SAA7201H Philips Semiconductors, SAA7201H Datasheet - Page 18

• Manufacturer Part Number: SAA7201H
• Description: Integrated MPEG2 AVG decoder
• Manufacturer: Philips Semiconductors

Philips Semiconductors
C
Additionally to the above defined graphics boxes one
cursor can be activated on the screen. Since the cursor
data is fully stored locally, no overlapping restriction apply
to this box so the cursor can moved over the entire screen.
The cursor can be as large as 1 kpixel with a 2 bits/pixel
colour depth. Obviously data transfer can be done on DMA
basis and need only be performed when a cursor is
required or when its contents must be modified.
The cursor XY dimensions (where the Y dimension refers
to frame lines) can be selected between 8
32
zoom with a factor 2 can be applied in both directions
independently.
The cursor pixels will be translated via a 4-entry CLUT to
YUV colours and a transparency factor T. The resolution
of the YUV parameters is 6, 4, 4 bits respectively.
The T parameter is coded in 2 bits to enable the mixing
with video and graphics in 4 steps being 100% (cursor
only), 50%, 25% and 0% (fully transparent cursor).
Display unit
Before feeding the MPEG decoded and graphical data to
the output, a display unit re-formats the MPEG specific
4 : 2 : 0 format to CCIR-601 4 : 2 : 2 format and performs
a mixing between video and graphics where required.
The output picture can be up to 720
or 720
A schematic representation of this unit is shown in Fig.11.
1997 Jan 29
handbook, full pagewidth
URSOR PROCESSING
In a first step a selected window can be retrieved from
the decoded MPEG data. This might be useful for e.g.
pan and scan operations for aspect ratio conversion.
Integrated MPEG2 AVG decoder
32, 64
480 pixels at 60 Hz.
16 and 128
decoded
MPEG
picture
8. On top of these shapes, a
EXTRACTION
UP-CONVERSION
WINDOW
CHROMA
576 pixels at 50 Hz
128, 16
SCALING
Fig.11 Display unit.
GRAPHICS
64 STEP
64,
MIXER
18
SHIFTING
In case the resulting number of pixels per line does not
match the 720 pixels/line output format a horizontal
scaler can be activated. This scaling unit can transform
any number of bits below 720 to the required output
format. Internally a poly-phase filter is used which
performs a 64 phases interpolation. Not only
up-conversion but also down-conversion is supported
up to a scaling by a factor 2. Thus horizontal scaling can
be performed in a range from 0.5 up to 64. In practice
the maximum up-conversion factor will be less or equal
to 4.
In vertical direction the picture can be expanded or
scaled down, in both cases by a factor 2. Expansion with
a factor 2 might be relevant for the up-conversion of SIF
resolution pictures to full screen. The factor 2 scaling, if
combined with the appropriate horizontal scaling, results
is
graphics. This might be very useful for electronic
program guide applications. It should be noted that in
case of picture compression an anti-aliasing filter can be
activated.
Shifting: when the resulting MPEG picture is smaller
than the 720
be located anywhere on the display screen.
Moreover, the non-covered area can be given any
background colour.
Clipping: the amplitude of the MPEG decoded and
re-scaled video signal is kept within the range 16 to 235
for luminance and 16 to 240 for both chrominance
components.
1
CURSOR
4 STEP
4
MIXER
picture thus freeing-up a large screen area for
CLIPPING
MGD331
576 (480) display format, this picture can
FORMAT
OUTPUT
to digital
CVBS
encoder
Objective specification
SAA7201