Guppy PRO Technical Manual
V4.1.2
180
How does bandwidth affect the frame rate?
In some modes the IEEE1394b 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
addition, 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
Format_7.
If the value for BYTE_PER_PACKET is greater than 8192 (the maximum data
payload), 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 is based on the following values:
Note
Certain cameras may offer higher packet sizes, depending on
their settings in combination with the use of FirePackage.
Consult your local dealer's support team, if you require
additional information on this feature.
Formula 18: Byte_per_Packet calculation (only Format_7)
Formula 19: Maximum frame rate calculation
Mode
bit/pixel
byte per pixel
Mono8, Raw8
8
1
Mono12, Raw12
12
1.5
Mono16, Raw16
14
2
YUV4:2:2
16
2
RGB8
24
3
Table 99: ByteDepth
BYTE_PER_PACKET
frame rate
AOI_WIDTH
AOI_HEIGHT
ByteDepth
125 μs
=
frame rate
BYTE_PER_PACKET
AOI_WIDTH
AOI_HEIGHT
ByteDepth
125 μs
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