Chrominance Processing

The following sections show the functional blocks used for chrominance processing.

Automatic Color Gain

The automatic color gain restores the nominal chrominance levels. The gain range extends from -6 dB (attenuation by a factor of 2) up to +30 dB (amplification by a factor of 32). The automatic color gain is always enabled.

Color Killer

Automatic color killer disables the chrominance decoding when the incoming video signal is a black-and-white signal, or when the incoming signal is very weak or noisy.

You can configure the automatic color killer through the Virtual File System API.

Color Saturation Control

You can adjust color saturation by applying gain on chrominance component through the Saturation element. his color saturation control can be used at anytime, even during acquisition. The decoder provides a luminance gain adjustment in 256 steps, ranging from 0 up to 200 %, with a default value of 100 %.

Output Range Limiting

The chrominance components U and V are delivered in 8-bit digital codes, according to ITU-R BT.601-4 specification. The chrominance spans over 225 levels in the center part of the [0..255] scale, with zero signal corresponding to 128 (0x80). The nominal range of chrominance levels is 16 (0x10) up to 240 (0xF0).

The chrominance output range is bounded in the decoder. The lowest value for a chrominance component is 2. The highest value for a chrominance component is 254 (0xFE).

V16H264ChrominanceOutputRange

ITU-R BT.601-4 chrominance output range

The chrominance output range is normally bounded in the range [2..254]. The darkest chrominance levels will not produce a chrominance output code below 2. The brightest chrominance levels will not produce a chrominance output code above 254 (0xFE).

Hue Control

The hue control is always fixed to 0 %.

Color Transition Improvement Control

CTI gain is always set at 75 %.

Chrominance Coring

The coring is always set to 128 ± 2. This means that chrominance codes 126, 127, 129 and 130 are substituted by chrominance code 128.