Hmm. It's been a while since I worked with LTC or Smpte, but if you're looking for a running visual SMPTE display FileMaker is not the tool to use. There's no way it will be fast enough. Not the right engine.
No it doesn't have to be a running visual display. When a key is pressed It just needs to record the timestamp.
A late reaction: I just read this and I don't know much about this, but we have a plug-in that can read from a (virtual) serial port. Maybe you can make it work, with an audio-in to serial conversion, and then have Troi Serial Plug-in read the data.
Our plug-in can work for example with an Arduino ( a cheap computer / electronics platform based on easy-to-use hardware and software.)
Here is our plug-in:
And here is a link to the arduino:
I hope it helps to get it solved for you.
This is an interesting problem. I'm curious, why do you need the SMPTE time code? In FileMaker there are a number of methods for getting time. My favorite for determining script/process performance is Get(CurrentTimeUTCMilliseconds).