How does bandwidth affect the frame rate?
PIKE Technical Manual
V5.0.0
270
How does bandwidth affect the frame
rate?
In some modes the IEEE 1394b bus limits the attainable frame rate. Accord-
ing to the 1394b specification on isochronous transfer, the largest data pay-
load 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 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 121: 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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