sACN over Wifi

[mark_s]

Does anyone have any experience of sending sACN (or Artnet, or other protocol of choice) over Wifi in a theatre environment? I'm contemplating using a wireless link between the FOH control position and stage on an upcoming project, and was wondering if anyone had any real-world experience of the reliability of using Wifi for the link. I don't want negative replies along the lines of 'DON'T DO IT' from people who haven't tried it - I'm well aware of the consequences of failure and have weighed up the pros and cons in my head already - I just want some feedback from real-world experience to tell me whether I should bother even trying it out.

 

My current idea is to have the FOH control kit go into an access point, and to locate a wireless bridge and switch on-stage in the wings, with cable between this and all of the fixtures. I'm not suggesting a wireless link between FOH and every bar/device, but a point-to-point type link between FOH and stage, with everything else being cabled.

[Joe Bleasdale]

There have been multiple shows, even a good few large ones, using wireless DMX with good success. Whether you mean using consumer based products to send the data or not I don't know, but obviously that isn't really advisable. I'd speak with someone like Luminex or ELC and see if they have any professional level products that you can use.

 

One thing that has come up in the past, as a backup, if you can run the cable then do that. Even if you do use the wireless just make sure you still have that cable option.

 

Thanks.

[mark_s]

Yes, I mean rather than using a specifically-designed wireless DMX product, I want to send sACN (or IP-based protocol of choice) wirelessly using some off-the-shelf 802.11 products. I'm more curious about whether anyone has had any success in the real world doing it than anything else - I'm toying with the idea of trying it out, but I'm not seriously considering it for any important projects in the near future!

[cameroncoats]

One thing that has caused problems for me in the past: some consumer routers/access points only like non-routable local IP's (afaik 172.16.*, 192.168.*, 10.0.*). Some go one step further, and don't like anything other than 192.168.*.*

[timmeh2]

Hi

 

Yes I do it, with wireless MANet so I can program from sitting in the auditorium and for using a PDA on the stage for helping with focussing.

 

I also stream ArtNet for use with a wireless lighting product.

 

The first pitfall is that not all wireless routers support it - you need to get one that both supports NAT and port forwarding. You'll need to set rules for your AP otherwise your devices won't see the traffic.

 

Over a 54mb G connection, a single stream running at full speed can overwhelm a P2P link even with 100% signal quality. 108/N-rated links can improve reliability a bit, but you still won't get anywhere near 100mbps connection speed. The access point will generate a bottleneck in your network as the packets arrive and leave it - for this reason it's best to have a solid ethernet backbone with the access point on its own link. Dumb switches are OK, but with a managed switch you will be able to slow down the speed to the router should it start to drop packets. Don't even attempt to use a hub - it will just cause you problems.

 

By the far biggest issue with streaming this kind of network data is that there is no provision for signalling packet loss in the end device. It has no idea if it has missed anything. One missed frame could mean the difference between a blackout working or not. Most desks are quite clever in the way they spit out their data, for instance my MA only sends data if a stream's values are changing, but also sends the last frame a number of times to guarantee that it got received by all. It will also send a status packet every 3 seconds so that the devices know that the stream is still alive (which is the ArtNet standard)

 

How much data you send down your network will have a direct affect on what % success rate you get. I can quite easily get 100% over 54G with one universe with a low refresh rate - for example I can control a media server wirelessly and it will work pretty much perfectly, as the rate at which the DMX is sent to it isn't huge. On the other side I also experimented with sending the video data the same way, with a stream rate of 40fps. The result was a lot of dropout and missed frames, even with a line-of-sight 54mbs connection.

 

Its not really about how many universes you have. If you have 10 but each is only generating one frame per second then you'll have better results that a single one doing 40fps.

 

So, to answer your question, yes can be done, however you will need to spend a while playing with your router and optimise it. Out-of-the-box settings for APs are all about reliability rather than speed, and things like channel auto-hop and down-negotiation of link speeds will hamper your efforts.

 

HTH

 

All the best

Timmeh

[grandMA_the_2nd]

The MA remote does not stream MA Net via Wifi, it is purely an emulator from the console to the PDA or iPhone/iPad. MA net requires minimum 100mbps and MA Net2 requires a gigabit connection..

 

There used to be a wifi based DMX system that I think was made by Avo, used to work fine until the audience arrived, then 1000+ mobile phones in the crowd would upset it greatly...

[Joe Bleasdale]

As already mentioned, with consumer level kit IP addresses can usually be a problem. If your using Art-Net say bye bye to 2.x.x.x addresses. Also, even in the medium price range the routers offered just don't offer the configurability required. Hell, I have seen high end ones that don't do basic things like port forwarding. One thing I saw come up recently in another discussion was that (especially with Art-Net) alot of routers don't let you turn off Broadcast Storm Control, also known as Traffic-Storm Control. When there becomes too much of this type of packet, a layer 3 device, ie Router or switch will simply destroy them.

 

I think the higher end routers and devices are the ones to clamp an eyeball on. Cisco and HP seem to be popular in the entertainment industry. I can tell you with some certainty, pulling your BT Home Hub out of the house to put into your network won't help ;)

 

Thanks.

[Don Allen]

I got caught out using a budget wirelss DMX link in a hotel atrium, luckily to just two Exterior 600's. The link worked fine for several hours in the morning, then something kicked in in the afternoon and the link failed. So something may seen ok one day and fails the next with lower end gear.

