[MPlayer-users] About 23.98 -> 25 fps (and others) framerate conversions
Julián Nuñez
julian at proteger.org.ar
Fri Dec 26 22:20:15 CET 2003
Hi.
I don't know if this mail belongs here or in dev-eng, I'll just drop it
here.
I will share some experience with playing different framerate movies at
25 fps, and some things I don't understand.
I'm a DXR3 user, and been using it for a half year now with mplayer, I'm
a mplayer user since 0.60.
I use my DXR3 in PAL norm, wich is 25 fps and since the beginning I
noted this "glitches" or -very- tiny pauses once per second with movies
encoded at 23.98 film framerate (most of them).
This "glithes" are the only problem I suffer, A-V sync and image quality
are both perfect. The problem is not present when I play 25 fps movies,
but those are rare.
Having tried every posible solution without success (changing FPS value
en lavc, disabling sound, every posible autosync value, compilers,
mplayer versions) I gave up.
Some days ago (16/12/2003 exactly) a thread called "converting 25fps ->
23.976 fps?" talked about using the -speed parameter. I think Rich
mentioned that. I tried that and...it worked! the command line was:
mplayer -vo dxr3 -vop lavc,expand=-1:480:-1:-1:1 -speed 25/23.978 movie.avi
Now the video plays smoothly as silk, and it's great.
This is what I think was happening: This glitches are the last frames
from every second staying twice the time, to "fill" the last 25th PAL frame.
What I think -speed 25/23.978 does is put a frame from the next second
in the last of the 25 frames, playing the video at 25 fps but faster.
Now, my questions (finally):
If I'm playing the video faster, it will take less to finish... this is
logical since this "pause" every second causes the movie to last longer,
so , which duration is correct, with or without the -speed parameter?
Also with the -speed parameter the sound changes it's hz, going from
48000hz to 52000 or so. Does this mean the sound is played faster? I
think so, it will be leaved behind othewise, am I correct?.
With a 30 fps movie, instead of this "tiny pauses", the video goes very
fast in the end of every second, I think those are the spare frames
caused by 30->25 fps conversion, so I've tried -speed 25/30, and the
video plays GREAT, but now the sound is slow, everthing is lower tone
(played at 36000 hz).
Can someone explain this a little better? Is there a way to fix this? Is
there a better way to correct this "glitches"?.
If this is the only way to fix the problem, I think it must be in the
manual.
Thanks for your time.
Julian.
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