aspect ratio question

[brianhj]

ok my original avi is 528 x 288.
ntsc dvd resolution is 720 x 480, correct?
in order to convert this avi to dvd standards, as far as AR is concerned, the picture would need to stretched to 720 width which would make the height..... 392-ish, right? (maintaining aspect ratio)
which would mean the video would need to be letterboxed.
so, 480-392=88... 88/2=44... borders 44 pixels tall on the top and bottom of picture.
....
right?
what am i missing?

[Cornucopia]

Work from the other direction...

528/288 = 1.83, ok so that's very close to 1.85 DAR (probably wasn't originated correctly)

1.85 * 288 = 532
(all assuming 1:1 PAR)
If you had a DAR of 16:9 (1.77777), your vertical rez would be ~ 300. Pretend your AVI is 532x300 (1:1 PAR, 16:9 DAR)

Now, you're going to DVD, which would have a rez of 853 x 480 were it to have a PAR of 1:1 and DAR of 16:9.
(It's not, so you should actually end up with 720x480, with PAR of .9090909 and DAR of 16:9).


Do this:
resize your video to 704x460. Don't question it, just do it!, Now, pad out your file 8 pixels of black on left, 8 on right, 10 on top and 10 on bottom.

Author your DVD as 16:9 anamorphic and you're set!

Scott

[jagabo]

FitCD

[brianhj]

Work from the other direction...

528/288 = 1.83, ok so that's very close to 1.85 DAR (probably wasn't originated correctly)

1.85 * 288 = 532
(all assuming 1:1 PAR)
If you had a DAR of 16:9 (1.77777), your vertical rez would be ~ 300. Pretend your AVI is 532x300 (1:1 PAR, 16:9 DAR)

Now, you're going to DVD, which would have a rez of 853 x 480 were it to have a PAR of 1:1 and DAR of 16:9.
(It's not, so you should actually end up with 720x480, with PAR of .9090909 and DAR of 16:9).

Thank you for the detailed reply!

I'm so confused...

Do this:
resize your video to 704x460. Don't question it, just do it!, Now, pad out your file 8 pixels of black on left, 8 on right, 10 on top and 10 on bottom.

Author your DVD as 16:9 anamorphic and you're set!

Do I tell the encoder 1:1 and then author as 16:9 or do I encode as 16:9?

[Cornucopia]

When you're encoding to MPEG2 for DVD, you should NEVER encode a PAR of 1:1. It's acceptable for generic MPEG2, but not for DVD which is a more narrowly defined subset of MPEG2.
You should encode to a resolution and to a DAR. For DVD, (NTSC) resolutions of 352x240, 352x480, 704x480 and 720x480 are acceptable, and that's all. As well, DARs of 4:3 (aka 1.3333) and 16:9 (aka 1.77777) are the ONLY 2 that are acceptable. If your material doesn't already match one of those 2 DARs (at whatever resolution or PAR), you'll need to pad/crop to get into one of them (Just like I mentioned above). This includes 1.85 and 2.35 film DARs.
So given your 528x288 source file, you should once again:
1. Resize to 704x460
2. Pad out with black to 720x480
3. Encode to MPEG2 720x480 with a DAR of 16:9
4. Author to DVD as 16:9--flagged material.

If the encoder in 3 expects or "asks" if its source file has a 1:1PAR, it doesn't. At least not at that point.

Scott

[brianhj]

If i'm padding out to 720x480 anyway... why not do it my way from the original post? Is it because i was assuminig everything was 1:1? (and it's actually more complicated than that?)

Ok say I did it my way... what would the resulting DVD turn out to look like when played on a normal 4:3 tv? (old school, not lcd or plasma )

I'm just trying to figure this stuff out

[Cornucopia]

Yes, it's because you're assuming everything is 1:1 PAR, which it isn't.

Sure, your source AVI file is probably 1:1 (most people default to that, partly because of limited understanding and need for easiness, and partly because not many players--hardware or software--support non-square pixel AR flag recognition in AVI files).
But there is NO SUCH THING as a 1:1 PAR DVD-Video (at least not one that conforms to the spec).
For NTSC, if the DAR is 4:3 (aka 1.33333) and rez is 720x480, the PAR is 0.9090909 (width/height) or 1.1 (height/width). If the DAR is 16:9 (1.77777) with the same rez, the PAR is .825 (width/height) or 1.2121212 (height/width).

Doing it your way, with a 392pixel height (prior to padding with black for letterbox), would have given you a DAR of ~2.15:1 with everything height-squashed a good deal more than it should have been.

Scott