ML6426
TYPICAL APPLICATIONS
RECONSTRUCTION FILTER SELECTION FOR HDTV AND
VGA SIGNAL FILTERING
The filtering requirements for HDTV and VGA standards
vary depending on the resolution of the image to be
displayed, and its refresh rate. The actual refresh rate of
the display is not necessarily the same as the transmission
rate of the frames of images. Some formats use a frame
rate of 30Hz, but the display of those formats cannot be
scanned onto the CRT at 30Hz. Excessive large area
flicker would result. Such kinds of flicker can be seen on
a PAL display with its brightness set high. To avoid this,
the video will need to be stored in a frame buffer. This
buffer already exists in the MPEG decoder of HDTV
systems, so there is no cost penalty. The buffer is read out
at twice the rate as the frame rate for 30Hz systems, thus
getting us a refresh rate of 60Hz. Similar things are done
for the 24Hz frame rate formats to boost them to a 60Hz
refresh rate.
PIXELS
1920
1280
704
640
P=progressive scan, I=interlaced scan
VERTICAL LINES
1080
720
480
480
ASPECT RATIO
16:9
16:9
16:9 and 4:3
4:3
PICTURE TRANSMISSION RATE
60I, 30P, 24P
60P, 30P, 24P
60P, 60I, 30P,24P
60P, 60I, 30P,24P
Table 1: HDTV / Advanced TV Applications: (From Table 10.3 from ATSC document A54)
APPROXIMATE
RECONSTRUCTION
FILTER CUTOFF
PICTURE
TRANSMISSION
RATE
(Note 2)
SMPTE
274M
1920
1920
1080
1080
720
480
(Note 1)
480
480
(Note 1)
480
VERTICAL
LINES
PIXELS
60I
30P, 24P
60P, 30P,
24P
60I
60P, 30P,
24P
60I
60P, 30P,
24P
60Hz
60Hz
60Hz
60Hz
60Hz
60Hz
60Hz
35.3KHz
70.6KHz
47.1KHz
15.7KHz
31KHz
15.7KHz
31KHz
81MHz
162MHz
60MHz
13.5MHz
27MHz
24.5MHz
12.27MHz
40.5MHz
81MHz
30MHz
6.75MHz
13.5MHz
12MHz
6MHz
ML6426-6
N/A
ML6426-5
ML6426-4
ML6426-1
ML6426-2
ML6426-4
ML6426-2
ML6426-1
SMPTE
1280
704
704
640
640
P=progressive scan, I=interlaced scan, na = not available
Note 1:
NTSC display rates, can be fed directly into NTSC encoder (set top box)
Note 2:
60 Hz also includes 59.94Hz
Note 3:
custom frequencies ranging ± 3 to 6MHz can be special cut to order
Table 2: Choosing the Correct Reconstruction Filter and Video Amplifier for TV Applications, ML6426 options
MICRO LINEAR
FILTER TO USE
(Note 3)
APPROXIMATE
HORIZONTAL
RATE
APPROXIMATE
SAMPLE
CLOCK
DISPLAY
REFRESH
RATE
(Note 2)
STANDARD
November, 1999
7
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
