Converting 60 FPS TIME to 30 FPS TIME

Posted by mhnfcpx 
Converting 60 FPS TIME to 30 FPS TIME
July 19, 2016 12:16AM
I have a video edited in FCPX that is 1920 X 1080I at 59.54 FPS.

It has been suggested to me to use the "Create Blue Ray" device in Compressor to produce a ".264" file to use in a Blue ray authoring program, authored Blue Ray disk.

I have done this in the past many times and it produces a good HD disk viewable on standard HD TV's.

The problem is that Compressor produces the file at 30 FPS. So if I have a marker set in FCPX at say where I need a chapter marker, I can't enter this value, it is invalid. So how do I find that same spot when viewing the timeline in 30 FPS video that is the Same spot in FCPX when the play head is at ??

Is there a conversion formula for this???

Re: Converting 60 FPS TIME to 30 FPS TIME
July 20, 2016 06:24PM
You've posted in the FCP7 forum and you'll get an FCP7 answer.

Your details are too unclear for you to get your "conversion formula".

Firstly, 60 fps isn't 59.94 fps.

Also a 1080I video -- properly 1080i -- is interlaced, and isn't 60 fps or 59.94 fps. The "f" in "fps" means frames, not fields.

Also denotes a rather unusual timecode. Check your punctuation! "Dropframe" timecode is sometimes written with those four periods, though FCP7 writes it with three colons and a semicolon. If you have dropframe timecode then it means 1 hour + 9 minutes + 54 seconds + 58 frames. The mention of 58 frames implies that your framerate is greater than 58, so either 59.94 or 60. Dropframe would only make sense with 59.94 fps, and FCP7 does allow you to choose dropframe with 59.94 fps. Thus dropframe timecode is good for measuring display time.

If the timecode is written 1:09:54:58, with four colons, it is non-dropframe. Then if the video is 60 fps the timecode means 1 hour + 9 minutes + 54 seconds + 58 frames, but if the video is 59.94 fps the same timecode does not mean 1 hour + 9 minutes + 54 seconds + 58 frames. Horribility! The non-dropframe timecode is counted as if the video is playing at 60 fps though it's really playing at 59.94 fps. So the 1 hour is really 60*60*60 = 216000 frames which makes 1.001 hour of play at 59.94 fps. Etc. Non-dropframe timecode is good for counting frames.

You say you've converted 59.94 fps video to 30 fps. Really? If so there are two quite different conversions you might have made. One way throws away every other frame from the 59.94 fps video. The resultant is declared 30 fps, but then it plays with 0.1% faster action than when it was 59.94 fps. The other is to replace every 59.94 frames with 30 frames, as nearly as possible. Almost every other frame is thrown away, except every so often the converter abstains. The resultant plays back at 30 fps with the original speed of action.

If you're trying to compare the time codes of the 59.94 fps video to the 30 fps video you have to know the kind of timecode you used with the 59.94 fps video and also the kind of conversion you made.

If you dislike all these details you can try replacing 1|09|54|58 with 1|09|54|29 -- ignore punctuation; divide the frames number by 2 -- and crossing your fingers. Otherwise, the details.

Dennis Couzin
Berlin, Germany
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