Appendix B - Troubleshooting - Black Box iPATH ACR1000A-CTL-24 User Manual

APPENDIX B - TROUBLESHOOTING

PROBLEM: THE VIDEO IMAGE OF THE AGILITY REMOTE SHOWS HORIZONTAL LINES ACROSS THE SCREEN.
This issue is known as Blinding because the resulting video image looks as though you're viewing it through a venetian blind.
When video is transmitted by Agility units, the various lines of each screen are divided up and transmitted as separate data packets.
If the reception of those packets is disturbed, then blinding is caused. The lines are displayed in place of the missing video data
packets.
There are several possible causes for the loss of data packets:
• Incorrect switch configuration. The problem could be caused by multicast flooding, which causes unnecessary network traffic.
This is what IGMP snooping is designed to combat, however, there can be numerous causes of the flooding.
• Speed/memory bandwidth issues within one or more switches. The speed and capabilities of different switch models varies
greatly. If a switch cannot maintain pace with the quantity of data being sent through it, then it will inevitably start dropping
packets.
• One or more Agility units may be outputting Jumbo frames due to the video resolution (2048 horizontal pixels) being used. If
jumbo frames are output by a Agility unit, but the network switches have not been configured to use jumbo frames, the switches
will attempt to break the large packets down into standard packets. This process introduces a certain latency and could be a
cause for dropped packets.
• One or more Agility units may be using an old firmware version. Firmware versions prior to v2.1 exhibited an issue with the timing
of IGMP join and leave commands that caused multicast flooding in certain configurations.
REMEDIES:
• Ensure that IGMP snooping is enabled on all switches within the subnet.
• Where each Agility unit is connected as the sole device on a port connection to a switch, enable IGMP Fast-Leave (aka Immediate
Leave) to reduce unnecessary processing on each switch.
• Check the video resolution(s) being fed into the Agility locals. If resolutions using 2048 horizontal pixels are unavoidable then
ensure that Jumbo frames are enabled on all switches.
• Check the forwarding mode on the switches. If Store and forward is being used, try selecting Cut-through as this mode causes
reduced latency on lesser switch designs.
• Ensure that one device within the subnet is correctly configured as an IGMP Querier, usually a layer 3 switch or multicast router.
• Ensure that the firmware in every Agility unit is version 3.3 or greater.
• Try adjusting the local settings on each Agility to make the output data stream as efficient as possible.
PROBLEM: THE AUDIO OUTPUT OF THE AGILITY REMOTE SOUNDS LIKE A SCRATCHED RECORD.
This issue is called Audio crackle and is a symptom of the same problem that produces blinding (see previous page). The issue is
related to missing data packets.
REMEDIES:
As per blinding discussed above.
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