What does 720x480 widescreen translate best down to, - 640x360 or 854x480 ?

[Bansaw]

I have a video file 720x576 pal widescreen.
I need to get that into an mp4 square pixel format. Should I go with the 854x576 frame size, or 640x360?
640x360 involces a resize and therefore a potential minor loss in quality right?

[davexnet]

Those two ratios are not even the same. They could be anamorphic and display correctly, but then they're not square pixels.

[hello_hello]

Technically, the best "resize to square pixels" method doesn't adjust the height, only stretching the width to the correct aspect ratio. For a PAL 16:9 DVD without cropping, that'd mean 1024x576 (1024 / 576 = 1.7777777).
If, for example, you cropped 8 pixels of black from both top and bottom before encoding, then it'd be 1024x560.
The NTSC equivalents would be 854x480 without cropping or 854x464 with the same 8 pixel cropping top and bottom.
Calculating the width gets a bit trickier if you crop from the sides when the source is anamorphic, but most GUIs will do it for you.

Having said that, I've found you can generally resize down a little without any ill effects and it can help reduce the file size. I use 960x540 quite a bit for 16:9 PAL resizing (and 832x468 for NTSC as it's exactly 16:9), but you can use any 16:9 dimensions you like. Obviously though, the more you resize down the more likely you are to lose fine picture detail.

Have a play with the attached calculator. It's an exe but it's safe. As a general rule, you'd keep the "use ITU-R DAR coeff" option checked for resizing 4:3 DVDs, and uncheck it for 16:9 DVDs.
The ITU-R DAR coefficients resize the picture slightly wider than 4:3 or 16:9. In my experience 4:3 DVDs generally use the ITU resizing while 16:9 DVDs generally don't.