[MEncoder-users] DVD creation problem, settop player cuts off boarder

karl-heinz-1950 at web.de karl-heinz-1950 at web.de
Mon Mar 23 22:45:56 CET 2009


I tried to run these options and I still don"t understand what is happening, you run this command

-vf scale=720:480,expand=-64:-32:32:16

where 720:480 is the full NTSC resolution, so you don't scale down do you? What is the resolution of your input material? 

Option 1:
If the scale filter scales down and the expand should end with NTSC 720:480 I would expect this:

scale=656:448 -> picture is scaled down
expand=-64:-32:32:16 -> picture has again 720:480 pixels due to the black bars (left and right 32 pixels, top and bottom 16 pixels)

Because of the scaling down I have a degree in quality (if recognizable by the human eye or not may be another story) Out of 720:480 picture I make 656:448  picture.

Option 2:
Or if your input material is 720:480 and you run this command your output is larger than 720:480 and this wouldn"t conform to the NTSC standard.

Are my thoughts wrong? I believe you that you are right, I just want to understand it. There are many different NTSC resolutions, do you always use the same size for the black border?

Can you please shed some light into this issue? Maybe it would be start if you could give me the information what resolution your material in the single stages has? (Please indicate the size with and without the black bars).

Thanks a lot for your patient help!

> -----Ursprüngliche Nachricht-----
> Von: "Phil Ehrens" <phil at slug.org>
> Gesendet: 22.03.09 00:00:29
> An: MEncoder usage discussions <mencoder-users at mplayerhq.hu>
> Betreff: Re: [MEncoder-users] DVD creation problem, settop player cuts off boarder

> karl-heinz-1950 at web.de wrote:
> > Let me see if I understood this correctly:
> > 
> > My recording has 720x576 pixels (full of "information" no black boarder), correct? My TV thinks that all these pixels occupy the overscan area and instead of displaying possible strange things, e.g. green bars, in that area it rather cuts off the picture?
> > 
> > So using the -vf scale=720:576,expand=-64:-32:32:16 it would do
> > 
> > scale: shouldn"t do anything since my input is already on this resolution
> > expand: adds a black border around the picture
> > 
> > The result would be a picture larger 720x576 and thus violating PAL standard, wouldn"t it? Or does it first the expand (though second in the chain), so it enlarges the picture and it scales it back to the PAL standard? If that happens the viewable amount of pixels is reduced - which shouldn"t happen.
> As I said, you can use the options with mplayer to preview exactly
> what they do. They scale down the video to fit in the viewable
> area, and add black bars which are in the overscan zones. It might
> sound strange, but it's the right thing to do if you want to see
> the entire picture.
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