Aspect ratio question

[bananix]

source video in this example is dvd of resolution 720x480 (aspect ratio 1.5) NTSC interlaced

if i make xvid of it with resolution 640x480 (aspect ratio 1.333) this means the video is shrinked in one dimension more than other so it loses quality to my understanding when i play it with aspect ratio 1.5 on pc monitor so it is normal (unless you crop the movie but i don't want to do that). would this method be best if watched from tv or something instead of pc monitor?

if i add black to top and bottom of the source to make it resolution 720x540 (aspect ratio 1.333) so then i can convert it to xvid of same resolution and aspect ratio so then no resize occurs. would this method be good for watching on some source?

if i make 720x480 xvid from it so the aspect ratio is the same and no resize occurs so i belive it would be best if i one wants to watch it from pc monitor am i correct? and would this be good for watching from tv or some other?

or is some other aspect ratio than 1.333 useful for some type of displays?

[guns1inger]

Don't forget that your DV avi will have a non-square pixel aspect ratio. When saved to 640 x 480 for xvid it will have a 1:1 pixel aspect ratio, which should compensate for the resizing. 720 x 480 is in fact 1.33 in DVD speak (NTSC, of course)

[manono]

You can resize it to either 640x480, or to 720x540 (but without adding black bars). GKnot will allow you to do either, although you'll have to change the default H and W-Moduls to do it at 720x540. As guns1inger mentioned, the pixels in the 720x480 DVD aren't square, and upon playback, the DVD gets resized by the player to 640x480, at which point they become square pixels. So no, the resizing by itself doesn't cause much quality degradation. The reencoding will.

You can always add black to the top and bottom (or the sides) when using GKnot by editing the .avs and adding the AddBorders command to the AviSynth script. In this case you don't want to do it.

You can also keep it at 720x480, make the XviD, and have your player resize it by 4:3. If playing from the computer this is an easy and good solution. This won't work on a standalone to a TV though.

[junkmalle]

Xvid has a display aspect ratio setting. So you can encode at 720x480 and have it displayed as a 4:3 picture on playback. Stand alone players may not pay any attention to the setting though. If you've already encoded you can use MPEG4Modifier to change the display aspect ratio.