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#1 2007-08-18 06:09:20

sH
Member
From: Braunschweig, Germany
Registered: 2007-05-02
Posts: 145

mencoder: anamorphic 16:9 -> cropped 4:3

Hello friends,

I'd like to convert a Movie in anamorphic 16:9 to 4:3 fullscreen (cropped left & right).
Can anyone tell me what parameters I need for mencoder to do this?

Thanks.

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#2 2007-08-18 21:37:05

Klepper
Member
From: Nürnberg, Germany
Registered: 2007-08-18
Posts: 21

Re: mencoder: anamorphic 16:9 -> cropped 4:3

the parameters are 'crop' and optionally 'scale', i.e.

-vf crop=newwidth:newheight[:offsetfromleft:offsetfromtop]  (offset-stuff is optional, new picture will be centered if not given) and
-vf scale=newwidth:newheight

or both in one line
-vf crop=newwidth:newheight,scale=newwidth:newheight


Example:
source is VO: [xv] 704x544 => 1006x544
you want to keep quality so you only reduce the width
4:3 will be 726:544, as the aspect ratio is kept you will have to crop to 507:544
-> mencoder -vf crop=507:544 ...
This way you will have to tell the playing program to play back at 4:3, i.e. mplayer -aspect 1.33 ... or -aspect 4/3

To get to a real 4:3 file use 'scale'
-> mencoder -vf crop=507:544,scale=720:544 ...  (I put 720 instead od 726 to keep it modulo16)

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#3 2007-08-20 06:09:36

sH
Member
From: Braunschweig, Germany
Registered: 2007-05-02
Posts: 145

Re: mencoder: anamorphic 16:9 -> cropped 4:3

Thank you. I'll try it out.

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#4 2007-08-20 18:17:21

sH
Member
From: Braunschweig, Germany
Registered: 2007-05-02
Posts: 145

Re: mencoder: anamorphic 16:9 -> cropped 4:3

Klepper wrote:

source is VO: [xv] 704x544 => 1006x544
To get to a real 4:3 file use 'scale'

-> mencoder -vf crop=507:544,scale=720:544 ...  (I put 720 instead od 726 to keep it modulo16)

Maybe you can explain this? I don't know wheres the difference between the two scales.
how can I crop to 507 and afterwards scale to 720 ? Won't I lose quality then?

Thanks.

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#5 2007-08-26 11:22:29

Klepper
Member
From: Nürnberg, Germany
Registered: 2007-08-18
Posts: 21

Re: mencoder: anamorphic 16:9 -> cropped 4:3

after croppping the video is still anamorphic, i.e. 507:544 and the player will still have to resize it at playback.

If you want to have a non-anamorphic file you either need to decrease height(507:380 or better 496:372 to keep it modulo16 which goes easier on the encoder) or increase width (720:544).
decreasing the size will definitely decrease quality. Increasing size will either need a higher bitrate for the same quality or have worse quality when the bitrate is kept than the anamorphic file

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