Sequencing Timing

When faced with choosing a refresh rate within Xlights or any other sequencing software, there are currently three choices 10, 20 and 40 frames per second. Which one should you choose?

If you look at computer monitors refresh rates must get above 60-80 hertz before people do not notice the scan rate. If you look at videos, a mismatch of video to sound of -95mS to +25mS is not noticeable for most people. You could use this for choosing your display rate, but it depends upon what you are using for your show.

If you are mostly using the software to drive motion and have a few AC strings or dumb RGB LED strings the 10 hertz rate would be sufficient and would make sequencing easier.

If you are driving mostly AC strings and dumb RGB LED’s to music and want to be precise on timing the 20 hertz refresh rate is a very good choice. In fact this is basically the default used by most people.

However, if you are using a lot of the built in sequences in Xlights to drive smart RGB LED’s you might want to consider a different refresh rate. The beat in most songs is 100-120 beats per minute or about two beats a second. I have about 100 lights across the front of my house. If I want to use a curtain effect the lights are broken up into the following segments for each refresh rate.

10 Hertz, 5 samples in 1/2 second – 20 lights lit per sample
20 Hertz, 10 samples in 1/2 second – 10 lights lit per sample
40 Hertz, 20 samples in 1/2 second – 5 lights lit per sample

Looking at the numbers above, if you want smooth effects for your light show you should choose the maximum refresh rate of 40 hertz. For me this is the best choice and since my show is not very large, it really no problem for the hardware or software.

If you look at the high end software like Madrix, they have the option to drive the LED’s off the DVI/HDMI port. This is probably where things will go in the future. Note that ACN 1.31 only supports refresh rates to 42 hertz.

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