SAA7201H Philips Semiconductors, SAA7201H Datasheet - Page 20

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

Philips Semiconductors
JTAG
The SAA7201 supports the standard Boundary Scan test
instructions: bypass, extest, sample, intest, runbist,
idcode.
Memory requirements
As indicated before the MPEG source decoder operates
with 16 Mbit of external memory. Several processes
require access to the external memory, mostly being the
video decoding process. In normal main level, main profile
video applications about 1.2 Mbit of memory space is free
for non-video processes. In practice most of this capacity
will be used for graphics. In combination with the internal
variable length decoding, full screen graphics at 8-bit per
pixel is feasible. Moreover, by having introduced a flexible
memory allocation procedure the available memory
capacity for graphics may be enlarged when decoding
lower resolution MPEG pictures or when the input bit rate
is less than 15 Mbit/s.
Table 1 Required memory capacity for some user defined modes
1997 Jan 29
Audio input buffer
Video input buffer
Video implementation buffer (R/P)
Slave synchronization buffer (R/2P)
Reference and decoded picture
Total for video + audio
Remains for OSDG (2
Integrated MPEG2 AVG decoder
Chroma interpolation
3 : 2 pull-down
Picture format
Bit rate (R)
System
24
= 16777 kbit)
64 kbit
1835 kbit
600 kbit
300 kbit
13456 kbit 12719 kbit 9609 kbit
16255 kbit 15518 kbit 12108 kbit 15090 kbit 13292 kbit 10391 kbit
522 kbit
720
frame
n.a.
576
64 kbit
1835 kbit
600 kbit
300 kbit
1259 kbit
720
15 Mbit/s
50 Hz
field
20
n.a.
Obviously for graphics-only applications all 16 Mbit can be
used for the storage of bit-maps and look-up tables.
In Table 1 an overview is given of the required memory
capacity for some user defined modes.
In 50 Hz systems memory capacity can be saved by
restricting the chroma vertical interpolation to field
interpolation. This mode would only bring some extra
chroma resolution in case the input stream contains
progressive coded pictures.
In 60 Hz systems the reduction of storage capacity for
B-frames to field capacity has not only consequences for
the chroma vertical interpolation but also for the
3 : 2 pull-down operation mode. The operation
repeat-first-field is not possible in all cases and a modified
3 : 2 pull-down is performed under the control of the
SAA7201. The user may decide to use this modified
3 : 2 pull-down mode in order to have more memory
available for OSD or graphics.
576
64 kbit
1835 kbit
400 kbit
200 kbit
4669 kbit
544
field
n.a.
576
64 kbit
1835 kbit
500 kbit
250 kbit
12441 kbit 10634 kbit 8042 kbit
1687 kbit
full MPEG
720
frame
480
15 Mbit/s
64 kbit
1835 kbit
500 kbit
250 kbit
3485 kbit
720
modified
Objective specification
60 Hz
field
480
SAA7201
64 kbit
1835 kbit
300 kbit
150 kbit
6386 kbit
720
modified
9 Mbit/s
field
480