Changing aspect ratio (reauthoring DVD)

[Pinstripes23]

Done and with success!

Thank you to everyone who gave their valuable hints to me!

BTW, I still have another DVD, which is authored incorrectly. I presume that it's neither 4:3 or 16:9 so in order to find out the right aspect ratio I should run Gspot, right? But how about those numbers which are in the crop command line of AVS file? How to determine the right values in order to get the aspect ratio fixed?

Well the display AR is either 4:3 or 16:9. Run the file through g-spot and also post a screenshot. You're thinking the picture itself might have a distorted AR.

The cropping numbers can be determined if you open the avs file(without resizing) in vdubmod:

video --> filters --> add --> null transform -- cropping

[stars]

Adding bars at the top and bottom after cropping them out will distort the AR if he is going for 16:9. To compensate he would have to add black borders to the left and right.

Well the aspect will not be destorted because the normal
DVD standard is 720x576 (PAL) and 720x480 (NTSC)

And here we have a video file which is a letterboxed 16:9 eg in a 4:3 format which
also have the format 720x576.

So the diffrence between 16:9 and 4:3 is that the picture in the movie have different sizes, but the
video format is the same 720x576.

The width is the same (720) the hieght differs. So the widescreen picture is streached when its viewed on the
tv screen...

The black bars at the sides have nothing to do with this.....

A film with the aspect 2.40:1 (PAL) has a hight of 300 pix but the videofile is still 720x576...

There are some Disney movies that have aspect 1.66:1 (PAL) the hight here is 434 pixels

So if his so called wiedscreen video clip has an aspect of 1.61:1 it will do fine becase the visual picture
is still 720x404 pixels (If it has that aspect)

No hard feelings Pinstripes23....

EDIT: If the width of the source isnt 720 then he must add black bars at the sides CORRECT !


Here is a link to a very informative site abput aspect ratios

http://lipas.uwasa.fi/~f76998/video/conversion/

And by the way
Im glad that you got it right Turbo Sensonic

stars....

[Alex_ander]

BTW, I still have another DVD, which is authored incorrectly. I presume that it's neither 4:3 or 16:9 so in order to find out the right aspect ratio I should run Gspot, right? But how about those numbers which are in the crop command line of AVS file? How to determine the right values in order to get the aspect ratio fixed?

If you have an already distorted picture from unknown source (you don't know how somebody cropped and resized it), you can only find correct displayed AR (it can be a non-standard one) experimentally by finding scenes with rounds, squares etc. and resizing (e.g. in VDub) for correct proportions. Knowing actual DAR (pixel ratio value providing undistorted image ) for your video, you can calculate resizing numbers for MPEG. DAR is the only necessary for calculations parameter of your video (the rest are standard numbers). I suggested a simple calculation table for any possible case in another thread:
https://forum.videohelp.com/topic333824.html
Alternatively (if you don't like calculations) you can use the popular FitCD utility.

[Pinstripes23]

Well the aspect will not be destorted because the normal
DVD standard is 720x576 (PAL) and 720x480 (NTSC)

That's the resolution. The aspect ratio is determined by the encoder and authoring prog. Besides you can't look at those numbers as 1:1 pixel AR because that is not how it is going to be displayed on a TV anyway.

And here we have a video file which is a letterboxed 16:9 eg in a 4:3 format which
also have the format 720x576.

So you agree that the picture is 1.78:1 inside the 4:3. So adding borders will distort the picture AR. You are forgetting that borders have to be contained within the 576 vertical resolution, so the vertical picture will get squashed down to 536 resolution. So when viewed on a TV it will be squashed vertically.

The width is the same (720) the hieght differs. So the widescreen picture is streached when its viewed on the
tv screen...

Not if it is encoded, authored, and your tv is set up correctly it won't.

The black bars at the sides have nothing to do with this.....

Never said it did(if you're talking about the original source). I said you must compensate by adding black borders to the sides if you are going to add to the top and bottom. This is after cropping away all the black.

So if his so called wiedscreen video clip has an aspect of 1.61:1 it will do fine becase the visual picture
is still 720x404 pixels (If it has that aspect)

But you agreed above it is 1.78:1 picture AR. So it isn't 1.61:1, so there's no point in bringing this up.

