Pike Technical Manual
V5.2.0
281
How does bandwidth affect the frame rate?
How does bandwidth affect the frame
rate?
In some modes the IEEE 1394b bus limits the attainable frame rate. According to
the 1394b specification on isochronous transfer, the largest data payload size of
8192 bytes per 125 μs cycle is possible with bandwidth of 800 Mbit/s. In addi-
tion, there is a limitation, only a maximum number of 65535 (2
16
-1) packets per
frame are allowed.
The following formula establishes the relationship between the required
Byte_Per_Packet size and certain variables for the image. It is valid only for For-
mat_7.
If the value for
BYTE_PER_PACKET
is greater than 8192 (the maximum data pay-
load), the sought-after frame rate cannot be attained. The attainable frame rate
can be calculated using this formula:
(Provision:
BYTE_PER_PACKET
is divisible by 4):
ByteDepth based on the following values:
Formula 20: Byte_per_Packet calculation (only Format_7)
Formula 21: Maximum frame rate calculation
Mode
bit/pixel
byte per pixel
Mono8, Raw8
8
1
Mono16, Raw16
16
2
YUV4:2:2
16
2
YUV4:1:1
12
1.5
RGB8
24
3
Table 131: ByteDepth
BYTE_PER_PACKET
frame rate[1/s]
AOI_WIDTH
AOI_HEIGHT
ByteDepth [byte]
125 [μs]
=
frame rate
BYTE_PER_PACKET [byte]
AOI_WIDTH
AOI_HEIGHT
ByteDepth [byte]
125 [μs]
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