First get the timescale of the movie you're working with (gettimescale message). Say your movie has a QT timescale of 600. That means that 600 QT time values == 1000 msecs. So 1200 QT time values would be 2 seconds, 1800 QT values would be 3 seconds, etc.
enable that output and use that in place of the groove~ output.
sfplay's is millisec position, so you have to divide by 1000.0 and multiply by the timescale (usually 600), to get get the proper quicktime "time" (not "frame") attribute value based on millisecond time.