[MPlayer-users] use of libavcodec option aspect= and -vop crop

Catalin Muresan 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
and 4:3.

	check this link also http://www.divx.com/support/guides/guide.php?gid=12

 > cheers,
 > csincock at yahoo dot com


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