hi, if i understand correctly, and you want to control Start AND Stop point of the Recording, you could try to use Shutter Gating Mode in Combination with some kind of External Frequency Generator, which would control the Framerate (which could even change during the Recording itself, if needed, with such a setup) and duration of the Recording, which would be Controled by your digital output.
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If however controling only the End or start of the Recording would be enough, you could get away with a much simpler setup, usually only requiring to give the Camera a single High or Low signal at a trigger input at the Time you want it to start or stop (depending on the input and Settings for it). This could be done with a single electronic switch, like an Transistor or something like this, or, if you allready have the Correct signal Level and Type of signal from your digital output, you might even be able to feed that directly into the Camera.
