[MPlayer-dev-eng] BUG - incorrect fps detected on NTSC DVDs result in jumpy video

[Christian Lambert]

|
|> I noticed that mplayer doesn't correctly detect NTSC DVDs video
|> that are encoded in progressive mode (24fps) (which is the case
|> for 90% of NTSC movies)
|>
|> It will play those DVDs at the normal 30 fps which result in a
|> jumpy video especially during pan scenes or scenes with lots of
|> motion because fields are duplicated.
|>
|Yes, I noticed the same with some SVCDs.
|
|> The mpeg2 stream contains "repeat" flags on some fields to take
|> the original 24fps source and play it at 30fps so mplayer should
|> skip those repeat frames and play just the original 24
|> progressive frames.
|
|Well I think we need some logic to know which frames to skip, so we need to 
|know where the info which frames to repeat is stored in libmpeg2.
|I guess Arpi knows better about that code, than me :)
|
|-- 
|Best Regards,
|	Atmos
|

I know that xine and ogle already have this algorithm in it to play
only the FILM portion of the DVD and not the extra fields that
are just thrown in there to make it 30fps.  Actually, playing it
with 30fps is almost as bad as playing it in interlaced mode where
you don't get the true 24 progressive images.   I see that this bug
is still not fixed in the latest CVS I just pulled.   

I'm not really a programmer but I know how to read source code, so I 
started looking at the code but I can't figure out where the bug
could be coming from since there are calls to libdvdread involved here too. 
I think that the framerate code is in the header of the VOB and it
has a special mark when the DVD is encoded progressive (24fps) versus 
interlaced (29fps).   I think what's happening is that when you play
a PAL movie, you don't really notice this because there is only two
field duplicated to make it 25fps.   However in the NTSC world, it's
a greater problem because we have to duplicate lots of fields to convert
from 24 to 30fps on the fly, which is where those "rff" flags comes into
play to say which field to repeat in the mpeg2 video. 

Since 99% of the NTSC movies are encoded in progressive mode, I'm seeing
this on all my DVDs.  Altough maybe not everyone notices it, if you pay
close attention you really see the duplicated frames in a slow camera pan scene.

That's the only real bug that's preventing me right now from watching
DVDs in mplayer with nice and smooth playback. 

If nobody has the time to look at this, could you at least let me know
all the relevant source file that I should check regarding this bug. 

Thanks

-Christian