TW2864D datasheet(14/110 Pages) RENESAS

14 / 110 page

TW2864

FN7745 Rev. 0.00

Page 14 of 110

September 28, 2012

Y/C Separation

The color-decoding block contains the luma/chroma separation for the composite video signal and multi-standard

color demodulation. For NTSC and PAL standard signals, the luma/chroma separation can be done either by comb

filter or notch/band-pass filter combination. For SECAM standard signals, adaptive notch/band-pass filter is used. The

default selection for NTSC/PAL is comb filter.

In the case of comb filter, the TW2864 separates luma (Y) and chroma (C) of a NTSC/PAL composite video signal

using a proprietary 4H adaptive comb filter. The filter uses a four-line buffer. Adaptive logic combines the upper-comb

and the lower-comb results based on the signal changes among the previous, current and next lines. This technique

leads to excellent Y/C separation with small cross luma and cross color at both horizontal and vertical edges

Due to the line buffer used in the comb filter, there is always two lines processing delay at the output except for the

component input mode which has only one line delay.

If notch/band-pass filter is selected, the characteristics of the filters are shown in the filter curve section.

Figure 3 shows the frequency response of notch filter for each system NTSC and PAL. Figure 4 shows the frequency

response of Chroma Band Pass Filter Curves.

x 10

-45

-40

-35

-30

-25

-20

-15

-10

-5

Frequency (Hertz)

NTSC

PAL

FIGURE 3. THE CHARACTERISTICS OF LUMINANCE NOTCH FILTER FOR PAL

TW2864D Datasheet(PDF) 14 Page - Renesas Technology Corp