Allied Guppy, Техническое руководство, Страница: 146 / 238

Video formats, modes and bandwidth
GUPPY Technical Manual V4.0.1
146
Frame rates
An IEEE 1394 camera requires bandwidth to transport images.
The IEEE 1394a bus has very large bandwidth of at least 32 MB/s for trans-
ferring (isochronously) image data. Per cycle up to 4096 bytes (or around
1000 quadlets = 4 bytes@ 400 Mbit/s) can thus be transmitted.
Depending on the video format settings and the configured frame rate, the
camera requires a certain percentage of maximum available bandwidth.
Clearly, the bigger the image and the higher the frame rate, the more data
requires transmission.
The following tables indicate the volume of data in various formats and
modes to be sent within one cycle (125 µs) at 400 Mbit/s of bandwidth.
The tables are divided into three formats; F_0 up to VGA, F_1 up to XGA, and
F_2 up to UXGA.
They enable you to calculate the required bandwidth and to ascertain the
number of cameras that can be operated independently on a bus and in which
mode.
The frame rates in video modes 0 to 2 are specified, and settings are fixed
by IIDC V1.3.
In video Format_7 frame rates are no longer fixed.
GUPPY F-025
tbd
GUPPY F-029
tbd
Note
L
• If the cameras are operated with an external trigger the
maximum trigger frequency may not exceed the highest
continuous frame rate, thus preventing frames from
being dropped or corrupted.
• IEEE 1394 adapter cards with PCILynx™ chipsets have a
limit of 4000 bytes per cycle.
Note
L
Different values apply for the different sensors.
Frame rates may be further limited by longer shutter times
and/or bandwidth limitation from the IEEE 1394 bus.