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

[Jarred Nicholls]

Just to append to my last message: the a/v is a little out of sync because
the resulting video is about a full second shorter in length from the audio.
 I noticed skipped frames at the beginning of the encoding process.  I'll
try forcing "-noskip" and worse case i'll just stick with the AVI mux
workaround.

Thanks,
Jarred

On Wed, Nov 11, 2009 at 12:06 AM, 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?
>
> 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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>
>