[MPlayer-users] mencoder: Removing black bars creates blackli ne artifacts

[Francois Visagie]

> -----Original Message-----
> From: On Behalf Of Guillaume POIRIER
> Sent: 26 September 2007 09:55
> Hi,
> 
> On 9/26/07, Trevor Bradley <tgb at sfu.ca> wrote:
> > Hey everyone.  I love mencoder.. It's great for batching up 
> mpgs I've 
> > recorded with MythTV to convert to AVI.
> >
> > I've figured out how to remove the black bars at the top 
> and bottom of 
> > widescreen programming.  Presently I'm using the following 
> commands to 
> > transcode files:
> >
> > mencoder filename.mpg -quiet  -vf lavcdeint -vf 
> crop=704:352 -ovc xvid 
> > -oac mp3lame -xvidencopts pass=1 -o /dev/null mencoder filename.mpg 
> > -quiet  -vf lavcdeint -vf crop=704:352 -ovc xvid -oac mp3lame 
> > -xvidencopts pass=2:bitrate=1300 -o filename.avi
> 
> [..]
> 
> > Thanks for your help!  Any advice would be appreciated.
> 
> s/-vf lavcdeint -vf crop=704:352/-vf lavcdeint,crop=704:352/g
> 
> You may want to use yadif instead of lavcdeint too.

Excellent advice - those are interlacing artifacts you're seeing. Part of
the reason you only see lack of proper deinterlacing in your cropped video
(at the same physical display size) is probably because it has less vertical
pixel resolution (due to cropping).

The latest MPlayer documentation has a wealth of information on the
principles of cropping, scaling and deinterlacing, especially in section 14.
Here's an example: "Also, deinterlacing should be done after cropping [1]
and before scaling." Remember to try out additional deinterlacing mechanisms
and options as Guillaume suggests.

As an aside, from the documentation I had understood that a proper filter
chain is constructed either with the -vf filter1,filter2,...filtern
construct, or by using -vf-{add|pre|del|clr}. I'd therefore use one of those
approaches as opposed to the -vf filter1 -vf filter2 you have above.

Regards,
Francois





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