tm1300 NXP Semiconductors, tm1300 Datasheet - Page 118

• Manufacturer Part Number: tm1300
• Description: Tm-1300 Media Processor
• Manufacturer: NXP Semiconductors

TM1300 Data Book
The equations for the blending are illustrated below.
7.15.2
If the EVO_ENABLE and KEY_ENABLE bits are set to
‘1’ in EVO_CTL the TM1300 activates chroma keying.
The graphics overlay is taken from a pixel-packed YUV
4:2:2+ data structure in memory. The EVO_KEY regis-
ter provides the value which signifies full transparency
for the overlay. The overlay values (Y, U and V) are com-
pared to the values stored in bit-fields of the EVO_KEY
register. EVO_KEY has three 8-bit fields: KEY_Y,
KEY_U and KEY_V, which store the values to be com-
pared to the Y, U, and V components, respectively, of the
overlay for chroma keying. Bits that correspond to bits
set in MASK_Y and MASK_UV are ignored for the com-
parison. When there is an exact match between the pixel
value and the value in EVO_KEY (disregarding any bits
masked by MASK_Y and MASK_UV), then the overlay
value is not present in the output stream, resulting in full
transparency.
The mask bits in EVO_MASK provide for varying de-
grees of precision in the chroma-key matching process.
The EVO_MASK.MASK_Y field can mask from 0 to 4
LSBs of the overlay Y component during the chroma key
process. For example, setting MASK_Y = 1 eliminates
the influence of the LSB of KEY_Y in the keying process.
This can be used to widen the range of key matching to
account for irregularities in the chroma-key video signal.
Likewise, EVO_MASK.MASK_UV is used to mask from
zero to four LSBs of the overlay U and V components
during the chroma key process. For example, setting
MASK_UV = 1 eliminates the influence of the LSB of
KEY_U and KEY_V in the keying process.
7.15.3
If EVO_CTL.CLIPPING_ENABLE = 1 the EVO performs
fully-compliant programmable clipping. Clipping is per-
formed as the last step of the video pipeline, after chro-
ma keying and alpha blending. It is applied only on the
image
IMAGE_WIDTH, IMAGE_HEIGHT, IMAGE_VOFF and
IMAGE_HOFF inside the Active Video Area. Blanking
values are not clipped.
The EVO_CLIP MMIO register stores four 8-bit fields
used to clip output components. The Y output compo-
nent is clipped between the values stored in
LOWER_CLIPY and HIGHER_CLIPY. A value less than
or equal to LOWER_CLIPY is forced to LOWER_CLIPY
and a value greater than or equal to HIGHER_CLIPY is
forced to HIGHER_CLIPY.
unit
7-14
if alpha[7] = 1 then
else
(or)
by
areas
Chroma Keying
Programmable Clipping
output[7:0] = overlay[7:0]
output[7:0] = (alpha[6:0] · overlay[7:0] + (alpha[6:0] + 1) · image[7:0]) >> 7
output[7:0] = (alpha[6:0] · (overlay[7:0] – image[7:0]) >> 7) + image[7:0]
clearing
(Field 1
the
PRODUCT SPECIFICATION
and
HBE
Field 2)
bit
then
defined
reading
by
The same behavior is implemented for U and V with the
values
HIGHER_CLIPUV fields.
This mode allows fully-compliant 16 to 235 Y clipping
and 16 to 240 Cb and Cr clipping to be programmed.
These are the default values of the EVO_CLIP register
after reset.
If CLIPPING_ENABLE = 0, the EVO clips Y, U and V be-
tween the default values 16 and 240, as it is implement-
ed in the TM1000. When LOWER_CLIP{Y,UV} registers
are set to ‘0’ and HIGHER_CLIP{Y,UV} registers are set
to ‘255’, no clipping is performed.
7.16
The MMIO registers are in two groups:
• VO registers — control basic VO functions (those
• EVO registers — control new EVO unit functions
VO MMIO registers are shown in
register names are prefixed with “VO_”. Generally, their
functionality is unchanged except where noted in the text
(see for instance,
described in
are discussed in sections
EVO MMIO registers are shown in
MMIO register names are prefixed with “EVO_”. The
EVO_CTL register selectively enables new TM1300
functions. Other EVO-related registers support new
TM1300 functions. The register fields are described in
Table 7-8
sections
To ensure compatibility with future devices, any unde-
fined MMIO bits should be ignored when read, and writ-
ten as ‘0’s.
7.16.1
The VO_STATUS register is a read-only register that
shows the current status of the EVO. Its fields are shown
in
VO_STATUS[4] is now hard-wired to ‘1’. This allows soft-
ware to determine if the unit is an EVO unit (containing
extra MMIO registers) or a TM1000 VO unit, as follows.
In the TM1000, this bit is a copy of the HBE flag
(VO_STATUS[5]). In the EVO unit, it is hard-wired to ‘1’.
Software can use this bit to determine the type of (E)VO
VO_STATUS[4]. If the bit remains ‘1’, the unit is an EVO.
Figure 7-29
shared with the TM1000 VO unit)
(those new to TM1100/TM1300)
MMIO REGISTERS
7.16.4
stored
VO Status Register (VO_STATUS)
and
Table
and
and 7.16.5.
Table
Section
Table
in
7-5,
7-9. They are discussed in
Table 7-6
the
7-5.
7.16.1
7.16.1). The register fields are
Philips Semiconductors
LOWER_CLIPUV
through 7.16.3.2.
Figure
and
Figure
Table
7-29. VO MMIO
7-31. EVO
7-7. They
and