Dropouts on Ravenna Network

[jkurtz11]

I was hoping to get some advice from other Horus/Hapi and Pyramix Native/Core Audio users out there. We are having some trouble with audio dropouts occurring on our Ravenna network. The network runs throughout our music building at the university which makes many of the ethernet cable runs quite long, possibly 300+ feet long. And the cable type may be cat5, not cat6, but I'm not sure. I may have to check into that if that could be part of the problem.

Our setup consists of one Horus, and one Hapi, and two dell switches. We'll have our Horus in a Hall which is connected to our main Dell switch. In our control room, we have a second Dell switch which is connected to the main Dell switch. The reason for this is because we only have one ethernet run from our control room to the main switch and we need to connect our computer as well as our hapi, and sometimes a backup computer as well. I have made sure to load the proper setup files downloaded from Merging for each switch, and it is a completely closed network, meaning it is not connected to the university's network - ie... no internet access. Also, following a recommendation from our dealer, I changed the default ip address of the 2nd switch to be 169.254.252.2, so that it would not conflict with the other one which is 169.254.252.1 . So we have two switches connected together to create the network.

I'm fairly certain that it is not a clocking problem. All our devices are locked and the nature of the dropouts do not seem like typical clock problems. I don't know if it is significant, but the dropouts using the core audio driver and Pro Tools are always exactly the same length, about 30ms. And it happens with Pyramix as well, although the dropouts there were only 22ms. They seem to occur randomly, sometimes after 2-3 minutes of recording, sometimes after 5 minutes. Sometimes there are a couple within a minute or two of each other, and sometimes they are 5 minutes or more apart, so there doesn't seem to be any sort of predicable pattern, aside from the fact that they are all exactly the same length. These are clearly audible and visible as flat lines in the waveform.

As it occurs in both core audio and Pyramix. I have tried just about every combination of buffer sizes, both on the Horus/Hapi latency setting, the core audio control panel, and pro tools hardware buffer. After talking to our dealer I have now turned them up to the highest setting on the Hapi and Horus, and the core audio panel.

I have some more troubleshooting to do by trying this out in different rooms, but I do know that we do not have any problems when we are using the rig remotely, and only using one switch and cable runs of 100 ft. This leads me to believe that it is either 1) the fact that we have two switches tied together or 2) the fact that the ethernet runs in our music building are either too long or the cable is not a high enough grade.

This is occurring at 44.1kHz, with only 2 channels. Would that indicate that it is not a bandwidth/cabling problem? It occurs on multiple computers. We've tested it with our Mac Pro Quad Core, as well as a new Macbook Pro.

Does anything come to mind for anyone? Is there a document somewhere that describes the cable requirements and limits for Ravenna? As I am not a networking expert, is there anyway to easily test our current cable setup to determine if it is either too long a run or not a high enough grade? Any suggestions would be welcome.

Thanks,

Justin Kurtz

The Hartt School

[Silas]

Hi Justin,

I wish I had some real help for you but I don't. However, I suggest you contact David Jaques at Merging directly ASAP. He's brilliant with this stuff.

Best Wishes,
Silas

[a-w-a]

Many, many, many years ago (if not more ) I was the System Architect for a major telecommunications company and so for my sins I was forced to familiarise myself with such matters even if only to politely pass the time of day at seminars and conferences with others of my ilk*. The maximum certified length of a single continuous run of cable for both cat5 and cat6 is 90m. If your runs of cabling also pass through electronically noisy areas with high amounts of electromagnetic interference then their effective length will also be reduced so it may be best to reroute cabling if this is the case.

Without further ado I must be off to find a use for Pythagoras' theorem, I amy be gone quite a while...

All the very best - Andrew

* Any similarities between aforementioned telecommunications conferences and the Black Eyed Peas video for "I gotta feeling' are both coincidental and wishful.

[Julian Gough]

Does anything come to mind for anyone? Is there a document somewhere that describes the cable requirements and limits for Ravenna? As I am not a networking expert, is there anyway to easily test our current cable setup to determine if it is either too long a run or not a high enough grade? Any suggestions would be welcome.

I understand that the recommended upper limit is 100m using CAT5e or better.

Using better cable or converting to fibre will enable longer lengths.

For location work I use a 100m drum of screened CAT5e with a 10m link between the drum and the switch, a total length of approx 360 ft.

Since you don't have a problem when on location, it does point to the infrastructure you are using. Perhaps the switches are not set up correctly or there is a badly made RJ45 connector somewhere. Quality of cable over that length could be an issue or a combination of everything resulting in a perfect storm of data errors.

I did consider there might be something else on the network that is hogging bandwidth, but if you are only using 2 channels of audio, that probably isn't the problem.

Sounds like you will have to go back to the old fashioned way of fault finding and change one thing at a time in order to narrow down the problem.

Good Luck.

Julian

[jkurtz11]

Update - We have determined that the problem only occurs in a couple of our rooms that are quite far from the switch, and also have old, likely cat5 cable. I am going to try and test to find out the length of the run and also the grade of cable to confirm that this is the problem. Additionally we will be double checking the wiring integrity to make sure there is not a bad termination our some sort of passive coupler or extender somewhere. It's sort of a relief to be narrowing in on the problem, even if it means re-running the cable with cat 5e or cat6.

Justin

[crna59]

Just some anecdotal information. I can't get our Horus to work at all with CAT5. Using CAT5e or higher, it works perfectly

[FelipousisMix]

Hi: actually it doesn't matter if it's CAT5 or CAT6, 100 meters is still the max for any network cable on copper.