hmp8112 Harris Corporation, hmp8112 Datasheet - Page 7

• Manufacturer Part Number: hmp8112
• Description: Ntsc/pal Video Decoder
• Manufacturer: Harris Corporation

internal decoding frequency of 4xf
The input sample rate converter will interpolate between
existing CLK samples to create the chroma locked (4xf
samples needed for the color decoder. An interpolation is
done to create the 4xf
applied..
The decoder can be used with the following video sources:
Analog Composite - NTSC M, - PAL B, D, G, H, I, N
Analog S - VHS (Y/C) - NTSC M, PAL B, D, G, H, I, N
Color Separation, And Demodulation
To separate the chrominance modulated color information
from the baseband luminance signal, a 2 line comb filter is
employed. In NTSC signals the color information changes
phase 180
VIDEO INPUT
DC RESTORE
HAGC
FIGURE 3. SAMPLE RATE CONVERSION
o
FIGURE 2A. PLL ACQUISITION MODE
from one line to the next. This interleaves the
OVERLAPPED CONTROL
INCOMING VIDEO SAMPLES
0
HSYNC
4xf
RESAMPLED VIDEO
And Special Combination PAL N
SC
SC
And Special Combination PAL N
pixel and a correction factor is then
t
SC
PW
.
= 2.0 s
TIME
TIME
HMP8112
SC
)
7
chrominance information at half line intervals throughout the
NTSC video spectrum. Therefore, NTSC has 227.5 cycles of
chrominance per NTSC line. The half of a cycle causes the
next reference burst to be 180
ous line’s burst. The two line comb efficiently removes the
chrominance information from the baseband luminance sig-
nal. When decoding NTSC, the decoder maintains full lumi-
nance bandwidth horizontally throughout the chrominance
carrier frequency range. Unlike most 2 line comb filter sepa-
ration techniques, vertical bandwidth is maintained by
means of a proprietary transform technique.
For PAL systems there are 283.75 cycles of chrominance
per line. Chrominance information is spaced at quarter line
intervals with a reference phase of 135
AMPLITUDE
AMPLITUDE
VIDEO INPUT
DC RESTORE
HAGC
FIGURE 4. COMPOSITE NTSC INTERLEAVE SCHEME
FIGURE 2B. PLL LOCKED MODE
START
TIME
0
HSYNC
Y
Y
TIME
END
6.5 s
f
FREQUENCY
FREQUENCY
H
o
/2
out of phase with the previ-
START
I, Q
I, Q
TIME
f
H
f
H
/2
o
. The reference
END
TIME
Y
Y