Instruction manual
Marlin Technical ManualV.2.7.0
123
Video formats, modes and bandwidth
Frame rates
An IEEE 1394 camera requires bandwidth to transport images.
The IEEE 1394a bus has very large bandwidth of at least 32 Mbyte/s for transfer-
ring (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 cam-
era requires a certain percentage of maximum available bandwidth. Clearly the
bigger the image and the higher the frame rate, there is more data to be trans-
mitted.
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:
They enable you to calculate the required bandwidth and to ascertain the num-
ber of cameras that can be operated independently on a bus and in which mode.
Note
To configure this feature in an advanced register see Table 116:
Advanced register: Autofunction AOI on page 214.
Note
All bandwidth data is calculated with:
1 MByte = 1024 kByte
Format Resolution Max. video format
Format_0 up to VGA 640 x 480
Format_1 up to XGA 1024 x 768
Format_2 up to UXGA 1600 x 1200
Table 50: Overview fixed formats