Philips Semiconductors
Video In
File: vin.fm5, modified 7/24/99
PRELIMINARY INFORMATION
6-9
6.4
HALFRES CAPTURE MODE
Halfres capture mode is identical in operation to fullres
capture mode except that horizontal resolution is re-
duced by a factor of two on both luminance and chromi-
nance data.
grammed to capture HEIGHT lines of WIDTH pixels in
halfres mode, the resulting captured planar data is as
WIDTH/4 chrominance samples are captured. In this
mode, START_X and WIDTH must be a multiple of four.
Horizontal-resolution reduction is performed as shown in
ventions of the pixels in memory depends on the SC
(Sampling Convention) bit in the VI_CTL register. As-
suming that the camera sampling positions obey the con-
ventions shown in
Figure 6-5, two possible spatial for-
mats are supported in memory:
If SC=0, co-sited luminance and chrominance sam-
sponds
to
the
standard YUV
4:2:2
sampling
conventions.
If SC=1, interspersed chrominance samples result,
subsampling of the chroma components) identical to
the MPEG-1 sampling conventions. If vertical sub-
sampling is desired, it can either be performed in
software on the DSPCPU, or in hardware using the
Image Coprocessor (ICP).
The filtering process applies mirroring at the edge of the
For both filters, computed video data is clamped to 01h if
result of the filter is less than 01h and clamped to FFh if
greater than FFh.
6.5
RAW CAPTURE MODES
All raw capture modes (raw8, raw10s and raw10u) be-
have similarly. VI_DATA information is captured at the
rate of the sender’s clock, without any interpretation or
start/stop of capture on the basis of the data values. Any
clock cycle in which VI_DVALID is asserted leads to the
capture of one data sample. Samples are eight or 10 bits
long (raw8 versus raw10 modes). For the eight-bit cap-
ture mode, four samples are packed to a word. For the
10-bit capture modes, two samples (of 16 bits each) are
packed to a word. The extension from 10 to 16 bits uses
sign extension (raw10s) or zero extension (raw10u).
YUV 4:2:2 CCIR656
input samples
a
bcd
e
f
g
h
i
j
k
l
Halfres capture
sample results
U
f
'
3
U
c
–
19
U
e
19
U
g
3
U
i
–
++
() 32
=
V
f
'
3
V
c
–
19
V
e
19
V
g
3
V
i
–
++
() 32
=
Y
h
'
3
Y
e
–
19
Y
g
32
Y
h
19
Y
i
3
Y
k
–
++
+
() 64
=
Figure 6-13. Halfres co-sited sample capture.
YUV 4:2:2 CCIR656
input samples
a
bcd
e
f
g
h
i
j
k
l
Halfres capture
sample results
Y
g
'
3
Y
d
–
19
Y
f
32
Y
g
19
Y
h
3
Y
j
–
++
+
() 64
=
U
f
'
3
U
c
–
19
U
e
19
U
g
3
U
i
–
++
() 32
=
V
f
'
3
V
c
–
19
V
e
19
V
g
3
V
i
–
++
() 32
=
Figure 6-14. Halfres interspersed sample capture.