>From: "Steven M. Schultz" <[EMAIL PROTECTED]> ... > > Downscaling feels more correct. Removing information is preferable > to synthesizing it.
(But in this case you may end up removing more information than you would have started with by taking the synthesis route.) >> may not matter much, though. In any case, you will get proper aspect ratio >> only if you scale by the correct SAR value: 10:11 in case of NTSC. So > > Ah, but if you read Martin Sitter's DVD Studio Pro book (or take a look > at books on Adobe Photoshop) it would seem that NTSC TVs use 9:10 I guess Martin Sitter read a lot of books on Photoshop, instead of reading books on video engineering. NTSC TV's use 10:11 (as referenced to the "industry standard" square pixel aspect ratio). >> 640x480 --> 704x480 or 720x540 --> 704x480, if you prefer 540. This need >> to scale in both directions is another reason to keep away from 720x540. > > But since DVDs are 720x480 there's no scaling in the horizontal > dimension - that stays at 720. Selva's point is that "720x540" is a 4:3 frame using 1:1 pixels, but, "720x480" is *not* a 4:3 frame using NTSC pixels. >> Very confusing indeed;) Take a look at Aho's page (the link above), you >> may find some logic behind all those convoluted and confusing standards. > > I've seen that - it didn't say anything about the source of my > confusion (where'd 9:10 and 720x486 come from? ;)) and Matto's > http://www.mir.com/DMG/aspect.html 9:10 probably came from reading tea leaves. The difference between 9:10 and 10:11 is 1 percent -- I doubt that anyone's TV set has its horizontal and vertical sizes adjusted to 1% precision. (I adjust the H/V size of my monitor to millimeter precision using a ruler, but I am sometimes described as "misunderstood".) > Guess I'll have to try both sizes with a DVD using overlay highlights > and see if the books are correct about a misalignment when using > 720x540 instead of 720x534 ;) Hmm... it is, of course, completely possible that the people who wrote the standard for "DVD" decided that everything was referenced to some mythical "720x534" frame size.... :^P -matt m. ------------------------------------------------------- This SF.NET email is sponsored by: eBay Great deals on office technology -- on eBay now! Click here: http://adfarm.mediaplex.com/ad/ck/711-11697-6916-5 _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
