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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 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. 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. At this point, the data may be modified so as to adjust brightness, contrast, saturation and hue. Finally, the data is transformed by a color space converter to generate data in conformance with any of several color space standards, such as RGB and YCbCr. Together, these steps constitute video decoding because they "decode" an analog video format such as NTSC or PAL.

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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[VideoDemystified-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.

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@@ Line 1: / Line 1: @@
+{{About|decoding analog video signals|digital video compression decoders|video codec}}
-A '''video decoder''' is an electronic circuit, often contained within a single integrated circuit chip, that converts base-band analog video signals (e.g., NTSC, PAL) to digital components video. Video decoders commonly allow programmable control over video characteristics such as hue, contrast, and saturation. In contrast, a '''video encoder''' performs the inverse function of a video decoder; it converts raw (uncompressed) digital video to analog video.
+[[File:SAA7114H video decoder by Philips-3610.jpg|thumb|Integrated circuit video decoder (Philips SAA7114H)]]
+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.<ref name=VideoDemystified>{{cite book|last1=Jack|first1=Keith|title=Video demystified : a handbook for the digital engineer|date=1996|publisher=HighText Interactive|location=San Diego, CA|isbn=1-878707-23-X|page=233|edition=2nd}}</ref> Video decoders commonly allow programmable control over video characteristics such as [[hue]], [[contrast (vision)|contrast]], and [[colorfulness|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 device]]s and [[frame grabber]]s.
+==Signals==
-The input signal to a video decoder is analog 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 8-bit ITU-R BT.656. Usually, in addition to the digital video outputs, a video decoder will also generate and output synchronization, blanking, field, lock, and clock 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 video|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]], [[ITU-R BT.656|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:
+* [[Frame synchronization (video)|Sync]] — indicates the beginning of a video frame
+* [[blanking (video)|Blanking]] — indicates video blanking interval
+* [[field (video)|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==
@@ Line 15: / Line 26: @@
 * 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. At this point, the data may be modified so as to adjust brightness, contrast, saturation and hue. Finally, the data is transformed by a [[color space]] converter to generate data in conformance with any of several color space standards, such as [[RGB]] and [[YCbCr]]. Together, these steps constitute ''video decoding'' because they "decode" an analog video format such as [[NTSC]] or [[PAL]].
 ==References==
+{{reflist}}
 {{Electronics-stub}}
 [[Category:Electronic circuits]]