On Wed, 11 Jun 2003, Steven M. Schultz wrote: > Hi - > > > From: Selva Nair <[EMAIL PROTECTED]> > > The general advice is to avoid vertical scaling mainly because vertical > > scalers should be interlacing-aware -- also for interlaced frames the > > and y4mscaler is, I believe, interlacing aware ;) > > Downscaling feels more correct. Removing information is preferable > to synthesizing it. > > > 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 wont touch those books.. > pixels and there are a couple NTSC frame sizes to contend with. The > use of 720x534 when designing menus and overlays is mentioned several > times with a note that 720x540 is not correct unless you're going to > D1 NTSC (720x486). > > > 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. Not if you want correct aspect ratios. Well, when it comes to aspect ratios, there is a lot of misinformation out there, hard to find who is right. As Matto suggested, simply use y4mscaler -O preset=DVD and that will take care of all necessary padding and scaling. > > > 720x534 makes no sense to me. Apparently, the popularity of 720x540 is > > because it appears related to both PAL and NTSC by a vertical scaling > > factor -- scale to 720x480 in one case and 720x576 in the other. But that > > It's a bit more complicated than that I think. > > .9 * 534 = 480.6 while 540*.9 = 486 I have seen such arguments elsewhere. The 9/10 ratio, I think, has originated from the misconception that 720x486 is 4:3. Selva ------------------------------------------------------- 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
