PRELIMINARY SPECIFICATION
6-1
Video In
Chapter 6
by Gert Slavenburg
6.1
VIDEO IN OVERVIEW
n this document, the generic PNX1300 name refers
to the PNX1300 Series, or the PNX1300/01/02/11
products.
The Video In (VI) unit provides the following functions:
Digital video input from a digital camera or analog
camera (using a video decoder).
High-bandwidth (81 MB/sec) raw input data channel.
Direct 8-10 bit interface for video A/D converters at
up to 81-MHz sample rate.
Receiver port for PNX1300-to-PNX1300 unidirec-
tional message passing
The VI unit operates in one of the modes per
Table 6-1
.
Digital video input is in YUV 4:2:2 with 8-bit resolution
multiplexed in CCIR656 format
from a digital camera or
CCIR656-capable video decoder (such as the Philips
SAA7111 or SAA7113), across an 8-bit-wide interface.
Resolutions up to CCIR601 are accepted at 50 or 60
fields per second. A programmable rectangular image is
captured from a video frame and written in
planar format
to PNX1300 SDRAM. The video camera or decoder can
be programmed using the PNX1300 I
C bus. In
fullres
capture
mode, luminance (Y) and chrominance (U, V)
pass unmodified. In
halfres capture
mode, luminance
and chrominance are horizontally decimated by a factor
of two to convert to CIF-like resolution with YUV 4:2:2 or
MPEG sampling rules. If vertical subsampling on chromi-
nance is desired, it can be performed by software on the
DSPCPU or by the on-chip image coprocessor (ICP).
When operating as raw input data channel, VI accepts 8-
bit-wide data. The operation mode is
raw8 capture.
No
data selection or data interpretation is done. Data is writ-
ten in packed form, four bytes to a word, to local SDRAM.
There is no hardware control over the rate at which the
source sends data. Instead, VI maintains two pointer/
counter registers to ensure that no data is lost when the
local SDRAM memory buffer fills. Data is accepted at the
clock of the sender. If desired, VI_CLK can be pro-
grammed as an output to drive the data transfer at a pro-
grammable rate.
VI can accept raw data from up to 10-bit A/D converters,
at sampling rates up to 81 MHz. VI can operate in
raw8,
raw10u,
or
raw10s capture
mode for eight-bit, unsigned
10-bit or signed 10-bit data. In the 10-bit modes, data is
zero- or sign-extended to 16 bits and stored in packed
form in local SDRAM. As with the
raw8-capture
mode, VI
maintains two pointer/counter registers to ensure that no
data is lost when the local SDRAM memory buffer fills.
Data is accepted at the externally set sampling rate. If
desired, VI_CLK can be programmed as an output to
serve as a programmable sampling clock.
VI can act as receiver from the Enhanced Video Out
(EVO) unit of another PNX1300. One EVO unit can
broadcast to multiple receiving VIs. In this
message
passing
mode, no data selection or data interpretation is
done. Each message of the sender is written as byte-
packed data to a separate local SDRAM memory buffer.
Message start and end is indicated by the sender. The
receiving VI will accept data until the sender indicates
message end or until the current memory buffer is full. If
the memory buffer fills before message end is encoun-
tered, the received data is truncated and an error condi-
tion is raised.
6.1.1
Interface
Besides the VI-specific pins in
Table 6-2
, the PNX1300
I
C interface is typically used to control the external cam-
era or video decoder.
Figure 6-1
through
Figure 6-4
illustrate typical connec-
tions for commonly used external sources. Note that
VI_DVALID is only used in special circumstances, e.g.
when sending data through a channel that results in
clock periods both with and without data transfers.
Table 6-1. VI unit mode selection.
Mode
Function
Explanation
0000
0001
0010
fullres capture
halfres capture
raw8 capture
YUV 4:2:2 capture, no decimation
YUV 4:2:2 capture, decimate by 2
raw 8-bit data capture, pack 4
bytes to a word
raw 10-bit data capture, sign
extend to 16 bits, pack 2 to a word
raw 10-bit data capture, zero-
extend to 16 bits, pack 2 to a word
0011
raw10s capture
0100
raw10u capture
0101
0110
..
1111
message passing message reception from EVO
Reserved
1.
Refer to CCIR recommendation 656: interfaces for dig-
ital component video signals in 525-line and 625-line
television systems. Recommendation 656 is included in
the Philips Desktop Video Data Handbook.