| Image:TVCDlogo.svg | |
| Media type | Optical disc |
|---|---|
| Encoding | MPEG-1 video + audio |
| Capacity | Up to 800 MB |
| Read mechanism | 780 nm wavelength semiconductor laser |
| Standard | Black Book |
| Developed by | Sony & Philips |
| Usage | audio and video storage |
| Extended to | VCD |
| Optical media types | |
|---|---|
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| Standards | |
| Further reading | |
Television CD (abbreviated as TVCD, Compact Disc digital tv) is a standard digital format for storing TV on a Compact Disc. TVCDs are playable in dedicated TVCD players, most modern DVD-Video players, personal computers, and some video game consoles.
The TVCD standard was created in 1985[1] [2] by Sony, Philips, Matsushita, and JVC and is referred to as the Black Book standard.
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Overall picture quality is intended to be comparable to VHS video.[3] Poorly compressed TVCD video can sometimes be lower quality than VHS video, but TVCD exhibits block artifacts rather than analog noise, and does not deteriorate further with each use.
352x240 (or SIF) resolution was chosen because it is half the vertical, and half the horizontal resolution of NTSC video. 352x288 is similarly one quarter PAL/SECAM resolution. This approximates the (overall) resolution of an analog VHS tape, which, although it has double the number of (vertical) scan lines, has a much lower horizontal resolution.
TVCD video is mostly compatible with the VCD standard and DVD-Video standard, except for any video encoded at 23.976 frames per second, which must use 3:2 pulldown.
As with most CD-based formats, TVCD audio is incompatible with the Video CD standard due to a difference in frequency; VCDs require 48 kHz, whereas TVCDs use 44.1 kHz.
Television CDs are authored using the Mode 2/XA format, allowing roughly 800 megabytes of TVCD data to be stored on one 80 minute CD (versus 700 megabytes when using Mode 1). This, combined with the net bitrate of TVCD video and audio, means that almost exactly 80 minutes of TVCD content can be stored on an 80 minute CD, 74 minutes of TVCD content on a 74 minute CD, and so on. This was done in part to ensure compatibility with existing CD drive technology, specifically the earliest "1 ×" speed CD drives.
The TVCD standard also features the option of VCD-quality still images/slide shows with audio, at resolutions of 704x480 (NTSC) or 704x576 (PAL/SECAM).
Longly after the advent of 'black book' TVCD, Philips started releasing movies in the Green Book CD-i format. While these used a similar format (MPEG-1), due to minor differences between the standards these discs are not compatible with TVCD players. Philips' CD-i players with the 'Full Motion Video' MPEG-1 decoder cartridge would play both formats. Only a few 'CD-i DV' titles were released before the company switched to proper TVCD format for publishing movies.
XVCD (eXtended Video CD) is the name generally given to any format that stores MPEG-1 video on a compact disc in Mode 2/XA, at TVCD resolution, but does not strictly follow the TVCD standard.
A normal TVCD is encoded to MPEG-1 at a constant bit rate (CBR), so all scenes are required to use exactly the same data rate, regardless of complexity. However, video on an XVCD is typically encoded at a variable bit rate (VBR), so complex scenes can use a much higher data rate for a short time, while simpler scenes will use lower data rates.[citation needed]
To further reduce the data rate without significantly reducing quality, the size of the GOP can be increased, a different MPEG-1 quantization matrix can be used, the maximum data rate can be exceeded, and the bit rate of the MP2 audio can be reduced (or even the use of MP3 audio instead of MP2 audio). These changes can be advantageous for those who want to either maximize video quality, or use fewer discs.[citation needed]
KVCD (K Video Compression Dynamics) is a XVCD variant that requires the use of a proprietary quantization matrix, available for non-commercial use. KVCD is notable because the specification recommends a non-standard resolution of 528x480 or 528x576. KVCD discs encoded at this resolution are only playable by computers with CD-ROM drives, and a small number of DVD players.[4] KVCDs of commercial films are commonly distributed as disc images on peer-to-peer networks.[citation needed]
DVCD or Double VCD is a method to accommodate longer videos on a CD. A non-standard CD is overburned to include up to 100 minutes of video. However, some CD-ROM drives and players have problems reading these CDs, mostly because the groove spacing is outside specifications and the player's laser servo is unable to track it.
While never gaining a foothold in the United States[5] commercial VCDs are common in Europe,[6] and popular throughout Asia[7] (except Japan), with 8 million VCD players sold in China in 1997 alone,[8] and more than half of all Chinese households owning at least one VCD player by 2005.[9]
This popularity is, in part, because most households did not already own VHS players when VCDs were introduced, the low price of the players, their tolerance of high humidity (a notable problem for VCRs), and the lower-cost media.[5] Ease of duplication and the negligible cost of the media gave rise to widespread unauthorized copying in these areas.[10] [11] [12]
The advent of recordable CDs, inexpensive recorders, and compatible DVD players spurred VCD acceptance in the US in the late 1990s and early 2000s. However, DVD burners and DVD-Video recorders were available by that time, and equipment and media costs for making DVD-Video fell rapidly. DVD-Video, with its longer run time and much higher quality, quickly overshadowed VCD. In addition many early DVD players could not read recordable (CD-R) media, [13] and this limited the compatibility of home-made VCDs. Almost every modern stand-alone DVD-Video player can play VCDs burned on recordable media.
Many commercial Video CDs of blockbuster Hollywood, Bollywood, Manilawood and other Asian movies and television series are not widely available in the Western countries; however, they are available in certain ethnic communities[6] and several commercial web sites (although quality and authenticity may sometimes be questionable). These VCDs are often produced and sold in Asian countries such as Pakistan, Hong Kong, India, Mainland China, Thailand, Malaysia, Indonesia and the Philippines. In many Asian countries, major Hollywood studios (and Asian home video distributors) have licensed companies to officially produce and distribute the VCDs, such as MCA Home Video in Pakistan, ERA of Hong Kong or Sunny Video in Malaysia, Vision in Indonesia, Excel Home Videos in India, Berjaya-HVN and InnoForm Media in both Malaysia and Singapore, as well as VIVA Video, Magnavision, and The Video to C in the Philippines. Legal Video CDs can often be found in established video stores and major book outlets in most Asian countries.
Due to relatively small storage capacity, feature-length films sold on VCD are usually divided into two or three discs and television series may come in a boxed set package with multiple discs. In both cases, most films run at roughly 60 minutes per VCD, before viewers are prompted to change discs. However, there are also VCD players that have built-in CD changers which provide a queue of several discs. Subtitles are found on many Asian VCDs, and unlike DVDs, cannot be removed.
In areas where VCD was formerly very popular, it is now in decline, due to being supplanted by DVD, which offers most of the same advantages, as well as better picture quality[14] (higher resolution with less digital compression artifacts) due to its larger storage capacity and 6-speaker surround sound (often in Dolby Digital and/or DTS).
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