[MEncoder-users] Encoding iPhone MOV into MPEG-2 -- Video framerate is super fast!?

[Jarred Nicholls]

Wow that actually is working!  I used -mc 0 and figured since that didn't
work there was no hope.  LIterally -mc 0.1 is the only thing changed and now
all of a sudden it's fine.  How does that help the situation when mencoder
(and ffmpeg actually) doesn't correctly identify the source's variable
framerate?

So yeah, after using -mc 0.1, it is no longer showing the same problems as
before...however, the audio is slightly behind the video.  Between 500ms and
1sec I'd say.  I did something funky as a workaround, but not sure if it
will be a universal workaround.  It did work surprisingly well however:  I
used ffmpeg to copy the MOV's audio and video and mux it into an AVI
container verbatim.  I then used the same exactly mencoder command with "-mc
0" added to it, and the resulting MPEG-2 was spot on.  I'd prefer to make
mencoder work in one shot, so is there anything else I can do to help the
a/v sync after adding "-mc 0.1"?  Maybe -nobps?

I'm not cropping but I do need to scale to bring the "rotated" height down
to 480 to fit onto a 720x480 stage.  That is NTSC DVD compliance and my
optimal output.

Thanks a lot for your help Laine,
Jarred

On Tue, Nov 10, 2009 at 11:35 PM, L Lee <llee040 at sbcglobal.net> wrote:

> On 11/10/09 9:13 PM, "Jarred Nicholls" <jarred.nicholls at gmail.com> wrote:
>
> > Hi everyone,
> >
> > Firstly I appreciate you all taking the time to help with this issue.
>  Maybe
> > it will stand out as an obvious or simple solution to someone.
> >
> > I am encoding a video taken from an iPhone 3GS (h.264 video, MOV
> container
> > at 90 degree rotation/transformation matrix in the tkhd header). I have
> had
> > troubles encoding this type of video into DVD compliant MPEG-2 video
> using
> > mencoder (no issues with ffmpeg), but for this type of video I need
> mencoder
> > strictly for the expand and rotate filters.  The resulting MPEG-2 video
> is
> > super fast (every 2 out of 5 frames are dropped/skipped when encoding)
> and
> > the audio after muxed with the video is at its original speed.  It's
> almost
> > like the frame rate is super fast (~50+ fps), but definitely has
> something
> > to do with the frames being dropped.  MediaInfo reports the average fps
> is
> > 19 (the video is variable fps).
> >
> > Here is the command I run:
> >
> > mencoder -oac lavc -ovc lavc -of mpeg -mpegopts format=dvd:tsaf -vf
> > rotate=1,expand=720:480,harddup -srate 44100 -af lavcresample=44100
> > -lavcopts
> >
> vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9800:vbitrate=5000:keyint=18:v
> > strict=0:acodec=ac3:abitrate=192:aspect=4/3
> > -ofps 30000/1001 -o test2.mpg IMG_0018.MOV
> >
> > Here is a link to the source video and the result video respectively:
> >
> > http://www.bcam.org/tmp/IMG_0018.MOV
> > http://www.bcam.org/tmp/test2.mpg
> >
> > I have tried several alterations to the command above.  One in particular
> > was to simply remove the explicit -ofps setting to see if it would simply
> > keep the original video's framerate...and it errored out saying "MPEG1/2
> > does not support 617/12 fps" which is approximately 51.41fps.  This would
> > explain the skipped frames and the video speed up, but why is it reading
> > 51.41fps when the original video is (on average) only 19fps?
> >
>
> What happens if you add -mc 0.1 to the end of your command line?
> Don't you want to crop vertically to preserve aspect ratio? Try
> "crop=480:540:0:32" right after your "rotate" filter.
>
> Laine Lee
>
>
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