Video decoder
A video decoder is an
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
4:1:1, 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
RGB and YCbCr. Together, these steps constitute video decoding because they "decode" an analog video format such as NTSC or PAL
.
References
- ISBN 1-878707-23-X.
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