Video CD

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Video CD or VCD is a standard for saving video data on a compact disc to them (VCD players on special playback equipment CD-i -Spielern and most DVD players ) in conjunction with a television or personal computers play . Video CD files can be recognized by the .dat file extension .

Technical details

The VCD standard was agreed in 1993 by a consortium of Japanese electronics manufacturers and recorded in the so-called White Book . It is one of the official CD formats that are allowed to carry the compact disc logo - in this case compact disc digital video . It describes the storage of video data according to the MPEG-1 standard on a standard CD. The resolution specified in the standard is 352 × 288 pixels with 25 frames per second for PAL , 352 × 240 pixels with 29.97 or 23.976 frames per second for NTSC . The aspect ratio is 4: 3 . 16: 9 is not provided. The sound is stereo. Joint stereo, digital surround sound, multiple audio tracks or selectable subtitles are not possible on VCDs; mono sound must be implemented using identical left and right audio tracks, if required, as with audio CDs. So the data is saved twice. The bit rate must be a maximum of 1,151,929 bit / s for the image data, exactly 224,000 bit / s for the stereo sound data (in MP2 format) and exactly 1,411,200 bit / s for the entire data. The latter corresponds to the bit rate of audio CDs ; thus the maximum running time is identical and VCD players can use the same drive mechanism as normal CD players. Variable bit rates are not provided. Playback software for CD-i players must be stored on a standard-compliant video CD, as they have no built-in software. This software costs just under a minute to run.

Picture and sound quality

The picture quality corresponds roughly to that of a VHS video , but is somewhat worse than that of a high-quality VHS cassette recorded with good professional recording equipment. The VHS-typical image and color noise does not apply, but blurring, compression artifacts ("blocks", ring formation around objects) and jerky movements can be seen on video CDs . The sound quality is much better than VHS edge track sound, but often worse than HiFi VHS. The image quality fluctuates depending on the encoding software used and its settings, but cannot exceed a certain maximum. Because of this and the maximum playing time of originally just over 73 minutes (later approx. 79 minutes when using a 700 MB CD-R ), VCDs are only of limited suitability as a medium for feature films.

Another disadvantage of the Video CD is the reduced vertical resolution (288 or 240 visible lines) compared to the TV full resolution (576 visible lines in Europe, 480 in America). H. every second raster line is "thrown away", whereby the interlacing of the original signal and thus the time resolution is lost. Many analog video formats, such as. B. VHS do not have this property due to the system.

For some years now, there has been a non-standard VCD variant for DVD players called MVCD , also known as KVCD , TVCD , AVCD or generally called xVCD . This offers u. a. by a modified quantization - matrix increased playing time and some slightly better image quality, but is not not playable on any DVD player and video-only CD players functional.

specification

Video

Video specification

Although many DVD players also support the playback of VCDs, VCD Video is only compatible with the DVD-Video standard if it is encoded at 29.97 or 25.00 frames per second. The resolutions 352 × 240 and 352 × 288 ( SIF ) were chosen because they correspond to half the horizontal and vertical resolution of NTSC and half the horizontal resolution of PAL. This corresponds to about half the resolution of an analog VHS video which has a resolution of 330 horizontal and 480 vertical pixels (PAL: 330 × 576).

Audio

Audio specification

As with most CD-based formats, VCD Audio is not compatible with the DVD-Video standard because of the differences in sampling frequency (DVDs require 48 kHz and VCDs are 44.1 kHz).

distribution

Before VCDs were widespread in Europe and America, they were very popular in Asia; Many VCD recorders were also sold there, with which CD-R blanks can be recorded as VCDs. The reasons were the considerably simpler and more robust mechanics in relation to VHS, low prices for playback devices and media, as well as the much lower sensitivity to high humidity compared to VHS tapes; VHS tapes are often infested with mold, especially in Southeast Asia. The low cost of VCD media and the lack of copy protection allowed commercially distributed illegal copies to proliferate in this area. This is probably why this standard has never been heavily endorsed by industry in the United States . The later availability of rewritable CD-RWs and cheap CD recorders has led to the rapid spread of privately burned video CDs, especially since they can also be played by most DVD players.

The expanded standard and thus the successor is the SVCD (Super Video Compact Disc). It is based on MPEG-2 compression and supports variable data rates. In this way, an increased picture quality is achieved compared to the VCD with its MPEG-1 compression, but at the expense of an even shorter running time.

With the advent of DVD burners for the mass market, the VCD has been increasingly replaced by the DVD for private recordings . This has the most advantages for customers compared to the VCD. In addition, there is the considerably better picture and sound quality as well as an increased playback time.

See also

Individual evidence

  1. ↑ http://home.uni-leipzig.de/horst-rothe/vidlexik.htm
  2. ↑ a b MPEG1 Specifications . In: icdia.co.uk .