Back in the day an electron beam was running across the TV screen. NTSC was running with 30 and PAL with 25 frames a second. If the beam would go line by line the screen would flicker. The solution was, to let it run twice over the screen for each frame: Once for all odd lines (1,3,5 etc) and then again for all the even ones (2,4,6). That looked better. It is called ‘interlaced’. Each of these passes is a ‘field’.<\/p>\n
Film cameras liked to run at 24 frames per second. Cinema does not flicker since each frames is shown twice, but that is not the point here.<\/p>\n
When you have 24 fps footage and your TV runs at 30fps, what do you do? The solution was to insert a so called 3:2 pulldown to make 30 frames out of 24. This was done based on 60 fields to make it look smooth.<\/p>\n
Interlacing is dead. There are no electron beams going over glass tubes to make images to speak of.<\/p>\n
If you like to compress an NTSC spot that was shot on film, and that has the 3:2 pulldown in it, then you should go back to the 24fps version first. Since I could not find anything that worked I developed this. In 1998. Then, in 2008, I needed it again, and so I looked again. Much to my surprise, nothing really worked the way it should be. Many tools have the button to do an ‘inverse telecine’. But none detect cuts and deal with changing cadence patterns. So, I wrote it again. This time based on quicktime.<\/p>\n