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Keeping two videos in sync?



  • Anyone have a good tip for keeping two long videos in sync? 

    I have two movie files that start at the same time, but slowly drift out of sync over time. Testing the setup with a 3:30min movie the difference is just a few milliseconds. However the end result is two tightly synced movies that are 3 hours long and run all day long in an installation lasting weeks. My client has been testing the longer versions and notices the off sync at 11 minutes in...and that is before the videos loop. 

    Both movies are 1080p, HAP codec, and run off a MacBook Pro 15" Early 2013 2.7 GHz Core i7. 


    Surely this community has some good solutions. Thanks for helping out a noob...


  • Tech Staff

    @three5eric

    You could try my "syncvideo" user actor: https://community.troikatronix...

    Best Michel



  • if they are both playing on the same computer, render them into a large double wide movie and user chopper or the mapper to show the half you want. Gauranteed not to drift at all.



  • Fred's solutions is the best way to do it, all in sync frame by frame.



  • @michel - this is a nice little User actor, thanks. is it more accurate than running the position of 2 movies using the same envelope? i'm designing an installation that has to sync up projectors over 2 floors of a building, so will need to use 2 computers networked together with a Net Broadcaster/Listener system. I was thinking of using an Envelope Generator on one machine running the position of a Movie Player on that machine and also on a Movie Player upstairs. the Movs will be about 20 minutes and will loop for 3 days. I was thinking of adding a Calculator into the system to compensate for any delay that might be visible. Any advice is appreciated...

    cheers, John



  • @dbini I would adjust the speed of the movies as little as possible and position even less, so if you are using an envelope generator plugged into the position of a movie player you might not get the best results. Just altering the speed if the position is different (as Michels actor does) is a much better approach.


  • Tech Staff

    @dbini

    Best is to use the actor on the slave machine but add the math (network delay) on the master machine before its sent to the slave. Make sure you use a codec where every frame is present (ProRes, HAP...), you can also export a h264 file and set to "every frame is a keyframe", the file size will be higher than normal but it would work fine changing speed values. And make sure you have a wired connection from computer to computer.

    @mark wrote in another post:

    I just did a simple test, sending from one computer to another and back and a wired LAN. The round trip time for both Net Broadcaster and OSC was 1 mS (0.001 S). They were totally equivalent.

    Best Michel



  • Great solutions. Thanks all..!