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Thread: Skipping Genlock & Disabling Frame buffers

  1. #1
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    Skipping Genlock & Disabling Frame buffers

    Back in the days before genlock you would bring your next camera up on preview and then cut/transition to it to allow the switcher to align the cameras. These days most switchers have frame syncs to make sure each input's frames are starting at the same time for clean cuts at the expense of adding 1 frame of latency to the pipeline etc.

    I am looking to use fiber for some long distance runs when we do IMAG with the TC-1. Currently when we do IMAGI use Genlock with my Canon XF-305s and disable the frame syncs and we are able to do a projection that lines up close enough to audio to pass inspection. If the frame syncs are on the delay is large enough that people see the gap between video and audio and someone moving has a visible delay.

    I am now being asked to do setups that require longer and longer camera runs that are beyond SDI and turn me to fiber and the solutions I have seen don't allow for genlock analog signals etc.

    So, any issue with disabling the frame syncs and just making sure I don't hot cut on the program row? I plan to do some testing but wanted to ask here as well.

    Thanks!

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    Good luck.

    You can have a look on Bluebell stuff which we sold quite a lot. They can make SDI one way and genlock opposite way, also with RS422 and/or ethernet control if needed ( PTZ stuff or RCp commands), with only one duplex ( even sometimes simplex ! ) singlemode fibre.

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    Thank you I will take a look at that. In my testing of recording on the TC1 and recording via SDI onto a black magic mini recorder I was getting clean cuts between my two cameras with frame sync disabled, I was not however able to output to another screen to test latency before/after to make sure it was behaving as expected. Will do some more testing to be sure.

  4. #4
    'the write stuff' SBowie's Avatar
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    Depending on your setup, you can usually test latency by doing a loopback from TC output to another input.
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    Quote Originally Posted by SBowie View Post
    Depending on your setup, you can usually test latency by doing a loopback from TC output to another input.
    Yeah I will probably do something similar to that. Just wanted to setup a laptop or something playing back video with timecode on it and take a picture of all of them in one go to look from the frame drift present.

  6. #6
    'the write stuff' SBowie's Avatar
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    Sure, just bear in mind that external devices will often add to the latency burden. The loopback will tell you exactly what TriCaster own real contribution to the total is.
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    yeah the way I did this in the past was:

    Camera HD-SDI out > SDI DA -
    | -> Blackmagic Duo 2 Input 1
    |-> Tricaster TC1 input 1 -> Mix 1 SDI out . -> Blackmagic Duo 2 Input 2

    This told me the latency of the Camera, DA, Monitor and then Tricaster's Interface Screen, and then eventually SDI out the same monitor at the end. It seemed about as good as I could figure with this stuff...
    Last edited by stp_productions; 06-19-2019 at 03:12 PM.

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    'the write stuff' SBowie's Avatar
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    A simple loopback of a countdown clip in a DDR isolates TriCaster's end-to-end latency - using Program out as source to one of its own SDI inputs, through the Switcher and back to, say, Preview. With the countdown on Program, and the post-capture, post-switcher Input appears Preview, and the difference says it all. This eliminates latency of the camera (which can be considerable), converters, etc. I generally use a 60P session for this, to make the display easier to read.
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    I thought about doing that but I also wanted to make sure anything happening from the SDI input also occured in this test. My cameras are 60i unfortunately so I stick with that do my tests reflect what I will use on a show.

  10. #10
    'the write stuff' SBowie's Avatar
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    Quote Originally Posted by stp_productions View Post
    ... from the SDI input also occured in this test.
    Sending program to an SDI input takes that into account, right?
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    I guess so. I was thinking more of the devices in use sdi monitor/projector vs the DVI/HDMI but I guess that is besides the point.

    So if I am reading this correctly we are 3 frames behind when the frame buffer is on and about 1.5 when off.

    I am still curious if my understanding of taking cameras to the preview row before cutting to them should deal with the clean cut issue like it would on a traditional switcher or if I still risk tearing/partial frame switching in the setup where I turn frame syncs off. I cant see an issue but limited testing and would love feedback if anyone has any.
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