[MEncoder-users] -ss seek position?

[jthompson]

Thank you for the reply!

I agree fully with your conclusion. Not to dis Mencoder - I've used it many times in the past with much joy. This was my first attempt with -ss though. I have tried two alternatives first vlc and after a little trouble got what I wanted though not quite as accurate as I would like. And secondly, just before seeing you had responded, I tried ffmpeg. Once again joy. -vframe works perfectly. 

Thank you for the I-Frame math. I'm in NTSC land so a little adjustment and it'll work great.

Thanks again!



> Date: Tue, 10 Jun 2008 07:04:34 +0200
> From: belcampo at zonnet.nl
> To: mencoder-users at mplayerhq.hu
> Subject: Re: [MEncoder-users] -ss seek position?
> 
> jthompson wrote:
> > Hi all!  I'm haveing a problem getting mencoder to recognise the -ss parameter. I'm using XP sp2 and the string I'm using is:
> > 
> > mencoder -ss 00:00:00 -endpos 00:00:05 -nosound -ovc copy SOURCE_FILE.mpg -of mpeg -o OUT_FILE.mpg
> > 
> > The behavior is quite odd. With start / stop :00/:05 mencoder returns 5.005 secs and 150 frames writtenm, :01/:05 returns the same 5.005 secs and 150 frames, :02/:05 returns 4.505 secs and 135 frames, :03/:05 returns 3.505 secs and 105 frames, :04/:05 returns 3.003 secs and 90 frames and :05/:05 returns 2.002 secs and 60 frames. My .mpg test clip is only 6 seconds but I have tried longer clips.
> > 
> > I've also tried it with a different mpeg, a mpeg encoded avi and a dv encoded .mov . They all exhibit really strange behavior though a couple times things did seem to go right ( the number of frames were correct - i just watched the console output) but I could not duplicate it. I've tried this out on 4 different computers and am having no luck. I appreciate any help that can be offered.
> Conclusion mencoder sucks on -ss and -endpos. So does mplayer
> Try mplayer -ss , from the command line, for you it is in DOS window, 
> and watch the time codes if you change the values of -ss.
> use ffmpeg, at least my self compiled version is reliable. Further if 
> you are in PAL land, your source will have 25fps and if its DVB then 
> every 12th, after 0.48 sec. you get an I-Frame.
> 
> You always have to start WITH and end BEFORE an I-Frame
> 
> The endpos function works like start at 00:00:00 till and INCLUDING 
> 00:00:05 the start of the 5th second, till the next I-Frame.
> 
> If you want simple math, make your start and stop places at multiples of 
> 6 seconds, or 1.2 seconds, or 10 * 6 sec. so at min. points.
> 
> ffmpeg also has -ss 00:00:00 -vframes 25 ... ..
> and you'll get exactly 1 sec.
> > 
> > Best!
> > dh
> > 
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