[MEncoder-users] compression: 1080i versus 720p

[RC]

On Sun, 20 Dec 2009 04:46:18 -0600
Andrew Berg <bahamutzero8825 at gmail.com> wrote:

> What does deinterlacing have to do with framerate?

1080i at 30fps video is essentially 1920x540 at 60fps.  There are some small
differences in how 30fps interlaced vs 60fps progressive video is
captured, but they are really quite similar.

> but 1080i feeds are 30fps whether they've been deinterlaced or not.

Interlaced video is measured in fields.  NTSC is 60Hz (PAL is 50Hz) or
60 fields per second.  It's merely an easy oversimplification to call it
30fps, because they happen to combine two fields into a single MPEG
frame.

You can use the tfields filter to expand out the fields in 1080i to
get half-height 60fps.  Or inversely, you can use tinterlace to combine
two frames of 720p into double-height 30fps interlaced video (and then
presumably run them through yadif or similar to reduce it to a real
30fps progressive picture).


-- 
Ha. I'm the idiot.