View Single Post
Old 5th June 2018, 09:25   #8  |  Link
manono
Moderator
 
Join Date: Oct 2001
Location: Hawaii
Posts: 7,406
The difference is due to the drop frame flag. DVD players use 30fps and something like DGIndex uses 29.97fps. The fps difference accounts for the player showing the film to be about 5 seconds shorter in length. You can look it up but the Wikipedia says this:

Quote:
This meant that an "hour of timecode" at a nominal frame rate of 30 frame/s, when played back at 29.97 frame/s was longer than an hour of wall-clock time by 3.6 seconds, leading to an error of almost a minute and a half over a day.

To correct this, drop frame SMPTE timecode was invented. In spite of what the name implies, no video frames are dropped (skipped) using drop-frame timecode. Rather, some of the timecodes are dropped. In order to make an hour of timecode match an hour on the clock, drop-frame timecode skips frame numbers 0 and 1 of the first second of every minute, except when the number of minutes is divisible by ten (i.e. when minutes mod 10 equals zero). (Because editors making cuts must be aware of the difference in color subcarrier phase between even and odd frames, it is helpful to skip pairs of frame numbers.) This achieves an "easy-to-track" drop frame rate of 18 frames each ten minutes (18,000 frames @ 30 frame/s) and almost perfectly compensates for the difference in rate, leaving a residual timing error of only 1.0 ppm, roughly 2.6 frames (86.4 milliseconds) per day.
https://en.wikipedia.org/wiki/SMPTE_...frame_timecode
manono is offline   Reply With Quote