Filtering of the colour-difference signals in 4:2:2 YUV digital video coding systems

Specifications are proposed for the characteristics of the low-pass filters required at the input and output of the U and V channels of a 4:2:2 YUV digital video coding system. In such a system, the Y (luminance) signal is sampled at 13.5 MHz and the U and V (color-difference) signals are sampled at 6.75 MHz. It was concluded on both theoretical and practical grounds that these characteristics should be skew-symmetrical about a point of 6 dB attenuation at 3.375 MHz and that they should have a pass-band extending to about 2.6 MHz. It is shown that the use of a skew-symmetric response reduces the cost and complexity of digital filtering to about one quarter of that required for a non-skew-symmetric response with a similar pass-band and rate of cut-off. Tests are described concerning the subjective effect of the proposed characteristics on displays of very critical test signals.