[Ken Coker]

http://www.bbc.co.uk/cbbc/clips/p00ktyz5 - seems pretty off the shelf to me....

UDP packets I believe.

No idea what the IPad software was - if you have a look at L&SI and ETNow there are more details as I recall.

 

KC

[timsabre]

http://www.bbc.co.uk.../clips/p00ktyz5 - seems pretty off the shelf to me....

UDP packets I believe.

No idea what the IPad software was - if you have a look at L&SI and ETNow there are more details as I recall.

 

KC

 

I don't think that wifi link from the ipad is actually sending the DMX/Artnet though, which is what the original question was about. The wifi system pictured in the clip is some sort of remote control to a console, which requires much less data.

[abbotsmike]

From an entirely network perspective, look at getting a wifi AP/router that you can install dd-wrt firmware on. It allows you to control pretty much everything mentioned here, including upping transmit power on some devices.

[mark_s]

Some interesting points raised here that I'd never have considered (such as mobile phone interference with an audience) - thanks guys.

 

From an entirely network perspective, look at getting a wifi AP/router that you can install dd-wrt firmware on. It allows you to control pretty much everything mentioned here, including upping transmit power on some devices.

 

That was my exact plan - a pair of cheap APs which support DD-WRT. The thought was inspired by the fact that I have a Linksys WAP54G lying on my desk doing absolutely nothing, and I was wondering whether I could put it to good use somehow.

 

As already mentioned, with consumer level kit IP addresses can usually be a problem. If your using Art-Net say bye bye to 2.x.x.x addresses. Also, even in the medium price range the routers offered just don't offer the configurability required. Hell, I have seen high end ones that don't do basic things like port forwarding. One thing I saw come up recently in another discussion was that (especially with Art-Net) alot of routers don't let you turn off Broadcast Storm Control, also known as Traffic-Storm Control. When there becomes too much of this type of packet, a layer 3 device, ie Router or switch will simply destroy them.

 

Thanks.

 

Addressing shouldn't be a problem - using the 2.0.0.0/8 subnet is irrelevant as the network shouldn't be connected to anything public anyway, and if for some odd reason it really is a problem as Artnet also supports 10.0.0.0/8 in later versions. Not that I would use Artnet anyway - from a computing point of view, I think it's incredibly ugly. Port forwarding is also irrelevant as all of the devices will be on the same network - there's no NAT or routing going on.

 

On a pedantic note, the vast majority of switches are layer 2 devices.

[Modge]

Not that I would use Artnet anyway - from a computing point of view, I think it's incredibly ugly

It gets less so with each revision - broadcast need only be for discovery now for one thing (since version 2).

[Sully]

Some interesting points raised here that I'd never have considered (such as mobile phone interference with an audience) - thanks guys.

 

From an entirely network perspective, look at getting a wifi AP/router that you can install dd-wrt firmware on. It allows you to control pretty much everything mentioned here, including upping transmit power on some devices.

 

That was my exact plan - a pair of cheap APs which support DD-WRT. The thought was inspired by the fact that I have a Linksys WAP54G lying on my desk doing absolutely nothing, and I was wondering whether I could put it to good use somehow.

 

...

 

Addressing shouldn't be a problem - using the 2.0.0.0/8 subnet is irrelevant as the network shouldn't be connected to anything public anyway, and if for some odd reason it really is a problem as Artnet also supports 10.0.0.0/8 in later versions. Not that I would use Artnet anyway - from a computing point of view, I think it's incredibly ugly. Port forwarding is also irrelevant as all of the devices will be on the same network - there's no NAT or routing going on.

 

On a pedantic note, the vast majority of switches are layer 2 devices.

 

Off the shelf APs like that could do the job but leaves you at the risk of interference on 2.4GHz as these tend to have omnidirectional antennas and the 2.4Ghz can be a bit noisy in some areas. If it were me I'd get a pair of something like:

 

http://www.wifigear.co.uk/ubiquiti-nanostation-m5-loco

 

Which are a bit more directional, higher bandwidth which should give ample headroom, 5.8Ghz (Which has a much lower chance of interference issues) and come with the passive PoE injectors allowing remote powering.

For outdoor use you need a light touch 50 ukp a year license from Ofcom but for indoor point to point use you just have to keep the power below a certain level and use certain parts of the 5.8Ghz band.

 

David.

[Ken Coker]

I don't think that wifi link from the ipad is actually sending the DMX/Artnet though, which is what the original question was about. The wifi system pictured in the clip is some sort of remote control to a console, which requires much less data.

 

This doesn't answer the OP, but it does add to the font of human knowledge. Jon Milmer has written to me thus:

 

The BT tower job was surprisingly simple actually, we were using my iPad running the MA lighting remote running the MA2 desk. The desk was at the base of the tower. We were using the MA-Net with nodes positioned where the lights were. We ran Ethernet from the base of the tower up through the core to the 27 th floor into a switch so we could position the node there then continued up to 41 which is the top of the tower. Total Ethernet run was 150m from desk to top of tower. The switch on 27 was at 100m so we could boost the signal.

 

The iPad was connected to the network through a little wireless access point which in turn was connected to a long distance wireless connection, which is a high power microwave link (line of sight from the top of our building at imagination to the 8th floor of the BT Tower) which as far as the network was concerned was just another length of cat5 cable.

 

The iPad and the desk have no reason to think that they are not next to each other. So no UDP packets directly from the iPad.

 

Thanks Jon

 

KC