Philips Semiconductors
Preliminary specification
PAL/NTSC/SECAM video decoder with adaptive PAL/NTSC
comb filter, VBI-data slicer and high performance scaler
SAA7114H
8.3.3.2
Vertical scaler (subaddresses B0H to BFH and
E0H to EFH)
and field rate conversion are supported (i.e. de-interlacing,
re-interlacing).
Vertical scaling of any ratio from 64 (theoretical zoom) to
Figs 28 and 29 and Tables 12 and 13 are describing the
use of the offsets.
1
⁄
63 (icon) can be applied.
The vertical scaling block consists of another line delay,
and the vertical filter structure, that can operate in two
different modes. Called linear interpolation (LPI) and
accumulation (ACM) mode, controlled by
YMODE[B4H[0]].
Remark: The vertical start phase, as well as scaling
ratio are defined independently for luminance and
chrominance channel, but must be set to the same
values in the actual implementation for accurate
4 : 2 : 2 output processing.
• LPI mode: In Linear Phase Interpolation (LPI) mode
(YMODE = 0) two neighbouring lines of the source video
stream are added together, but weighted by factors
corresponding to the vertical position (phase) of the
target output line relative to the source lines. This linear
interpolation has a 6-bit phase resolution, which equals
64 intra line phases. It interpolates between two
consecutive input lines only. LPI mode should be
applied for scaling ratios around 1 (down to 1⁄2), it must
be applied for vertical zooming.
The vertical processing communicates on it’s input side
with the line FIFO buffer. The scale related equations are:
• Scaling increment calculation for ACM and LPI mode,
down-scale and zoom:
Nline_in
Nline_out
YSCY(C)[15:0] = lower integer of 1024 ×
------------------------
• BCS value to compensate DC gain in ACM mode
(contrast and saturation have to be set):
CONT[7:0]A5H[7:0] respectively SATN[7:0]A6H[7:0]
• ACM mode: The vertical Accumulation (ACM) mode
(YMODE = 1) represents a vertical averaging window
over multiple lines, sliding over the field. This mode also
generates phase correct output lines. The averaging
window length corresponds to the scaling ration,
resulting in an adaptive vertical low-pass effect, to
greatly reduce aliasing artefacts. ACM can be applied
for down-scales only from ratio 1 down to 1⁄64. ACM
results in a scale dependent DC gain amplification,
which has to be precorrected by the BCS control of the
scaler part.
Nline_out
= lower integer of
= lower integer of
× 64 , or
------------------------
Nline_in
1024
× 64
------------------------------
YSCY[15:0]
8.3.3.3
Use of the vertical phase offsets
As shown in Section 8.3.1.3, the scaler processing may
run randomly over the interlaced input sequence.
Additionally the interpretation and timing between ITU 656
field ID and real-time detection by means of the state of
H-sync at falling edge of V-sync may result in different field
ID interpretation.
The phase and scale controlling DTO calculates in 16-bit
resolution, controlled by parameters
YSCY[15:0]B1H[7:0]B0H[7:0] and
YSCC[15:0]B3H[7:0]B2H[7:0], continuously over the
entire filed. A start offset can be applied to the phase
processing by means of the parameters
YPY3[7:0] to YPY0[7:0] in BFH[7:0] to BCH[7:0] and
YPC3[7:0] to YPC0[7:0] in BBH[7:0] to B8H[7:0]. The start
phase covers the range of 255 32 to 1⁄32 lines offset.
⁄
Also a vertically scaled interlaced output gets a larger
vertical sampling phase error, if the interlaced input fields
are processed, without regarding the actual scale at the
starting point of operation (see Fig.28).
Four events are to be considered, they are illustrated in
Fig.29.
By programming appropriate, opposite, vertical start
phase values (subaddresses B8H to BFH and
E8H to EFH) depending on odd/even field ID of the source
video stream and A/B-page cycle, frame ID conversion
2000 Mar 15
48
NXP [ NXP ]
