Delay an output
  • dougatron
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    Delay an output

    by dougatron » Wed Jan 24, 2018 12:03 am

    Hey, first post! Not sure if this is the right board so please move it if needed :)

    I'm going to be using MadMapper (on Windows) in an upcoming project with 2 projectors and an LED wall. I need to play a video across all 3 displays and am concerned that the LED wall may have a slight delay compared to the projectors. Is there a way within MadMapper to delay an output by a certain number of frames? If not, can I request this feature to be added - although I realise this wouldn't happen in time, so any hints as to how I could do this via Spout for example would be greatly appreciated :)

    Many thanks

    Doug
  • mad-matt
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    Re: Delay an output

    by mad-matt » Wed Jan 24, 2018 12:15 am

    Hi Doug,
    Maybe someone will have better advice for your situation.

    First, what kind of LED screen is it ? Is it taking a DVI signal ? Did you check the latency already ?

    If there is about one frame latency, you can make a Spout loopback for each projector, so you'll have 4 projectors in MadMapper: 2 where you do the mapping and that are published to spout, and two other that are assigned to the real projectors and that will just display a Quad with the corresponding spout input. That will make one frame latency, no more.

    If you have a BlackMagic device with HDMI input you can also do a hardware loopback (it will have more than one frame delay) but that will use more resources, however since you're only using 2 projectors, on a good computer you can use more.

    If you use NDI loopback (like the spout setup described above) you'll have more latency, but it will do video compression / decompression so it depends on your hardware. 2 Full HD streams encoding + decoding you have to check.

    Maybe there are spout tool for that, no idea...

    If your video content is just a movie, you could have two versions of the same movie with a few frames delay, then start them exactly at the same time (the version for LED screen + the version for projectors) and it will stay in sync (we handle the playback with high resolution so I'm confident the two movies wouldn't drift even after a few days)

    Cheers
    Matt
  • dougatron
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    Re: Delay an output

    by dougatron » Wed Jan 24, 2018 12:55 am

    Hi Matt

    I haven't had a chance to check the latency for real yet but it's a ROE Black Onyx LED wall running through a Brompton Tessera M2 Processor (which states 3 frames of latency) from a DVI output. The projectors are Panasonic DZ13Ks running over SDI (can't find any values of latency for them however). The last option of adding the appropriate number of frames delay to the start of the video definitely sounds the best idea, and shouldn't take too long to sort out I guess (my first test of the set-up is the night before show day!)

    On the point of multiple videos staying in sync. Would you recommend software or hardware decoding for this? I was semi-considering putting all 3 clips into a single 5760 x 1080 clip for guaranteed sync, but if you don't think this is necessary I'd happily run them separately. As this is my first use of MadMapper on Windows, I'd also be interested to know your recommended video codec for the platform?

    Also, thanks for the Spout tip, that's very clever! Could well be useful for a last minute fine adjustment :)

    Cheers for your help 👍🏻

    Doug
  • dougatron
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    Re: Delay an output

    by dougatron » Wed Jan 24, 2018 12:55 am

    :lol: That's the biggest emoji ever!
  • mad-matt
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    Re: Delay an output

    by mad-matt » Wed Jan 24, 2018 12:16 pm

    I don't think it's usefull to make a big movie with the three movies. You can assign a computer keyboard key on the "play" button + the "rewind" button. Then pressing this keep will move all movies to loop start point. They will keep in sync.
    You don't even have to export different movies at a time offset. If you use one movie for each output (2 projectors + LED wall) you can simply adjust the loop start of the movie going to the LED wall screen (to 0.2 seconds if it has 0.2 seconds latency). By right clicking the "loop start" or "loop end" value, you can change edit mode to "time in seconds" or "frame number"
  • dougatron
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    Re: Delay an output

    by dougatron » Wed Jan 24, 2018 11:37 pm

    simply adjust the loop start of the movie going to the LED wall screen (to 0.2 seconds if it has 0.2 seconds latency). By right clicking the "loop start" or "loop end" value, you can change edit mode to "time in seconds" or "frame number"
    Matt this is absolutely perfect! So long as I leave Hardware Acceleration disabled, It's rock solid with the exact number of frames delay that I've entered!
    🙌🏻

    Any recommendations on my best choice of codec for Windows?

    Thanks for your help :D
  • mad-matt
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    Re: Delay an output

    by mad-matt » Mon Jan 29, 2018 11:51 am

    H264 is you just playback the movie forward

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