Sync 32 Projectors on 4 Machines

[xergon]

Heyho,

I need to make a small installation in two months from now, I need to control 32 XGA Projectors which are placed in 4 different places. They all project on the same surface, so the projectors will all be (partially) stacked and Edge-Blended.

Now I wonder if this can be done with Resolume.
Controlling 8 Projectors with one Computer works like a breeze, now I wonder how to Sync them more or less frame accurate.

I already tried to sync 2 computers via the osx master/slave system, it did work allright via wifi, but this ain´t optimal when expanding up to 4 or more computers as each Computer would need to process the data for all 32 projectors.

So I need to frame-sync Resolume with another method. Any recommendations?

Using DMX to trigger the clips on each computer simultaneously won´t work cause after 7 or 8 minutes the clips won´t by in sync anymore but 3-5 frames apart. With everything stacked and edge-blended this might look ugly.

Any help is appreciated! Did i forget any methods? How is SMTPE Sync meant to work?

Best,
Stefan

[Joris]

Syncing via an external protocol like OSC or SMPTE are your best options.

SMPTE is basically a fancy way to control the playhead of a video via an external audio signal. It does nothing to sync the resulting output from the computer. So if you are sending the playhead via OSC, you are basically doing the same thing as when using SMPTE.

Keep in mind that even when sycning the playhead of each computer, you might not get frame accurate sync. Each computer is running its own processes, so it may be slightly quicker or slower in decoding the sync signal, fetching the pixel data from disk, or rendering and outputting the final result. Especially when edge blending two computers together, or when seamlessly stitching them together in a single LED wall, there can be a noticeable difference between frames.

this ain´t optimal when expanding up to 4 or more computers as each Computer would need to process the data for all 32 projectors.

I don't quite follow. If you split up the content into four different videos, each computer would only need to process the data for 8 projectors. This brings down the load considerably, as processing the pixel data is the bottleneck. Sending the required OSC data for clip triggers and the playhead is only a few kb. When you use a wired network, this has practically zero impact on the processing.

[Oaktown]

When you use a wired network, this has practically zero impact on the processing.

I would recommend using a dedicated 1G wired network and OSC syntax to sync all four computers from an external controller and make sure you set your IP addresses manually.

I need to control 32 XGA Projectors which are placed in 4 different places. They all project on the same surface, so the projectors will all be (partially) stacked and Edge-Blended.

Why do you need to separate into 4 computers? 32 XGA projectors is only two 4096x3072 so assuming you can drive the composition, you could run everything off one computer and two 4096x3072 DP outputs by daisy chaining 4 Datapath fX4 units off each output.

[Zoltán]

SMPTE is an audio signal, which has a hours:minutes:seconds:frames time data encoded in it,
If you listen to it, it sounds like noise, but you can play it from any audio player, even resolume.
Then you need to split that audio signal and feed it to the line inputs of your computers, set up the input, and the clip offsets to the correct timecode. Launch the clips, play the SMPTE and the playhead will jump to the SMPTE time+offset.
You can generate timecode wav files here http://elteesee.pehrhovey.net/.
There are also hardware based SMPTE generators, and I think Qlab can generate SMPTE too.
You also need to trigger the clips in sync, Resolume can't do that via SMPTE natively.

Do you need to play audio too?

(Joris mentioning the processes of the individual computers... a while ago I think we talked about the video engine getting its sync from the sound card.
If that's the case, you can sync two sound cards together with Wordclock, usually high end sound cards have these feature, with a BNC connector, or you can sync the cards via S/Pdif or optical ADAT etc.
So anyway that may help to get the engines in sync.)

[xergon]

Hey,
thanks guys for your help! You are awesome!

@ Joris:
I only managed to sync playheads when I use exactly identical compositions on each computer, so each computer was processing the same master video file with all data inside. The master computer is sending osx sync data via unicast (.255) to all machines in the network.
I imagine resolume is just checking for filenames and not for file data when running laptops in a master-slave configuration. is this correct? So I could use the same filenames = same compositions, but with different projection data inside.
Or is there a more elegant way to just sync the playheads and trigger the clips/column?

