> I believe DV Video does not have a pixel aspect. It's content is > either widescreen or not (16:9 / 4:3 if I am not mistaken)
All content has a pixel aspect ratio. However there may not be any way to determine what this is from the file. > > Since I didn't find any explanation on how to calculate the correct > sample_aspect, I figured it out myself. > I'm not entirely sure that it's correct, but at least it gives the > correct results. > > let's say you got a pal image (720*576) which should be displayed at > 16:9. Do not make this assumption. As it is incorrect. With the dimensions 704 x 576 is it *very* close to 4:3 or 16:9 However the same pixel aspect ratio is used for 704 x 576 as is 720 x 576, so 720 x 576 is wider than 4:3 or 16:9 > > > I do believe that there is some restriction on these values in some > codecs, so reducing this fraction to 64 / 45 is probably a good idea. 64:45 is an incorrect pixel aspect ratio. Here is my handy table which I calculated, I've included the incorrect aspect ratio as well. (taken from http://www.mir.com/DMG/aspect.html) also wikipedia has an article http://en.wikipedia.org/wiki/Pixel_aspect_ratio and more references: http://lipas.uwasa.fi/~f76998/video/conversion/ If you are converting from one format to another which both formats don't use square pixels, then use the Rec.601 pixel ratios. But if you are converting to a square pixel format (say divx) then use the true square pixels. NTSC 4:3 8:9 incorrect 10:11 Rec 601 square pixels 4320:4739 true square pixels NTSC 16:9 32:27 incorrect 40:33 Rec 601 square pixels 5760:4739 true square pixels PAL 4:3 16:15 incorrect 59:54 Rec 601 square pixels 128:117 true square pixels PAL 16:9 64:45 incorrect 118:81 Rec 601 square pixels 512:351 true square pixels I hope this clears up any confusion about Pixel Aspect ratios... Mark _______________________________________________ libav-user mailing list [email protected] https://lists.mplayerhq.hu/mailman/listinfo/libav-user
