How does DCP-o-matic deal with different video frame rates?
DCPs have a limited allowed range of frame rates; currently,
DCP-o-matic assumes that the output DCP can be 24, 25 or 30fps.
If the source video is not in one of these rates, DCP-o-matic will
try a few tricks:
- If the frame rate is half of one of the DCP rates (i.e. 12, 12.5
or 15fps), each frame will be duplicated in the output.
- If the frame rate is double one of the DCP rates (i.e. 48, 50 or
60fps), every other frame will be dropped from the output.
- Otherwise, DCP-o-matic picks the nearest available frame rate from the list we have so far (12, 12.5, 15, 24, 25, 30, 48, 50, 60fps). It will run the DCP at
this rate (or half or double it, as appropriate), meaning that the video will be run faster or slower than in the original content. To compensate for this, the
audio is the resampled in such a way that it will be in sync with the video at the same (new) speed. The practical upshot of this is that for frame rates close
to a DCP rate (24 fps drop-frame, for example) the content will be run (imperceptibly and slightly) too fast.