Resizing anamorphic DVDs?

[lichtgestalt]

Hey there!

Short question: If I plan to rip an anamorphic DVD to SVCD, should I resize the ripped AVI before the MP2 encoding?

Or put another way: as the 448 pixel wide frames are streched anyway (factor 1.5) for a normal 4:3 ratio and stretched even further to widescreen, 16:9, would it make sense to letterbox it first?

I'm not quite sure what I'm aiming at really, but I have the feeling that anamorph material sucks up a lot of bandwith as there are no black letterbox borders at the top and bottom. Is there a quality gain worth it?

What do you think?
Thanks very much

lichtgestalt

[Truman]

First off SVCD standard and most DVD players support DAR 4:3 only.
If you have a widescreen TV, you can encode to 480x576 DAR 16:9, but probably it will be displayed stretched on your neighbor's 4:3 TV.

Of course you have to resize and letterbox before encoding, no matter whether you use a Vdub, Avisynth or TMPG resize filter.

Resizing to 480x576 anamorphic is not a quality gain unless you increase the bitrate drasticly.
An example: Your source is DVD 720x576, DAR 16:9, anamorphic, not letterboxed.
1. You can resize to 448x538 and add the borders left 16, top 19, right 16, buttom 19. -->XSVCD DAR 16:9. In this case you have to encode 952 macroblocks resp. 5712 blocks (YUV 4:2:0)
2. You can resize to 448x404 and add the borders left 16, top 86, right 16, buttom 86. -->SVCD DAR 4:3. In this case you have to encode 728 macroblocks resp. 4368 blocks (YUV 4:2:0)
As you can see in the 1st example you have to encode 30 % more pixels / blocks. So you have to use a 30 % higher bitrate. If this is no problem for you, do it, because you might end with a higher quality due to the higher resolution. If you want to fit more on one CD, resize to 4:3 and use the zoom function of the widescreen TV.
Personally I don't believe, that the 16:9 example will look much better than the 4:3 example, but I can not proof it.

[lichtgestalt]

Thanks Mr. Truman!
This is exactly what I wanted to hear and what I suspected from the start. The thing I wasn't sure about was the exact dimensions, 448x538 for 16:9 and 448x404 for 4:3. I'm still not sure how one arrives at those, but I gladly take that for further experimentation.

Thanks again!

lichtgestalt

[lichtgestalt]

Oh, we're talking PAL, right?

lichtgestalt

[Mr Walker]

Hello.
Truman, can you explain to me wyh you want to add borders to the right and left side?? And as far as i know an "anamorphic" (DAR16:9) will look better than a zoomed 4:3 letterbox movie, but that's only my opinion.

Maybe a bit of topic but anyway, if you play an anamorphic dvd on a 4:3 tv the picture get less horizontal resolution, as the player remove every 3:rd or 4:th line of the picture and then add the black "letterboxed" borders. This according to www.thedigitalbits.com

So if you have an widescreen tv, anamorphic would be the best way to go.

[Truman]

lichtgestalt, yes I'm talking about PAL and I use FitCD to do that calculations.
Mr Walker, I add black borders arround the image, not only left and right, because these parts of the image are not visible anyway (TV overscan). Why should I waste bits? Yes, in theory a 16:9 anamorphic XSVCD must look better. Good, that you can confirm that. But only if you increase the bitrate.

[Pere]

Truman, why waste bits encoding the black borders?? Isn't it better to use those bits for something more useful, like the image itself?

[Truman]

you are kidding...

[Pere]

No, man, I don't know how MPEG2 encoding works, but I guess it will spend some bits encoding those black borders... just as MP3 spends some bits encoding silence passages... am I wrong?

[Mr Walker]

Ok Overscan, thanx Truman. But how can you be sure what numbers. Every Tv is a little different, and it a shame if a movie looks good on one set but a "black line at the right" on a another just cause that tv isn't trimmed as the first one.

Hope you get the point.

[Truman]

Yes, every TV is different. You have to check out the overscan area of your TV by yourself. You may download a sample SVCD image to test it. (Delete the .doc extension and extract)
My TV displays only 432 of 480 pixels (horizontal resolution), 448 is a good rule of thumb.