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How does bandwidth affect the frame rate?
How does bandwidth affect the frame
rate?
=
BYTE_PER_PACKET
Formula 14: Byte_per_Packet calculation (only Format_7)
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
16
65535 (2
-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.
×
frame rate[1/s]
AOI_WIDTH
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):
BYTE_PER_PACKET [byte]
≈
------------------------------------------------------------------------------------------------------------------------------------------- -
×
AOI_WIDTH
AOI_HEIGHT
Formula 15: Maximum frame rate calculation
ByteDepth based on the following values:
Mode
bit/pixel
Mono8, Raw8
Mono16, Raw16
YUV4:2:2
YUV4:1:1
RGB8
Table 100: ByteDepth
×
×
AOI_HEIGHT
×
ByteDepth [byte]
byte per pixel
8
1
16
2
16
2
12
1.5
24
3
×
ByteDepth [byte]
125 [µs]
×
125 [µs]
PIKE Technical Manual V4.1.0
226
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