Author Topic: 50ms vs 25ms output rate  (Read 4686 times)

Offline Jeffl

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50ms vs 25ms output rate
« on: January 02, 2013, »
I have been reading more about DMX than I think I really need to know but I have a question when it comes to xLights that I still don't understand.  From what I have read, xLights outputs DMX data at 50ms which is 1/2 the standard DMX rate which I think is between 23ms and 25ms.

If you are outputting DMX data, why not output it closer to a standard rate?

Offline smeighan

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Re: 50ms vs 25ms output rate
« Reply #1 on: January 02, 2013, »
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I have been reading more about DMX than I think I really need to know but I have a question when it comes to xLights that I still don't understand.  From what I have read, xLights outputs DMX data at 50ms which is 1/2 the standard DMX rate which I think is between 23ms and 25ms.

If you are outputting DMX data, why not output it closer to a standard rate?

I can give one answer, the size of the files created for RGB devices are huge.

If I use 100ms timing (10 frames per second), i get 350 mytes for LOR lms, 1.1 gbyte for LSP UserPatterns.xml for Wizards in Winter

If i drop down to 25ms these files will be 4 times larger.

I can see maybe going to 50 ms to make smoother fades, but i am happy with my display at 100ms.

I have 12,100 channels or 24 universes. If you have 25ms that would be 484,000 updates per second.  or 116 million updates in a 4 minute song.

at my 100ms timing, i "just" have 29 million updates per song.

I like that i can load my 29 million cells in under 5 seconds on Vixen 2.1

try creating an excel spreadsheet with 12,100 rows and 9600 columns. 9600 = 4 minute song * 40 frames per second.

next year i will be closer to 16,000 channels. I think Vixen is the fastest sequencer i have tried for opening the Nutcracker created sequences.

thanks
Sean
Littleton, CO
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Offline rm357

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50ms vs 25ms output rate
« Reply #2 on: January 02, 2013, »
If my memory serves correctly, the wireless DMX that we have has problems keeping up with the 23 ms timing and the recommendation was made to back off to 50 ms. While it can be argued that you will have more accurate synchronization with the higher speed, the realities of sound propagation and the way our brain processes things, the better accuracy serves little purpose other than increasing the amount of time spent sequencing and the amount of data being pushed out. Your brain actually expects the sound to be a little late and will register it as being in sync...  A few folks can tell the difference, but most would never know.

When we step up to the pixel protocols, the theoretical max is closer to 33 ms (~30 Hz like over the air tv)
I think RJ made the decision that everything using the etherdongle would run at 50ms (20 Hz). This also makes it a lot easier to implement the conductor software - not that it is simple by any means...



Robert
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Offline Jeffl

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Re: 50ms vs 25ms output rate
« Reply #3 on: January 02, 2013, »
I can understand this for large pixels setups where you maybe can't tell if something isn't just right.  For some though that still have a regular display and want the spot on control with butter smooth fades, 100ms could be awful.  50ms seams ok.  25ms seams like heaven for DMX.

It seams like it would be nice if this could be configured somehow in xLights.

Offline dowdybrown

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Re: 50ms vs 25ms output rate
« Reply #4 on: January 03, 2013, »
I have thought about this several times. However, in the interest of keeping things simple, I am not inclined to make the timing configurable.

Matt

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Offline Dennis Cherry

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Re: 50ms vs 25ms output rate
« Reply #5 on: January 03, 2013, »
IMHO, if you use 23, 25, 50 or 100ms timing , it makes no difference to DMX, what makes a difference is you must keep all the events synced to that timing. The variable timing option should not be allowed for DMX.

If converting a sequence from one program to another and using DMX, variable timing events have to be converted to synced timing. That means the conversion software might have to make a decision on some events to turn them ON or OFF a few millisecond from the variable time.

Not everyone uses thousands of RGB channels, and file size is not the problem for some, but using non synced events is a problem.

It took me 3 seasons to figure this out in my display.

LOR's protocol is fine for LOR equipment, it only sends commands when needed, that is a non-synced protocol for their devices. I know LOR is trying to convert the output to synced DMX, but something is still not right.

All the equipment in my display appears to accept the faster data, almost all is Lynx equipment, The  4 CCR Circles seem to like the 25ms timing also, my wife even says they look so much smoother doing the SuperStar programming.

Knowing the equipment limitations of each piece of your display will help you decide what maximum timing should be used. If using wireless and the wireless only can handle maximum 50ms then do not try to send data faster than that to that portion of the display.

Remember a chain is only as strong as its weakest link.
« Last Edit: January 03, 2013, by Dennis Cherry »
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Offline Jeffl

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Re: 50ms vs 25ms output rate
« Reply #6 on: January 03, 2013, »
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I have thought about this several times. However, in the interest of keeping things simple, I am not inclined to make the timing configurable.

Matt

I wasn't thinking about just any timing configuration.  I was just thinking about the ability to a maybe configure it to 25, 50 and 100.  I think this would cover everyone.

