Video decoder

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A video decoder is an electronic circuit, often contained within a single integrated circuit chip, that converts base-band analog video signals to digital components video.[1] Video decoders commonly allow programmable control over video characteristics such as hue, contrast, and saturation. A video encoder performs the inverse function of a video decoder; it converts raw (uncompressed) digital video to analog video.

The input signal to a video decoder is analog video (composite or S-Video) that conforms to a standard format such as NTSC or PAL. The output digital video may be formatted in various ways, such as 8-bit or 16-bit 4:2:2, 12-bit 4:1:1, or BT.656. Usually, in addition to the digital video output bus, a video decoder will also generate a clock signal and other signals such as:

  • Sync — indicates the beginning of a video frame
  • Blanking — indicates video blanking interval
  • Field — indicates whether the current video field is even or odd
  • Lock — indicates the decoder has detected and is locked (synchronized) to a valid analog input video signal

Functional blocks[edit]

The main functional blocks of a video decoder typically include these:

  • Analog processors
  • Y/C (luminance/chrominance) separation
  • Chrominance processor
  • Luminance processor
  • Clock/timing processor
  • A/D converters for Y/C
  • Output formatter
  • Host communication interface


  1. ^ Jack, Keith (1996). Video demystified : a handbook for the digital engineer (2nd ed.). San Diego, CA: HighText Interactive. p. 233. ISBN 1-878707-23-X.