Video technology

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The video technology ( latin video , I see ', from videre , see'), short video called electronic process for including recording , transmission , processing and playback of moving images and possibly the accompanying sound (see audio ). This also includes the devices used, such as video cameras , video recorders and screens . The purely digital processing of optical signals is also counted as part of video technology.

development

Analog video signals have been known since the 1930s. It was at this time that the technologies emerged that would later lead to the development of television. Typical for analog video signals is the line-by-line scanning of an image in the interlaced process. At the end of each scanned line there is a jump back to the beginning of the next line, at the end of the entire (half) image there is a jump to the beginning of the scanning field. This is called the interlace procedure. Up until the 1980s, an image was typically scanned for video purposes by deflecting an electron beam line by line over a light-sensitive layer.

The magnetic tape , usually in a video cassette , in analog form, as in the Video Home System (VHS) , was initially used as the storage medium for the image and sound data . Digital recording has been increasingly used since 1996, for example in the digital video (DV) system in camcorders .

Recently, magneto-optical methods have been increasingly used together with digital compression , for example in DVD camcorders . Digital MPEG technology has been setting the standards since the late 1990s . Based on it include the CD video , the DVD and the Digital Video Broadcasting (DVB). Compared to DV, it is characterized by further improved image quality, greater compatibility in the PC area, as well as easier and more extensive processing options. The MPEG-4 format offers compared to MPEG-2 , in turn, a stronger compression, but requires greater processing power for playback or recording. MPEG-4 can also lead to quality losses due to compression artifacts .

PAL video

The Phase Alternating Line System (PAL system) is the television standard used in German-speaking countries. PAL was developed by Telefunken in 1963. It contains 625 scan lines per image (frame), 25 frames per second, corresponding to a duration of 40 ms / frame. The aspect ratio is 4: 3, so the pixels are not square to counter the resolution of 720 × 576 pixels (5: 4). PAL uses the YUV color model. The display is in interlace mode, so each image is divided into two fields, one with the even and one with the odd raster lines. Because of the picture gap, only 576 lines are visible. PAL is used in Brazil, China, Germany, Austria, Switzerland and India.

NTSC video

NTSC is the US television standard established in 1953 by the NTSC ( National Television Systems Committee ). NTSC contains 525 raster lines per picture, to be played back with exactly 29.97 pictures per second, corresponding to 33.37 ms per picture. Now and then you read 30 frames per second, but that is incorrect. The aspect ratio is 4: 3, the pixels are square. The display is in interlace mode, each image is divided into two fields, one with the even and one with the odd raster lines. At the beginning of each field, 20 raster lines are reserved, so a maximum of 485 raster lines remain for image information. Of these, however, only 480 are visible. Therefore, NTSC has a resolution of 640 × 480 pixels. NTSC uses the YIQ color model and is used in Japan, USA, Canada and Korea, among others.

Analog recording formats

VHS - Video Home System - was developed by JVC in the late 1970s. Thanks to a clever marketing strategy, it prevailed against more technically intelligent solutions such as Video 2000 worldwide. The magnetic tapes of the VHS cassettes are sensitive to interference. They are 1.27 cm wide. Video tape recording systems exist in many variants with different signal processing and different mechanical and [sic!] Tracking parameters. The peculiarity in the video sector consists on the one hand in the high upper limit frequency, which is approx. 5 MHz about 250 times higher than the audio signal, and on the other hand in the very low lower limit frequency close to 0 Hz. A high signal frequency can only be achieved at high relative speed . Therefore, video recorders work with rotating heads.

Digital video technology

The replacement of analog video technology towards digital processes was driven by graphic data processing. Powerful graphics cards enable PC users to render their own films and save them on digital systems. Digital signals obtained from analogue signals by this at regular intervals, samples ( samples taken), and the values of the numbers of samples are assigned to a finite range of numbers.

Format development

The recording technology and thus the formats have roughly developed in the following steps:

history

  • 1953: The first patent for the prototype of a video recorder is granted in Germany.
  • 1956: The first operational video tape recorder (VTR) for broadcast purposes from the Ampex company appears . The format was quadruplex .
  • 1964: The first commercial VTR, the Philips 3400, could record 45 minutes in black and white and cost 6900 DM.
  • 1969: The year of birth of home video: Philips and Grundig introduce the first recorder with an associated video camera, as well as the first video cassette recorder ( VCR system ) with new cassette technology . Up to now, the magnetic tapes were wound on open reels.
  • 1972: Sony introduces the first U-matic video cassette recorder.
  • 1976: JVC introduces the Video Home System (VHS) format, and Sony introduces the Betamax format .
  • 1980: Philips and Grundig introduce the Video 2000 system. In contrast to VHS and Betamax, Video 2000 cassettes were recorded on two sides and were superior to the other systems in terms of image quality. The format could not prevail, however, because VHS and Betamax were already too common.
  • 1984: The first camcorder with Video 8 cassettes is launched. Sony is the developer.
  • 1985: The first VHS cassette camcorder comes onto the market.
  • At the end of the 80s , VHS was developed into S-VHS and Video 8 into Hi8 .
  • The video CD was released in the early 90s with a playing time of 74 minutes in VHS quality.
  • 1995: The DVD standard is established. The first digital video (DV) and mini-DV camcorder appears.
  • 1996: The first DV recorder from Sony costs 8,000 DM.
  • 1999: The first Philips DVD recorder comes onto the market.
  • 2000: Hitachi's first DVD camcorder is introduced.
  • 2001: The DVD overtakes the VHS cassette in the commercial video sector.
  • 2003: The High Definition Video (HDV) format is considered the future home video format, but has so far only been used in Japan and the USA.
  • 2004: DVD recorders with hard drives largely replace VHS recorders.
  • 2005: HDV also becomes available in Europe.

See also

literature

Web links

Individual evidence

  1. ↑ See Duden online: Video , meaning 1 a.
  2. ↑ See Duden online: video technology , meaning 2.
  3. ↑ See Duden online: video technology , meaning 1.
  4. ↑ a b c d e Peter A. Henning: Pocket Book Multimedia . 4th edition. Hanser Verlag, 2007, ISBN 978-3-446-40971-2 , p. 179-184 .
  5. ↑ Ulrich Schmidt: Digital film and video technology . 2nd Edition. Hanser Verlag, 2008, ISBN 978-3-446-41250-7 , pp. 138 .
  6. ↑ Ulrich Schmidt: Digital film and video technology . 2nd Edition. Hanser Verlag, 2008, ISBN 978-3-446-41250-7 , pp. 109 .