[MEncoder-users] Changing frames per second

[Ross Clement]

I'm considering buying a digital camera with movie mode. This will allow me
to always have a "video" camera to hand instead of the borrowed camera I use
sometimes at the moment. However, pretty well any still cameras with "movie"
mode record at ~30fps instead of the 25fps of PAL video.

Clearly I could author all my DVDs as NTSC videos, but then I lose some
vertical resolution. Also there would be difficulties if I mix ~30fps and
25fps content. I think.

I had read that changing frames-per-second of video was problematic as
dropping a number of frames per second

I had a go at downloading some ~30fps video clips from the internet and
converted them to 25fps. A sample command is:

mencoder 1_hi.mov -of mpeg -mpegopts format=dvd:tsaf -ovc lavc -oac lavc
-lavcopts vcodec=mpeg2video:acodec=ac3:vbitrate=1000:aspect=4/3 -ofps 25  -o
junk.mpeg

I was surprised by how good the resulting quality is. I couldn't see any
unnatural jerkiness of movement.

I've searched through the MPlayer html docs, and can't find anything about
how frame rate conversions are done. Though I notice the frequent "skipping
frame" output while encoding. So I presume that the conversion hard-drops
frames.

Can anyone tell me how frame rates are converted? And are there any higher
quality techniques built into mencoder that I could use that might achieve a
higher quality result?