[MPlayer-users] -ss Does it work? Also bpp. Bunkus explain maybe?

Geoffrey Trexler skynet at charter.net
Mon Jan 13 04:22:52 CET 2003 

On Sun, 12 Jan 2003 21:53:51 -0500
D Richard Felker III <dalias at aerifal.cx> wrote:

> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> On Sun, Jan 12, 2003 at 09:17:52PM -0500, Geoffrey Trexler wrote:
> > [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> > Does the start position (-ss) work? I'll show you the options I'm using.
> > 
> > cat *.vob | nice -+19 mencoder -aid 128 -oac mp3lame -lameopts
> > vbr=3:br=128 -ofps 23.976 -ovc lavc -lavcopts
> > vcodec=mpeg4:vhq:vbitrate=1608:vqmin=2:vqmax=31:vpass=1 -vop
> > scale=528:-2 -ss 00:00:21 -endpos 01:55:50 -; cat *.vob | nice -+19
> > mencoder -aid 128 -oac mp3lame -lameopts vbr=3:br=128 -ofps 23.976
> > -ovc lavc -lavcopts
> > vcodec=mpeg4:vhq:vbitrate=1608:vqmin=2:vqmax=31:vpass=2 -vop
> > scale=528:-2 -ss 00:00:21 -endpos 01:55:50 -
> 
> Of course -ss doesn't work on non-seekable streams such as pipes. WHY
> ON EARTH are you copying vob files and then cating them to mencoder to
> encode?? PLEASE EVERYONE! There's a reason mplayer/mencoder have a
> -dvd option. It works MUCH better than trying to play vob files.
> 
> Also if you simply CAN'T use -dvd with mencoder (for example if the
> DVD drive is on a different computer, still DO NOT COPY THE VOBS!
> Instead use mplayer -dumpstream to get the entire DVD as one decrypted
> file and encode from it.
> 
> > Ok about the bits per pixel. I put this in:  perl ../../calcbpp.pl 720x466 1.78 1608 29.97
> > 
> > Prescaled picture: 1025x466, AR 2.20
> > 720x320, diff   7, new AR 2.25, AR error 2.21% scale=720:320 bpp: 0.233
> > 704x320, diff   0, new AR 2.20, AR error 0.01% scale=704:320 bpp: 0.238
> > 688x320, diff  -7, new AR 2.15, AR error 2.33% scale=688:320 bpp: 0.244
> > 672x304, diff   1, new AR 2.21, AR error 0.47% scale=672:304 bpp: 0.263
> > 656x304, diff  -6, new AR 2.16, AR error 1.96% scale=656:304 bpp: 0.269
> > 640x288, diff   3, new AR 2.22, AR error 0.99% scale=640:288 bpp: 0.291
> > 624x288, diff  -4, new AR 2.17, AR error 1.55% scale=624:288 bpp: 0.299
> > 608x272, diff   4, new AR 2.24, AR error 1.57% scale=608:272 bpp: 0.324
> > 592x272, diff  -3, new AR 2.18, AR error 1.09% scale=592:272 bpp: 0.333
> > 576x256, diff   6, new AR 2.25, AR error 2.21% scale=576:256 bpp: 0.364
> > 560x256, diff  -1, new AR 2.19, AR error 0.58% scale=560:256 bpp: 0.374
> > 544x240, diff   7, new AR 2.27, AR error 2.93% scale=544:240 bpp: 0.411
> > 528x240, diff   0, new AR 2.20, AR error 0.01% scale=528:240 bpp: 0.423
> > 512x240, diff  -7, new AR 2.13, AR error 3.13% scale=512:240 bpp: 0.437
> > 496x224, diff   1, new AR 2.21, AR error 0.64% scale=496:224 bpp: 0.483
> > 480x224, diff  -6, new AR 2.14, AR error 2.67% scale=480:224 bpp: 0.499
> > 464x208, diff   3, new AR 2.23, AR error 1.37% scale=464:208 bpp: 0.556
> > 448x208, diff  -4, new AR 2.15, AR error 2.15% scale=448:208 bpp: 0.576
> > 432x192, diff   4, new AR 2.25, AR error 2.21% scale=432:192 bpp: 0.647
> > 416x192, diff  -3, new AR 2.17, AR error 1.55% scale=416:192 bpp: 0.672
> > 400x176, diff   6, new AR 2.27, AR error 3.19% scale=400:176 bpp: 0.762
> > 384x176, diff  -1, new AR 2.18, AR error 0.84% scale=384:176 bpp: 0.794
> > 368x160, diff   7, new AR 2.30, AR error 4.34% scale=368:160 bpp: 0.911
> > 352x160, diff   0, new AR 2.20, AR error 0.01% scale=352:160 bpp: 0.953
> > 336x160, diff  -7, new AR 2.10, AR error 4.77% scale=336:160 bpp: 0.998
> > 320x144, diff   1, new AR 2.22, AR error 0.99% scale=320:144 bpp: 1.164
> > 
> > I don't really understand what all this means. For example diff -4
> > ???, and AR error ??? Could someone explain this in detail to me?
> 
> AR = aspect ratio, AR error = how much the aspect ratio is off by if
> you use those dimensions. You can't get the exact aspect you want
> unless you make width and height not divisible by 16, but that will
> lower quality. Also these numbers look a bit fishy...are you sure
> you're using the script right?
> 
> > I'm trying to encode a good DVD Quality Spiderman onto two 700MB
> > CD's. That's my goal. It looks really nice in the low motion scenes
> > with the settings I have above, however in the high motion scenes it
> > doesn't look that great. BTW the movie is 121 minutes long, but I'm
> > going to cut some of it, which is why I'm trying to get the -ss to
> > work. So it should turn out to be about 115 minutes long. Maybe this
> > will help in your calculations.
> 
> With the bitrate you have it should look nearly identical to the DVD.
> However you're not cropping the black borders it seems, so that will
> lower quality quite a bit! Use -vop cropdetect with mplayer first to
> figure out crop values, then tighten them in a little bit to make sure
> you get rid of all the border.
> 
> Also read the docs and the encoding tips file.
> 
> Rich
> 
> _______________________________________________
> RTFM!!!  http://www.MPlayerHQ.hu/DOCS
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Ok well I don't have much of a choice with the vob's because I don't have the DVD anymore, perhaps I can cat them into one big vob, and bypass the |.

About the not using the script right, I looked at my prescale thing, and it said 1.78:1. Here's that line Movie-Aspect is 1.78:1 - prescaling to correct movie aspect. 720x466 is what I got from crop detect. I found the 29.97 from -v with mplayer. The 1608 being the bitrate. So I used perl ../../calcbpp.pl 720x466 1.78 1608 29.97 Is this not the correct way to use it?

Here's a few lines from cropdetect

crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.7% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.7% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.7% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.7% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.6% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.6% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.6% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.6% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.6% 0 0 0%
crop area: X: 0..719  Y: 4..470  (-vop crop=720:466:0:4)6%  5.6% 0 0 0%

So with this information how would I use the cropping filter? I'm new to this so these questions may seem quite stupid to you. I've looked at the man page on this, but I can't really understand it.

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