Machine Vision

 

Our recently released pylon version contains several new features. A streaming statistics feature for the GigE Vision connection is one of them. This direct feedback offers a quantification of the connection quality and helps to improve the setup.

The GigE Vision interface for machine vision benefits from the advantages of now-common Gigabit Ethernet network technology, such as long cable lengths of up to 100 meters and a wide variety of available accessories including hubs and switches. In addition, the GigE Vision interface uses the UDP data protocol. UDP defines, for example, how IP addresses must work and how the data stream from the camera to the connected PC must be organized. Images captured by a GigE camera must be packed into data packets before transmission to the host PC can be started. Because the UDP protocol is designed as an "open connection", the loss of some data packets is accepted and expected. There are various reasons for this data loss, beginning with low cable connection quality and ranging to very high bandwidth loads or a limited size of the incoming buffer used on the PC's GigE network adapter. When the Basler pylon driver is used with a Basler GigE camera, the "resend" mechanism incorporated the camera can compensate for any lost packets. Missing packets are simply requested a second time from the camera's internal memory. The vision application will always get complete images without any additional actions.

Resending, however, consumes additional bandwidth and CPU load. The Basler pylon driver offers several parameters that can be used to minimize the resend behavior for all kinds of hardware setups.

These parameters include, for example, the size of the packages or the "start transmission delay". Now, pylon's new streaming statistics provide additional clear feedback about the connection's qualities. At runtime, the driver will count, for example, the total number data packets transferred and the number of packet resend requests. It then offers this information to the application via new elements included in the pylon API. The pylon viewer continuously monitors the statistics and displays them in the viewer's "Features" window under the "Statistics" parameter in the "Stream Parameters" group. The user can now simply find the best setup for each connection by trial and error.

The Statistics feature is available for pylon’s GigE Vision Filter driver, which is hardware independent, and for pylon’s GigE Vision Performance driver, which works with Intel cards.

>>Download the pylon 2.1 release now!

Tested and proven

A test in the Basler lab demonstrated the performance of the new GigE Vision streaming statistics feature. On a Dell Precision M6400 laptop equipped with 32 bit Vista, three piA640-210gc pilot cameras transferred captured images into the PC memory at full speed. Each camera was connected to the laptop via a different NIC:

NIC 1: NetGear PCMCIA GA511, PacketSize 3000
NIC 2: OnBoard GA511, PacketSize 1500
NIC 3: DeLock Express Card /34 (PCI-Express for Notebooks), PacketSize 3000

All cameras were capturing images at VGA resolution in 8-bit BayerGB8 mode with a speed of 210 fps each. The screen shot of the pylon viewer shows that with the initial setup, there were some resend requests that could all be accommodated. A reduction of the packet size for the PCI-Express card from 8000 to 3000 bytes addressed this situation and no further resends were requested!

For more information, please contact us at +49 4102 463-515 or e-mail us at bc.support.europe@baslerweb.com.