File: vin.fm5, modified 7/24/99
PRELIMINARY INFORMATION
6-1
Video In
Chapter 6
by Gert Slavenburg
6.1
SUMMARY OF FUNCTIONS
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 (54 MB/sec) raw input data channel.
Direct 8-10 bit interface for video A/D converters at
up to 54-MHz sample rate.
Receiver port for TM1100-to-TM1100 unidirectional
message passing
The Video In unit operates in one of the modes as per
Digital video input is in YUV 4:2:2 with eight-bit resolution
multiplexed in CCIR656 format1 from a digital camera or
CCIR656 capable video decoder (such as the Philips
SAA7111 or SAA7113), across an eight-bit-wide inter-
face. 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 for-
mat to TM1100 SDRAM. The video camera or decoder
can be programmed using the TM1100 I2C 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 is performed by software on the
DSPCPU or by the on-chip Image Coprocessor (ICP).
When operating as raw input data channel, VI accepts
eight-bit-wide data. The operation mode is
raw8 capture.
No data selection or data interpretation is done. Data is
written 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 ac-
cepted at the clock of the sender. If desired, VI_CLK can
be programmed as an output to drive the data transfer at
a programmable rate.
VI can accept data from up to 10-bit A/D converters, at
sampling rates up to 54 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 Video Out unit of another
TM1100. One Video Out can broadcast to multiple re-
ceiving VI’s. In this
message passing mode, no data se-
lection 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 cur-
rent memory buffer is full. If the memory buffer fills before
message end is encountered, the received data is trun-
cated and an error condition is raised.
6.1.1
Interface
Besides the Video-In-specific pins in
Table 6-2, the
TM1100 I2C interface is typically used to control the ex-
ternal camera or video decoder.
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. Video In Mode Selection.
Mode
Function
Explanation
0000
fullres capture
YUV 4:2:2 capture without dec-
imation
0001
halfres capture
YUV 4:2:2 capture with deci-
mate by 2
0010
raw8 capture
raw 8 bits data capture, pack 4
bytes to a word
0011
raw10s capture
raw 10 bits data capture, sign
extend to 16 bits, pack 2 to a
word
0100
raw10u capture
raw 10 bits data capture, zero-
extend to 16 bits, pack 2 to a
word
0101
message passing
VO to VI message passing
0110
..
1111
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.