
L64005 MPEG-2 Audio/Video Decoder Technical Manual
1-13
Final Rev F
Copyright 1996 by LSI Logic Corporation. All rights reserved.
recode at the original lm rate. For example, lm material at 24 pictures
per second may have been digitized and converted to a 30 frame-per-
second system by the technique of 3:2 pull-down. In this mode, digitized
pictures are shown alternately for three and for two television eld times.
A television eld time is 60 elds per second.
In order for video at 30 frames per second to be shown at the television
eld rate, each frame is simply shown for two television eld times. How-
ever, to display 24 frame-per-second video at the television frame rate,
3:2 pull-down is necessary. A single frame of 24 frame per second video
is repeated three times at the television eld rate, followed by the next
frame repeated two times. This pattern of three and then two repeated
frames continues. The net result is that a total of two frames of 24 frame-
per-second video is displayed over a period of ve television eld times,
or 5/60ths (1/12th) of a second. This result is exactly the same amount
of time occupied by two frames of 24 frame per second video
. Therefore 3:2 pull-down allows video digitized at 24
frames per second to be displayed at the television eld rate with no jerk-
iness or loss of synchronization.
ADPCM. Adaptive Differential Pulse Code Modulation. A type of DPCM
in which the algorithm dynamically adjusts to the content of the data
being encoded.
B-Channel. ISDN communications channel carrying 64 Kbit/s.
CCIR. Consultative Committee for International Radio.
CCIR601. Recommendation for digital video (4:2:2, 720 samples per
line). Also recommends chromaticity for YCrCb color space.
CCITT. International Telegraph and Telephone Consultative Committee.
Renamed ITU-TSS.
CD-ROM. Compact Disk Read-Only Memory.
CD-ROM XA. CD-ROM extended architecture (species ADPCM
qualities).
CMYK. Cyan, Magenta, Yellow, Black. These colors are used in the print-
ing industry.
Chrominance. The color information portion of a signal (UV portion of
YUV). See YUV.
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