Here is a link to a very informative site abput aspect ratios

http://lipas.uwasa.fi/~f76998/video/conversion/

I have already done my research on the subject a long time ago. And I've been creating dvd's for some time now and have encountered all sorts of strange picture AR's as sources. And I have no problems correcting them using avisynth.

[Alex_ander]

cut of the black bars (if the pic have aspect 1.78 eg 720x404) add a 20 pix black bar at the top
and botton. This is for the overscan that the tv has. so you wont lose any picture...
reszie to 720x576 encode and author the DVD with the 16:9 flag

720x404 are suitable final resize numbers for ripping a 16:9 movie to smth. like divx (from both PAL or NTSC). In case of DVD pixel numbers are never related as 1.78:1 for a 16:9 video. For PAL letterboxed image they are 720x432 and for NTSC 720x360.

Adding bars at the top and bottom after cropping them out will distort the AR if he is going for 16:9. To compensate he would have to add black borders to the left and right.

True

[stars]

oops...

I must have been steping on somebodys toes....

@Pinstripes23

So you agree that the picture is 1.78:1 inside the 4:3. So adding borders will distort the picture AR. You are forgetting that borders have to be contained within the 576 vertical resolution, so the vertical picture will get squashed down to 536 resolution. So when viewed on a TV it will be squashed vertically.

Im not sure that we understand each other....

First of all we are talking about a video file that we really dont know much about..

What Im trying to say is that if you have a picture size of 720x404 we have an aspect ration of 1.78:1
which is full screen 16:9 (Im talking about picture size, the borders cut off)..

If we take the borders off and resize the picture to 720x576 which is DVD standard and
encode it with 16:9 flag. (You cannot encode it with the size 720x404)

Then we author the DVD as a 16:9 DVD....Then we would get a full widescreen DVD

The picture will not be destorted....(well if you look a the videofile in 4:3 mode it would look destorted)

as Alex_ander says there is a compensation for the overscan

For PAL letterboxed image they are 720x432

So if the picture was 720x404 there is a possibility to add black borders (letterbox) so you wouldnt
lose any picture with the overscan.


stars....

[Pinstripes23]

oops...

I must have been steping on somebodys toes....

not at all

First of all we are talking about a video file that we really dont know much about..

Actually we do. The resolution in the original screenshot he posted is 720x576. So we know he took a screenshot of the dvd as is. And from there you can manipulate how it will look by cropping, adding borders, resizing, etc.

What Im trying to say is that if you have a picture size of 720x404 we have an aspect ration of 1.78:1
which is full screen 16:9 (Im talking about picture size, the borders cut off)..

Actually if you cut off the borders(from the original screenshot) the size becomes 690x432 not 720x404. You shouldn't be looking at DVD resolution as 1:1 pixel ratio.

If we take the borders off and resize the picture to 720x576 which is DVD standard and
encode it with 16:9 flag. (You cannot encode it with the size 720x404)

Then we author the DVD as a 16:9 DVD....Then we would get a full widescreen DVD

The picture will not be destorted....

Ok I agree........but where was the add borders to the top and bottom you made in your previous posts? That was what I was disagreeing with. You made no mention of it just now. If you are going to add borders it will be part of the 576 vertical resolution like I said before.

as Alex_ander says there is a compensation for the overscan

For PAL letterboxed image they are 720x432

So if the picture was 720x404 there is a possibility to add black borders (letterbox) so you wouldnt
lose any picture with the overscan.


stars....

I think you are getting confused. 720x404 would be the AR if the PAR is 1:1. It has nothing to do with putting a picture within the 720x576 frame for DVD. Therefore you wouldn't use 720x404 when deciding if black borders should be added for overscan.

[stars]

Actually if you cut off the borders(from the original screenshot) the size becomes 690x432 not 720x404. You shouldn't be looking at DVD resolution as 1:1 pixel ratio.

Im sorry when I meant cuting of the border I meant the ones at th top and botton.

The ones at the left and right wouldnt show up anyway....

and for the overscan thing (adding borders) there is no need because of the hight of 432 pix..

So if I or (he) cut of the top and botton border we will get 720x432

And then resize it to 720x576 and encode it with a 16:9 flag....would this be right...???

stars...

[Pinstripes23]

So if I or (he) cut of the top and botton border we will get 720x432

And then resize it to 720x576 and encode it with a 16:9 flag....would this be right...???

Yes for the most part that would be right. As the original was a WS letterboxed encoded as 4:3.