I was wondering what you are using to calculate your Timecode SOM/Duration with milliseconds. From my understanding there are 33.3 milliseconds per frame. But then I used that value to convert your milliseconds to frames, then convert that to NTSC Drop Frame my SOM/Durations are not matching MediaInfo's data. I am using a Apple App "time:calc" to convert Frames to Timecode in 29.97 frame rate.