Offline caretaker

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Re: 50ms vs 25ms output rate
« Reply #7 on: January 03, 2013, »
The 23ms rate that was in the initial post is the rate it takes a full 512 packet to send at 44HZ  So yes if you have a small display and with lets say 120 channels or less you could set it at 25ms timing and be OK but if you have a lot of RGB channels say several thousand trying to send out 8 universes of packets at 25ms would be asking for trouble, 50ms would be reasonable, 100ms safe.  The other part of the equation is what Dennis brought up and that is equipment. The one thing LOR did from the beginning was to create equipment that did the processing of effects in the hardware so when we we originally using a true serial dongle it was easy for it to send out 200 channels of data because if you wanted say twinkle the software just sent a simple command to the controller which handled the the actual twinkle effect. With DMX the twinkle effect has to be generated by to software and sent out to the DMX device taking up a lot more room in a packet.   
Jeff Squires
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Offline Jeffl

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Re: 50ms vs 25ms output rate
« Reply #8 on: January 03, 2013, »
I think with some optimization techniques all of these are solvable problems and would still be able to output at 25ms.  As far as hardware, I could see this being a problem for some LOR dongles but I think most anything else up to par.

Offline rm357

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50ms vs 25ms output rate
« Reply #9 on: January 03, 2013, »
Well, I don't think there is anything stopping you except that you may not be able to use key pieces of the lynx architecture.

Wireless - no
Active hub - no
Conductor - no

USB dongle with DMX firmware - I don't know, maybe...
EtD with dmx firmware - I don't know, but I'm thinking not
EtD with pixelnet firmware - no - active hub needed to convert pix to DMX
USB dongle with pixelnet firmware - no

LE, mr16, ssr4, Freestyle, these should all work fine.
LSP, vixen - should work, but again I don't know.
Xlights -  I think that was a no in a previous post.
Robert
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Offline Dennis Cherry

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Re: 50ms vs 25ms output rate
« Reply #10 on: January 04, 2013, »
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Well, I don't think there is anything stopping you except that you may not be able to use key pieces of the lynx architecture.

Wireless - no
Active hub - no
Conductor - no

USB dongle with DMX firmware - I don't know, maybe...
EtD with dmx firmware - I don't know, but I'm thinking not
EtD with pixelnet firmware - no - active hub needed to convert pix to DMX
USB dongle with pixelnet firmware - no

LE, mr16, ssr4, Freestyle, these should all work fine.
LSP, vixen - should work, but again I don't know.
Xlights -  I think that was a no in a previous post.

That is why testing is so important. If it say DMX then is should conform to DMX, if not then it should state the differences.

From your list you need to change the NO for the Etherdongle with DMX to YES. That is what I am using and so is Jeffl.

Have not tested other devices especially pixelnet but would say most can handle the 25ms PFS just fine, what they do with the data after that might be different. I do have the USB Dongle with DMX and will try that, I have no pixelnet equipment.

It took me three seasons to finally get my sequences with the supporting software and hardware to find the problem hardware and software issues.
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Offline Jeffl

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Re: 50ms vs 25ms output rate
« Reply #11 on: January 04, 2013, »
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Well, I don't think there is anything stopping you except that you may not be able to use key pieces of the lynx architecture.

I’m not asking for the timing to be changed to be fixed at 25ms, but rather have the option to convert and use this timing.  No hardware would be eliminated from such a change.  In fact more would be supported. 

I'm just asking for the "option".  It would be recommended to leave the "default" at 50ms.

Offline Dennis Cherry

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Re: 50ms vs 25ms output rate
« Reply #12 on: January 04, 2013, »
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Well, I don't think there is anything stopping you except that you may not be able to use key pieces of the lynx architecture.

I’m not asking for the timing to be changed to be fixed at 25ms, but rather have the option to convert and use this timing.  No hardware would be eliminated from such a change.  In fact more would be supported. 

I'm just asking for the "option".  It would be recommended to leave the "default" at 50ms.

I agree with Jeff, software should be setup for the different timings needed not change the DMX timing. the DMX specifications says max. 44FPS or 23 milliseconds for each packet, at 40 FPS you have 25 millisecond packet which is allowed. Now your E1.31 output is probably going to be either 23 or 25ms packets no matter what your sequence timing is, so if you only need 50ms timings in your software then for every 50ms event in your display it will be sent in two consecutive 25ms packets, thats the only difference, if 100ms then 4 consecutive packets will have the event.

If you have events out of the 25ms window it will not be sent, this is one of the issues the software does not address correctly using DMX. This will change now. You cannot expect a syncronized timed data stream to be able to send non syncronized events, they are just lost.

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Offline rdebolt

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Re: 50ms vs 25ms output rate
« Reply #13 on: January 04, 2013, »
I am not trying to  disagree with any of this (I find it very educational), but as far as Xlights I think that we are missing...

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I have thought about this several times. However, in the interest of keeping things simple, I am not inclined to make the timing configurable.

Matt

Sent from my LG-LS840 using Tapatalk 2



Just my $.0000001 Worth.

Keep talking thought I am learning a lot!  :)

Offline Dennis Cherry

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Re: 50ms vs 25ms output rate
« Reply #14 on: January 04, 2013, »
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I am not trying to  disagree with any of this (I find it very educational), but as far as Xlights I think that we are missing...

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I have thought about this several times. However, in the interest of keeping things simple, I am not inclined to make the timing configurable.

Matt

Sent from my LG-LS840 using Tapatalk 2



Just my $.0000001 Worth.

Keep talking thought I am learning a lot!  :)

I am glad this is educational. That is the purpose of these threads. I am trying not to think I am bashing any stuff we are using, just doing the comparisions and too inform the users.

XLights is a great program and the future looks bright with what Matt is doing. His comment is noted as not wanting to do any timing checks, and that is the way it should be. XLights conversion is taking what you sequenced and the timing and just converting that to Xseg format.
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