[MPlayer-users] fast/slow scenes

[Alejandro Néstor Vargas]

Clemens Wächter dijo:
> Well that is not really something you have to tell to mencoder but more
> precisely something you need to tell the codec mencoder is using.
>
> I have tried 2-pass encoding using xvid and this was perfect for my
> needs in such situations. It just optimizes the bitrate use in the
> second pass and it does this perfectly selecting the perfect bitrate
> for every moment of the movie.

I was trying 2 passes encodings from last saturdy (it lastes about 8 hours
each try) but it seems that I obtain wrost results with 2 passes than 1 pass.
The file is smaller but the quality is ugly if I specifies 600 kbits the
file iscompressed at a average of 450 kbits with ugly quality, and if I specify 800
the file is compressed at 850 with good quality but in a 1 Gb file.

I extracted the difficult scenes and checked what is the bitrate needed for
this, and with 800 is enoug for obtaining the same quality that is in the
1 Gbquality. In the rest of scenes that are at least the 80% of the picture,
with 600is enoug to obtain the same quality as in the DVD.

> If you havent tried this, try it, it is great. If not please let us
> know -> which version of mplayer/mencoder are you using?
> -> what codec are you using?
> -> what commandline

I'm using pre5, Xvid_20020412

I don't remember exactly all the testes that I tryed, but something like
this:


mencoder -dvd 1 -ovc frameno -o frameno.avi

mencoder -dvd 1 -scale 640:480  -ovc lavc -lavcopts
vcodec=mpeg4:more_optionsvbitrate=600:vhq:vqmin=1:vqmax=31:vpass=1
-oac mp3lame -o h.avi

mencoder -dvd 1 -scale 640:480  -ovc lavc -lavcopts
vcodec=mpeg4:more_optionsvbitrate=600:vhq:vqmin=1:vqmax=31:vpass=2
-oac mp3lame -o h.avi

I tryed adding very high values of "vratetol=" to see if it is necesary for
letting mencoder to incress the bitrate to 800 or more if it is needed for
somescenes. I also aded vqdiff=31

I've tryed decressing the frame rate from the original 29.97 to 24 but I've
noticed the file generated seems to be larger, then I left the original
29.97.I've also tried to decress the size from 640x480 to 576x432 but the efect on
the file size was minimal.

-- 
Alejandro Néstor Vargas
anv at xnetcuyo.com.ar
ICQ: 20528995.
Departamento de Desarrollo
X Net Cuyo S.A.