On Tue, 15 Feb 2005, Steven M. Schultz wrote: > Go thru the references and you'll find that NTSC full frame is 704x480 > NOT 720x480. If you really want 720x480 I'll get to that in a minute > or two...
Actually, you'll find the full frame is 710.85x486. This number is difficult for digital systems, so we round down to the nearest multiple of 16 and use 704x480 instead. > IF you really want (or need) 720x480 you have a couple choices: > > 1) Pad (as per the references above) the 704x480 scaled image with > > 2) Pretend (as I have seen in several books) that the SAR is really > 9:10 instead of 10:11. I have seen the distinction drawn between There is no need to do anything special for 720x480 instead of 704x480, you can use the same math. 1) Horizontal only scaling Output Width = Input Width * Input SAR / Output SAR Output Height = Input Height 2) Vertical only scaling Output Width = Input Width Output Height = Input Height / Input SAR * Output SAR If you are going from a non-anamorphic DVD to a computer, the input SAR is 10/11, and the output is 1/1. The input height is 480 and the input width is 704 or 720. Want to scale vertically and get 720x480? 480 / (10/11) * (1/1) = 528, use 720x528 Want to scale vertically and get 704x480? 480 / (10/11) * (1/1) = 528, use 704x528 Want to scale horizontally and get 704x480? 704 * (10/11) / (1/1) = 640, use 640x480 Want to scale horizintally and get 720x480? 720 * (10/11) / (1/1) = 654.54, use 654x480 ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
