[MPlayer-users] Question about aspect ratios

[daniel carter]

I'm a bit confused about aspect ratios and wondering if anyone can
enlighten me?
What is the purpose of specifing aspect ratios?

First the aspect of the video source.  Suppose i have a video that is
576x240. well the aspect ratio is 2.4, why would i want to tell mplayer
that the aspect ratio is 2.4?

Why would a video be encoded at an aspect ratio that is not its true
aspect ratio, surely stretching it in software after decoding would give
worse quality than just encoding it at the correct ratio?

Secondly, specifing the monitor aspect. Well if my monitor is at 800x600
then the aspect is 1.333333333... Why would i want or need to tell
mplayer that?

TIA,
dan.