Instruction manual

Video formats, modes and bandwidth
MARLIN Technical Manua
l
Page 75
10.7 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 transferring (isochronously)
image data. Per cycle up to 4096 bytes (or around 1000 quadlets = 4 bytes) 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, there is more data to be transmitted.
The following tables indicate the volume of data in various formats and modes to be sent within
one cycle (125µs) at 400 Mb/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.
Format Mode Resolution 60
fps
30
fps
15
fps
7.5
fps
3.75
fps
0
160 x 120 YUV (4:4:4)
24 bit/pixel
1/2H
80p
60q
1/4H
40p
30q
1/8H
20p
15q
1
320 x 240 YUV (4:2:2)
16 bit/pixel
1H
320p
160q
1/2H
160p
80q
1/4H
80p
40q
1/8H
40p
20q
2
640 x 480 YUV (4:1:1)
12 bit/pixel
2H
1280p
480q
1H
640p
240q
1/2H
320p
120q
1/4H
160p
60q
3
640 x 480 YUV (4:2:2)
16 bit/pixel
2H
1280p
640q
1H
640p
320q
1/2H
320p
160q
1/4H
160p
80q
4
640 x 480 RGB
24 bit/pixel
2H
1280p
960q
1H
640p
480q
1/2H
320p
240q
1/4H
160p
120q
5
640 x 480 (MONO8)
8 bit/pixel
4H
2560p
640q
2H
1280p
320q
1H
640p
160q
1/2H
320p
80q
1/4H
160p
40q
6
640 x 480 Y (MONO16)
16 Bit/pixel
2H
1280p
640q
1H
640p
320q
1/2H
320p
160q
1/4H
160p
80q
0
7
640 x 480 Y (MONO16)
Reserved
Table 39: Format_0
As an example, VGA MONO8 @ 60 fps requires four lines (640 x 4 = 2560 pixels/byte) to transmit
every 125 µs: this is a consequence of the sensor’s line time of about 30 µs, so that no data
needs to be stored temporarily. It takes 120 cycles (120 x 125 µs = 15 ms) to transmit one
frame, which arrives every 16.6 ms from the camera. Again no data need to be stored
temporarily.
Thus around 64 % of the available bandwidth is used.