Video decoder
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 decoder performs the inverse function of a video encoder, which converts raw (uncompressed) digital video to analog video.
Signals
The input signal to a video decoder is analog video that conforms to a standard format. For example, a standard definition (SD) decoder accepts (composite or S-Video) that conforms to SD formats such as NTSC or PAL. High definition (HD) decoders accept analog HD formats such as AHD, HD-TVI, or HD-CVI.
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, BT.656 (SD) or BT.1120 (HD). 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 (applies to interlaced formats)
- Lock — indicates the decoder has detected and is locked (synchronized) to a valid analog input video signal
Functional blocks
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
References
- ^ 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.
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