Video decoder

This article is about decoding analog video signals. For digital video compression decoders, see video codec.

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. 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

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