Video Frame/Audio Sample Conversion

[bytz]

I'm having problems mapping NTSC frames to a time/drawing location. Currently the sofware is using the integer approximation 30000/1001 in it's calculations, this however will often cause the rendered time of the video clip to be 1 frame off from the audio rendering i.e. as in a timeline using rectangle to show when and how long the clips are.

I tried converting the integer math to floating point and then used a ceiling funtion to convert the factional frame to a frame, which works ok for most situations except at some point the the approximation produces an extra frame.

I'd think that this is a fairly well documented occurance but I haven't found anything that would help.