DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

1125/25
1125/24
S TL
1125
1125
2640
2750
1080
2200
1920
74.25 MHz 16:9
Figure 13.3 HDTV rasters at 24 Hz and 25 Hz carry an array of 1920×1080 active samples, using
a 74.25 MHz sampling rate at the interface. For 24 Hz (1080p24), the 1920×1080 array is carried
in an 1125/24 raster. For 25 Hz, the array is carried in an 1125/25 raster.
24
1. 001
≈
23. 976
progressive segmented frame (PsF) scheme that
I introduced on page 62.
Some European video engineers dislike 1125 lines, so in
addition to the approach sketched in Figure 13.3 an
alternative approach is standardized in SMPTE 295M:
The 1920×1080 image is placed in a 1250/25/2:1 raster
with 2376 S TL . I recommend against this approach:
Systems with 1125 total lines are now the mainstream.
For 24 Hz, 1125 total lines are retained, and S TL is
increased to 2750 achieve the 24 Hz frame rate. This
yields the 1080p24 format, in an 1125/24 raster. This
system is used in emerging digital cinema (D-cinema)
products. A variant at 23.976 Hz is accommodated.
In Sony’s HDCAM system, the 1920×1080 image is
downsampled to 1440×1080, and color differences are
subsampled 3:1:1, prior to compression. This is an
internal representation only; there is no corresponding
uncompressed external interface standard.
CHAPTER 13 INTRODUCTION TO HDTV 115