Black frames at the end of an exported file when converting from 60p to 24p

Question

I have another export issue that I can't figure out.
I import footage I shot at 23.98fps (on a JVC HD100) using a Kona LH card at 59.94fps DVCPro HD, in which it has a 2:3 cadence. I need to make files that are actually 23.98p DVCProHD. Unfortunately, when I export in Final Cut from the 59.94 original, the new 23.98 file has all of the image, exported correctly, followed by a number of black frames such that the total number of frames in the exported file equals the number of frames in the original file. That is:
If the original 59.94 file was 3s long, that is 60 * 3 = 180 frames. The exported 23.98 file also has 180 frames, but only 3s of image = 3 * 24 = 72 frames, followed by 180 - 72 = 108 frames = 4s 12frames of black.
How can I prevent this from happening, and end up with an exported file that is (e.g.) just the 3s of image, and not 7.5s of which 4.5s are black?
It's true that I can manually clip this black off, but I need to do many clips as a batch, and would really not have to change one clip at a time. It is also true that I can do a batch in compressor, and that this process does not suffer this problem -- that is, there is no extra black -- however, there is another problem: the original 59.94 DVCProHD files are actually 1280x720 with square pixels; the files exported from FCP via the KONA DVCProHD codec maintain this true HD proportion, but the ones exprted through compressor (which does not appear to support the KONA LH implementation of DVCProHD as an option) have the size 960x720 with anamorphic pixels, and I would rather keep the original size. Thus, I would rather export from fcp. If anyone has any insight into how I might resolve this....
Thanks,
Robert Schaller

Answer 1

Thanks. If I understand you correctly, it does seem to export correctly if I paste the 59.94 clip into a 23.98 sequence (you can't nest sequences that have different time bases) and export from there, and it doesn't even have to specify square pixels, etc.: the AJA codec implementation seems to take care of that. There is no longer any extra black, so, per file, that gives the right result.
That, however, is only one part of the problem, though a significant part. Next is, I really would like to do this as a batch process, as I tend to have many clips to do at one time. As soon as I try any kind of batch export, I end up with one of two problems:
1) if I try to batch export from fcp, I'm back to having extra black frames, or
2) if I try to batch export with compressor, I get 960x720 files.
If anyone has any suggestions on how to get the right files in a batch, that would be the next step. Is fcp scriptable? And, if so, can you write a script that takes a clip, pastes it into a blank 23.98 DVCPro timeline, sets the correct in and out points (i.e, in at the beginning and out 1 before the end), exports it with a specified codec and time base, with a name based on the source clip, and then repeats that as needed?
Thanks for any input --
Robert Schaller