PRELIMINARY SPECIFICATION
14-1
Image Coprocessor
Chapter 14
14.1
IMAGE COPROCESSOR OVERVIEW
In this document, the generic PNX1300 name refers
to the PNX1300 Series, or the PNX1300/01/02/11
products.
The Image Coprocessor (ICP) connects to the PNX1300
on-chip data highway to perform SDRAM block read and
write actions. It also connects to the PCI interface to al-
low block write transactions across PCI.
The major functions of the ICP are:
Filter an image by reading the image from SDRAM
and writing the image back to SDRAM, while apply-
ing a user-defined polyphase filter with optional hori-
zontal up- or down-scaling.
Filter an image by reading the image from SDRAM
and writing the image back to SDRAM, while apply-
ing a user defined polyphase filter with optional verti-
cal up- or down-scaling.
Filter an image and convert it from planar to RGB or
YUV composite by reading the image from SDRAM
and writing the image out to PCI bus memory (graph-
ics card) or SDRAM, while performing horizontal
scaling and conversion to one of a several RGB or
YUV formats. The programmer can add optional bit-
map masking to selectively enable/disable pixel
writes to PCI (to refresh only the exposed part of a
video window) and an optional image overlay with
alpha blending and optional chroma keying (PCI out-
put only).
Move an image by reading the image from SDRAM
and writing it back to SDRAM.
All of the ICP functions move and transform data from
memory to memory or memory to the PCI bus. Hence,
the DSPCPU can use the ICP in a time-sharing fashion
to simultaneously achieve:
1. Vertical and horizontal resizing/subsampling on the
image stream from the Video In (VI) unit.
2. Vertical and horizontal resizing/upsampling on the im-
age stream sent to the Video Out (VO) unit.
3. Presentation of a collection of live video windows with
programmable up and down scaling and arbitrary
overlap configuration on PCI graphics cards.
1
Full 2D scaling and filtering requires two passes over the
data: one for horizontal scaling and filtering and one for
vertical scaling and filtering.
Figure 14-1
shows a block diagram of the PNX1300 with
the ICP.
Figure 14-2
shows a block diagram of the inter-
nal structure of the ICP. The ICP contains a 5-tap filter,
YUV to RGB converter, an overlay and alpha blending
unit, and an output formatter. These blocks communicate
with each other through FIFOs that also buffer the block
data to and from the PNX1300 Data Highway. The ICP
uses a microprogram-controlled sequencer to control its
internal timing. The program for this sequencer is in a ta-
ble in SDRAM. The ICP reads the appropriate portion
from the SDRAM each time the ICP is commanded to
perform a function. Microprogram control simplifies and
minimizes the ICP hardware and increases the flexibility
of the ICP to perform additional tasks without adding
hardware.
14.2
REQUIREMENTS
14.2.1
Functions
The major functions of the ICP include:
1. Read an image from SDRAM and write the image
back to SDRAM, while applying a user defined
polyphase filter with optional up or down scaling in
horizontal direction.
2. Read an image from SDRAM and write the image
back to SDRAM, while applying a user defined
polyphase filter with optional up or down scaling in
vertical direction.
3. Read an image from SDRAM and write the image out
to PCI bus memory (graphics card) or SDRAM, while
performing horizontal scaling and conversion to one
of a several RGB and YUV formats. The PCI output
mode includes optional bitmap masking to selectively
enable/disable pixel writes to PCI (to refresh only the
exposed part of a video window) and optional RGB
overlay with alpha blending and optional chroma key-
ing.
14.2.2
Bandwidth
ICP bandwidth can be estimated from the worst-case im-
age processing bandwidth. If the worst case image is
1024 x 768 at 30 Hz in YUV 4:2:2 format, the pixel rate is
1024 x 768 x 30 = 23.59 Mpix/sec. For YUV 4:2:2 image
coding at 2 bytes per pixel, this is 23.59 x 2 = 47.19 MB/
1.
Note that function 2 and 3 don
’
t normally occur simulta-
neously, and if an application attempts both simulta-
neously, some performance limitations are incurred.