[MEncoder-users] low quality decrypt

[Pete Davis]

> Hi,
> 
> On 9/21/05, Pete Davis <pete at petedavis.net> wrote:
> > > > the marvelous MPlayer documentation found at
> > > > http://www.mplayerhq.hu/DOCS/HTML/en/index.html .
> > > > Pay special attention to chapters 7 and 8, which go into detail on
> the
> > > > mysteries of video encoding using MEncoder.
> > >
> > > Really, I tried to do so. But i simply couldnt understand much. My
> > > problem is that i know nothing about image/video processing. To be
> > > honest, i tried with the spanish version, but i see now it is some out
> > > of date. And i get lost with the english version.
> > >
> > > However, the real problem _for me_ is, imho, the high level (or not
> > > for novice) of the help. I think it requires a previous knowledge of
> > > video stream, formats, etc etc
> > >
> > > Newcommers, like me, just pretend to decryp a dvd without having a
> > > deep knowledge of all the posibilities that mencoder provides.
> > >
> > > As time goes by, i will try to impruve my output files, once i get a
> > > deeper knowledge and practice with mencoder.
> > >
> >
> > Miguel, I agree, as a beginner, I found the documentation very hard to
> > follow because you do really need to understand quite a bit about video.
> >
> > I found that simply trying to encode a bunch of different things,
> reading
> > about and trying different parameters, and looking at the results, thing
> > slowly started to make more sense to me. It does take a while to start
> > feeling comfortable with all the terminology and different things you
> need
> > to know.
> >
> > For encoding DVDs, you really need to read through Chapter 8
> (unfortunately
> > it hasn't been translated into the Spanish version!).
> 
> If you are willing to translate it, I'm sure that this will be greatly
> appreciated.
> 
> 
> [..]
> 
> > Unfortunately, the example in the Spanish docs (7.1 Codificacion MPEG-4
> en 2
> > or 3 pasadas) is not a particularly good example. It does a 2 pass
> encoding
> > but does a 3rd pass for audio which isn't necessary.
> >
> > Modifying their example, I would do something like this instead:
> >
> > Pass #1:
> >
> > mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -oac copy -o
> > /dev/null
> >
> > Pass #2
> >
> > mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -oac mp3lame
> > -lameopts vbr=3 -o pelicula.avi
> 
> I do not think this is a good example, though I have not double
> checked myself: you should process "almost" the same audio data on
> both pass, otherwise you may/will end-up with A/V desync.
> 
> You may for example do -oac mp3lame -lameopts vbr=3:aq=9 on first pass
> to reduce the amount of time sucked up by the mp3 encoding.
> 
> 

Guillame, I don't know about the inner workings of mencoder, but almost
EVERY encoding I've done for the past several months has had -oac copy for
the first pass and -oac mp3lame ... for the second pass. This includes
mpeg-2 to mpeg-4 conversion from my hauppauage capture card, DVD to mpeg-4
encodings, as well as mpeg-4/AC3 to mpeg-4/MP3 encodings.

I have never once experienced audio-video desync with any of my conversions
using this method.

That's not to say it's not possible. I'm sure you know better than I. But I
have never experienced it over a pretty wide range of encodings.

Pete