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# MPEG2: the "gold standard" of image compression

Even with the fine track pitch and fine pits, which give a tremendous boost to storage capacity, an entire movie can't be stored on one side of a 12cm disc without powerful image-compression technology.

Use of compression technology is already widespread in the audio field where MiniDiscs, for example, rely on it, and it is making inroads in PC applications. But, compared with audio, image information is vastly more data-intensive. Global standards for image-compression technology are promoted by the Moving Picture Experts Group. Building on the success of the MPEG1 standard, the more sophisticated MPEG2 standard has been introduced. The DVD is MPEG2-compliant.

MPEG2 employs the variable bit rate method whereby the data rate varies according to the information content of the image. To achieve consistently superior picture quality, the data rate is reduced for images with low information content and increased for images with higher content.

DVD-Video specifications regarding image and audio

Image Max. 1 stream

# MPEG2 (variable bit rate)
   TV system with 525/60
    (NTSC)
   TV system with 625/50
    (PAL)


Audio Max. 8 streams (Use of
  5.1ch is possible for
  each stream.)

# Linear PCM compatible
   (16/20/24 bit,
   48/96kHz)

# Dolby AC-3
   (digital compression)* 1
   5.1ch digital surround
   compatible

# MPEG2 audio playback
  (MPEG1 compatible)* 2


Sub-Picture Max. 32 streams

# Run-length coded BitMap
  (2-bit/pixel)

  Standard size:
    720 * 480 dots (NTSC)
    720 * 576 dots (PAL)   (Use of 16-color pallet
   is possible)



*1
Standard for NTSC players. Optional for PAL players, depending on the manufacturer.

*2
Standard for PAL players. Optional for NTSC players, depending on the manufacturer.



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