Datasheet

15
SLES084C − August 2007 TVP5146
2.2.3 Luminance Processing
The digitized composite video signal passes through either a luminance comb filter or a chroma
trap filter, either of which removes chrominance information from the composite signal to
generate a luminance signal. The luminance signal is then fed into the input of a peaking circuit.
Figure 2−12 illustrates the basic functions of the luminance data path. In the case of S-video, the
luminance signal bypasses the comb filter or chroma trap filter and is fed directly to the circuit.
High-frequency components of the luminance signal are enhanced by a peaking filter
(sharpness). Figure 2−13, Figure 2−14, and Figure 2−15 show the characteristics of the peaking
filter at four different gain settings that are programmable via the host port.
Bandpass
Filter
x
Gain
Peaking
Filter
IN
+
OUT
Delay
Peak
Detector
Figure 2−12. Luminance Edge-Enhancer Peaking Block Diagram
f – Frequency – MHz
−1
0
1
2
3
4
5
6
7
01234567
Gain = 0
Gain = 2
Gain = 1
Gain = 0.5
Peak at
f = 2.40 MHz
Amplitude − dB
f – Frequency – MHz
−1
0
1
2
3
4
5
6
7
01234567
Gain = 0
Gain = 2
Gain = 1
Gain = 0.5
Peak at
f = 2.64 MHz
Amplitude − dB
Figure 2−13. Peaking Filter Response, NTSC
Square Pixel Sampling
Figure 2−14. Peaking Filter Response,
NTSC/PAL ITU-R BT.601 Sampling