[MPlayer-users] use of libavcodec option aspect= and -vop crop
catalin.muresan at astral.ro
Thu Feb 6 08:14:35 CET 2003
On Thu, Feb 06, 2003 at 02:05:23AM +1030, Chris Sincock wrote:
> I am still not sure which is the best way to go, ie
> - leave the bands, no (or conservative) cropping and use aspect=
> - crop the black stuff, do a bit of calculation, rescale one
> dimension, and use aspect=
> or - crop the black stuff and just rescale the movie to the correct
> size, and don't use aspect=
or - crop the black bands and use aspect.
i had a 720x480 DVD which i cropped to 704x352 (multiples of 16)
original aspect was 1.78. so:
720 / 480 = 1.50 which needs to be scaled to 1.78 for playback which
means multiply by 1.78/1.50 = 1.186
i cropped to 704/352 = 2.00 which needs to be multiplied by 1.186
2.00 * 1.18 = 2.36 so i went with aspect 2.35:1 (encoded with aspect=2.35)
at playback mplayer does:
Movie-Aspect is 2.35:1 - prescaling to correct movie aspect.
VO: [xv] 704x352 => 828x352 Planar YV12
i hope i am not _completely_ wrong with this math, afterall, the
rips look natural.
> I eventually went with option 1 after trying the different methods
> as it looked to me like it produced the best video quality for a
> given bitrate.
i ripped to 2 CDs so i used -ovc frameno
> originally I just tried aspect=<a calculated value> to correct the
> difference, but it only accepts a few fixed aspects.
i don't think there are many aspects "out there", only 2.35, 16:9
check this link also http://www.divx.com/support/guides/guide.php?gid=12
> csincock at yahoo dot com
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