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

[Jarred Nicholls]

On Wed, Nov 11, 2009 at 9:34 AM, L Lee <llee040 at sbcglobal.net> wrote:

> On 11/10/09 11:06 PM, "Jarred Nicholls" <jarred.nicholls at gmail.com> wrote:
>
> > 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?
>
> Don't' look a gift frame in the pixel. I can say that because I'm in Texas.
> (In other words, I don't know.)
>

Fair enough :-)


> >
> > 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?
>
> Are you using Mac OS X (I wondered because of the format of your command
> line)? If so I can send you an Automator workflow to let you apply an
> offset, which you specify when the workflow is run, to an mpg file with ac3
> audio. I can also send you an AppleScript droplet that employs the
> ffmpeg/sox workflow mentioned a few weeks ago on this list to brighten the
> tempo of an ac3 file using a factor based on an amount that you enter in
> milliseconds when you drop the ac3 file on the droplet's icon.
>

I'm on debian/ubuntu, but I run os x on my dev box.  I can convert any
script to a bash/ruby/python/etc. script so maybe just having the workflow
would be helpful, thanks!  I am unfamiliar with the ffmpeg/sox workflow, I
wasn't on the list until yesterday.  What was the subject titled?  I can
search for it in the archives.


>
> >
> > 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.
>
>
> The crop values I provided preserve aspect ratio while cropping enough
> (leaving wide enough pillar bars) to preserve most of the original frame. I
> would prefer to take a 4x3 chunk out of the vertical middle of the video
> and
> make it big enough to fill a standard DVD frame. Here's an example that
> keeps aspect ratio mostly intact but slides the frame above center enough
> to
> keep most of your subject in the frame. It's sort of a vertical pan and
> scan. Replace your "expand " filter with "crop=480:360:0:96,scale=720:480".
>

Thanks, I'm with you.  I would do the same, but I'm going for more of a
"universal" approach...I will be handling all kinds of video with unknown
properties in an automated fashion, not knowing where the subject of the
video is focused, etc.  Maybe not the best approach from a production
standpoint, but from an "adaptability" or "flexibility" approach, I think
it's best that I preserve the entire original frame inside the output.  I
may be stretching this particular video wider, but if it's at a 4/3 aspect
ratio, the 4/3 television will squish it back to normal.  However, I am
probably going to go all 16/9 no matter what, so in that case it definitely
would be a breach of original aspect ratio when viewed.  Not exactly sure of
the best way to handle that other than cropping like you suggest.  This type
of vertical video will be somewhat seldom, but I still need to handle it
nevertheless.

What I'm very interested in is a sox workflow to normalize the ac3 audio.  I
have had lots of success with a/v syncing using my AVI mux approach, so
timing (currently) is not an issue...I'm losing about .5 seconds of video,
however visually I can't actually notice anything being lossed.  What I have
noticed is that the resampling of the audio to ac3 is bringing the volume
down.  I think sox would be perfect for increasing the volume of the audio
stream.  I could hook in sox in front of mencoder and use pipes to feed
mencoder, but I wouldn't know the best way to go about it.  Maybe the
ffmpeg/sox workflow mentioned earlier would help.


>
> Laine Lee
>

Thanks a lot Laine,
Jarred


>
>
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