at a deflection of an electron beam on a photosensitive layer.
The storage medium of image and sound data first served the magnetic tape, usually in a video cassette, in analog form, as in the Video Home System (VHS). Since 1996, digital recording is increasingly being used as the Digital Video (DV ) system for camcorders.
Recently, magneto- optical techniques are increasingly being used along with digital compression, so in DVD camcorders. Since the late 1990s in leveraging the digital MPEG technology standards. On it, among other things based video CD, DVD and Digital Video Broadcasting (DVB). It is distinguished from DV through further improved image quality, greater compatibility in the PC sector, as well as lighter and more extensive editing options. The MPEG -4 format offers over MPEG -2, in turn, a stronger compression but requires higher processor performance recording and playback. Also, it may come rather to loss of quality due to compression artifacts in MPEG-4.
PAL video
The Phase Alternating Line system ( PAL system ) is the TV standard used in the German language area. PAL was developed in 1963 by Telefunken. It contains 625 raster lines (scan lines) per image (frame), 25 frames per second, corresponding to a duration of 40 ms / frame. The screen aspect ratio is 4:3, so the pixels are not square to oppose the resolution of 720x576 pixels ( 5:4 ). PAL uses the YUV color model. The representation is in interlace mode, each image is thus divided into two fields, one with the even and odd one with the grid lines. Because of the picture change gap only 576 lines are visible. PAL is used as in Brazil, China, Germany, Austria, Switzerland and India.
NTSC video
NTSC is the 1953 by the NTSC (National Television Systems Committee ) established U.S. television standard. NTSC has 525 scan lines per image, play with exactly 29.97 frames per second, corresponding to 33.37 ms per image. From time to time one reads 30 frames per second, but this is incorrect. The aspect ratio is 4:3, the pixels are square. The representation is in interlace mode, each picture is divided into two fields (Fields ), one with the straight and one with the odd scan lines. At the beginning of each field 20 raster lines are reserved, therefore, remain a maximum of 485 raster lines for image information. Of these, however, are in turn only 480 visible. Therefore, NTSC has a resolution of 640 x 480 pixels. NTSC uses the YIQ color model, and is used among other things in Japan, USA, Canada and Korea.
Analog recording formats
VHS - Video Home System - was developed in the late seventies by JVC. Thanks to a clever marketing strategy, sat down with technically intelligent solutions such as video world by 2000. The magnetic tapes of VHS tapes are sensitive to noise. They are 1.27 inches wide. Video tape recording systems exist in many versions with different signal processing and various mechanical and [ sic] tracking parameters. The special feature of the video area is the one in the high upper limit frequency, which is about 250 times higher with about 5 MHz and the audio signal, and on the other hand, in the very low lower cut-off frequency close to 0 Hz, a high signal frequency can only be achieved at a high relative velocity. Therefore, VCR work with rotating heads.
Digital video technology
The replacement of analog video technology towards digital process was driven mainly by the graphical data processing. Graphics cards of PCs are powerful and nowadays the average user can also render his own little movies. Therefore, offer digital storage systems, such as external hard drive, on top of that have the advantage to be played on again. Digital signals are derived from analog signals by these periodically samples (samples) taken and are assigned from a finite speed range the values of the numbers of samples.
Format development
The recording technique and thus the two formats have roughly developed in the following steps:
- Analog recording on magnetic tape, analog processing: VHS, Video -8; Video 2000
- Digital recording on magnetic tape, digital processing: ( mini ) DV and digital video editing;
- Digital recording to DVD or hard drive with compression, usually MPEG -2;
- Digital recording on a memory card, usually stronger compression, such as with MPEG-4.