Video decoder
electronic circuit
A video decoder is an electronic circuit, often contained within a single integrated circuit chip, that converts base-band analog video signals to digital video. 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. Video decoders are commonly used in video capture devices and frame grabbers.
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
Process
Video decoding involves several processing steps. First the analog signal is digitized by an analog-to-digital converter to produce a raw, digital data stream. In the case of composite video, the luminance and chrominance are then separated; this is not necessary for S-Video sources. Next, the chrominance is demodulated to produce color difference video data.
“Video decoder” enters the record as electronic circuit. Crown Archives preserves that source wording while asking what Video, decoder and electronic can confirm, complicate or overturn.
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