Image Transmission Over Gigabit Ethernet; Smartek Gige Vision Filter Driver; Udp Packet Resend Mechanism - Smartek Vision Giganetix GC Series User Manual

5 Image Transmission over Gigabit Ethernet

The network interface of SMARTEK Vision digital cameras is designed to be fully compatible with the GigE
Vision standard. The following section describes features of the data interface of the Giganetix series as
well as the SMARTEK Vision GigEVision Filter Driver. Further, several optimization settings of the network
driver are introduced and the pixel structure of the image data is elaborated.

5.1 Smartek GigE Vision Filter Driver

Ethernet packets can come from various sources and do not have to be in order. This makes it necessary
that each data segment is usually routed through the whole network stack of the operating system until it is
delivered to the target application. The CPU load can especially at high data rates be significantly affected
by this process as well as the latency of the image stream. The UDP protocol, used for the transmission
with low latencies, is furthermore not able by default to handle packet loss - packet collisions lead inevitably
to a loss of image data.
To optimize the data transmission and add features like an optimized packet resend mechanism, SMARTEK
Vision provides its own GigE Vision filter driver. The filter driver separates streaming video packets from
the rest of network data already before the network stack of the operating system gets access to them and
forwards them directly to the application. It is designed to be compatible with the most network adapter
cards and significantly lowers the CPU load needed to service the network traffic between the PC and the
camera(s).

5.1.1 UDP Packet Resend Mechanism

The Packet Resend mechanism is a driver feature that, when enabled, tries to regain packets that have
been lost during transmission. It checks the order of the incoming packets and detects if one or even a
group of packets is missing in a stream. Depending on the parameters settings the driver will then send one
or several resend requests to the camera which resends the appropriate packets. Table 62 shows the basic
driver parameters available.
Parameter
SetParametersToDefault
MaxImageSize
EnablePacketResend
AcceptIncompleteImage
LineFormat
Table 63 lists further parameters, allowing a detailed configuration of the Packet Resent mechanism. All this
parameters mainly affect the performance and the robustness of the packet resending, changes should only
be done carefully.
Type
CMD
Integer
Boolean
Boolean
Enumeration
Table 62: Packet Resend Parameters (1/2)
127
5 Image Transmission over Gigabit Ethernet
Description
Resets all parameters of the Packet Resend
mechanism to the default values
Maximum image size that the Packet Resend
mechanism will handle
Enables / Disables the Packet Resend
mechanism
Enables / Disables the acceptance of images
where payload packets are missing
Internal (electrical) circuit of the line
SMARTEK Vision Giganetix User Manual Version 2.1.4