movie loaded with VirtualDub+AviSynth gets 'stretched'

[aldaco12]

Hi.
I hope I'll treceive help, since my topic is rather singular.

I'm using AviSynth to 'teach' VirtualDub how to load D2V files, so I can

1) rip a DVD
2) use AVI2DVD to make a D2V file
3) load with VirtualDub the file 'LoadD2V.avs', which is written:

MPEG2Dec3dg_mpeg2source("C:\mc\Tmp\mov\dvd\Movie.d 2v")
ConvertToYUY2()

so I can create an AVI using VirtualDub; I apply the filters:
- Deinterlace, to deinterlace the video
- Nulll Transform + 'cropping', to set some positive offsets and to crop the black bars, if needed
- Resize, to resize the movie screen wich results from the use of the 2 filters above mentioned into a more appropriate size.

The result of all this is that the AVI obtain is somewhat 'stratched', so its shapes are more 'oval' than 'round' (an O becomes an oval a little tall).

It is very strange, to me, since my use of the filter Resize is to produce a movie of resolution:
X' = constant * (720 - cropE - cropW)
Y' = constant * (576 - cropN - cropS)
(I live in a PAL country, and DVD specs are 720x576)
Obviously, "constant" is a constant, and the numbers I use as "cropX" are the pixels I crop when I use the Null transform filter to remove the black bars.

Why the screen seem a little taller than what it should be even if y use of the filter "Resize" should keep aspect ratio? Is it a wrong usage of AviSynth?

Thanks for helping me.

[jagabo]

You could use VirtualDubMPEG2 or VirtualDubMod which can read VOB files directly.

VirtualDub (and all the variants) display video with square pixels. Your DVD source doesn't use square pixels. Hence the stretched picture. With MPEG files the display aspect ratio is independent of the frame size. Your 720x576 VOB files are either 4:3 or 16:9 (before removing the black bars). You could resize first, then cut off the black bars. For example a 4:3 video could be resized to 640x480 (note 4x3 ratio) then the black bars cropped. A 16:9 could be resized to 640x360 (16x9 ratio) and then cropped.

[aldaco12]

Thanks for these useful hints!
So, if I well understood, I can just resize the movie according on its aspect ratio (for example, I use DVD2AVI to extract the D2V and the inormation on the aspect ratio comes from there) and resizing the DVD into:
- 640x480 an 4:3 aspect ratio movie
- 640x360 a 16:9 aspect ratio movie ?
(and I must remove the black bars LATER)
If it's so, good! Am I correct?

But....are the DVD movies only 4:3 or 16:9? I thought there were many possibiliities ad I wondered why DVD2AVI ony showed 4:3 and 16:9.

[jagabo]

I use DVD2AVI to extract the D2V and the inormation on the aspect ratio comes from there) and resizing the DVD into:
- 640x480 an 4:3 aspect ratio movie
- 640x360 a 16:9 aspect ratio movie ?
(and I must remove the black bars LATER)
If it's so, good! Am I correct?

Yes, that is correct. You can crop first but then it's harder to figure out the right dimensions for resizing. Actually, it's better to crop first and resize. It's faster since the program won't have to waste time resizing the black bars in addition to the picture, and it avoids the problem of resizing artifacts between the picture and the black bars.

The easiest way to figure out the appropriate size is to set it up the first way (resize then crop), note the final frame size, the reverse the two operations. For example, say you resized to 640x360, and after cropping 640x272 was left. Now remove the final crop and add cropping to the Resize filter (cropping takes place before the resizing when you do this). Crop away the black bars and then change the resizing filter so that it resizes to 640x272.

But....are the DVD movies only 4:3 or 16:9? I thought there were many possibiliities ad I wondered why DVD2AVI ony showed 4:3 and 16:9.

DVD VOB files are encoded only as 4:3 or 16:9. If a movie is not one of those aspect ratios black bars are added to fill the frame (or the frame is cropped). So a 2.35:1 AR movie encoded as an anamorphic 16:9 DVD will have a 720x480 frame with about 360 lines of picture and 60 lines of black, top and bottom.

Note: when using Xvid the final frame size must be a multiple of 2. And multiples of 16 work best.