@Oaktown:
you are thinking of this one here? http://palffyzoltan.hu/?url=controller
Yep, wired is much better than wifi for sure, even with parabol antennas we had some packet loss and thus stuttering in the osc synced playhead... any way to prevent this? *asking for a new feature here*

Regarding the DP / Datapath topic, you are right, this would be an elegant method. I`ll go for this if the syncing will not work. It´s just that I don´t have 8 fx4, and the projectors will be placed in 4 or even 5 different towers, each around 50m apart from each other. It´s maybe more easy to run one Ethernet Cable to each tower and connect the projectors directly to the different Servers, instead of running 64 hdmi-ethernet converters and cables with lengths ofup to 150m. Also, we might have to upgrade to 36 or 40 projectors. Always good to stay flexible

@ravensc:
thx for the SMPTE Introduction! Indeed, it´s way more convenient to trigger clips via network, so OSC might be the better solution. Good tips with the Wordclock synchronization. I like this!

[Zoltán]

Hey,
I imagine resolume is just checking for filenames and not for file data when running laptops in a master-slave configuration. is this correct? So I could use the same filenames = same compositions, but with different projection data inside.
Or is there a more elegant way to just sync the playheads and trigger the clips/column?

you don't even need the file names to be identical, just the clip length.

@Oaktown:
you are thinking of this one here? http://palffyzoltan.hu/?url=controller
Yep, wired is much better than wifi for sure, even with parabol antennas we had some packet loss and thus stuttering in the osc synced playhead... any way to prevent this? *asking for a new feature here*

The stuttering is my experience too with osc, but I think it's not frame loss, but network lag. The playhead position arriving/processed at the slave late with a playing clip, thus the playhead jumps back to the osc position.
The Controller you mention, in the relay mode synces up master resolume to slaves but by default filters the playhead position with audio clips to get rid of the stuttering. (This can be overriden of course.)
Any osc capable program would work to trigger the columns Controller, Qlab, or even from a mobile phone, TouchOsc for example.
In Qlab you need to set up every cue manually, with Controller you just open the resolume composition and your layer 1 clipnames are there as cues instantly to trigger the columns.

With SMPTE you can fine tune the playhead position.
What I would do is trigger the columns in sync via an external osc source, together with an SMPTE signal and have the clips synced to that, with multiple machines.

If you can go for one machine and the datapath way that will work too.
You can place the datapaths at the projectors, they can work standalone once they are set up.Much less cabling than the synced machine method.

[xergon]

Thanks for your answer!
I wonder about the frame stuttering ... starting the clips in a synced way ain´t a problem in my view, but keeping the clips in sync is the difficult part.
Syncing via SMTPE is causing less stuttering than OSC in your experience? I would imagine that than this might be a bug in Resolume? Or is the Audio-In faster than the Ethernetport, lag-wise? Interesting

I like your idea about the datapath splitters being directly in the projection towers, but how to transfer the Displayport-Signal via 50-70 Meter?

[francoe]

how to transfer the Displayport-Signal via 50-70 Meter?

That's the easy part, just need money and buy some dp extenders.

[Oaktown]

You could also use HDMI over HDBaseT which would be a lot cheaper. The only limitation would be to use 30Hz rather than 60Hz but you can convert back to 60Hz in the Datapath fX4.

[Joris]

(Joris mentioning the processes of the individual computers... a while ago I think we talked about the video engine getting its sync from the sound card.
If that's the case, you can sync two sound cards together with Wordclock, usually high end sound cards have these feature, with a BNC connector, or you can sync the cards via S/Pdif or optical ADAT etc.
So anyway that may help to get the engines in sync.)

To be completely clear, only Resolume's internal timing comes from the audio card. Things like the BPM, Beat Snap, timeline automation, Autopilot timing, that all comes from a clock that's using the audio card. When you're using an external protocol to sync playheads, you bypass all this internal timing completely.

Inaccurate framesync or horizontal tearing is caused by two video cards not refreshing at the same time. SMPTE or Wordclock are not going to do anything for you in this.