Video Frame/Audio Sample Conversion

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.

You can insert the same video frame twice in places where the video lags audio. For every 299 frames you render insert a frame (299th frame twice) and make it 300.

Thanks for the suggestion, but the problem is not the play back, but in the representation of the relative start and duration times on a time line.

What makes rendering differ from representing it by a timeline? You can insert an extra while displaying it in the timeline.