My setup is that I have a computer with a standard 4:3 monitor, but I output video to my widescreen TV set through an s-video cable. Since I can only run in 4:3 resolutions (TV runs in maximum 1024x768), video does not look right on my TV when it is in it's native 16:9 mode, because the video is formatted like its being displayed on a 4:3 screen.
To currently get VLC to display videos with an aspect ratio of 16:9 correctly on my TV in fullscreen, I have to set the "source aspect ratio" setting in VLC to 4:3. However, when I then play a video that is not exactly 16:9, say 2.35:1 or 4:3 or 1.66:1 or whatever, it looks wrong.
A monitor aspect ratio setting would get the video to display correctly regardsless of what the video's source aspect ratio is, as long as that one is set correctly, of course.
Basically, it would just instruct the player that "even tho this monitor is running at a 4:3 resolution, the monitor's screen is in a different format, (meaning the pixels arent square), and the image should be stretched or squeezed accordingly to be presented correctly on the monitor.
mplayer and winamp, like mentioned, does this perfectly, when I have set the monitor's aspect ratio to 16:9, 16:9 videos are displayed full-screen, and 4:3 videos are boxed correctly with black bars on both sides of the image. Of course, they dont look right on my main computer monitor, but thats not where I am watching the video anyway.
I dont think it should be extremely hard to implement, and it would be a very cool feature to have, constantly having to change the aspect ratio manually is what keeps me from using VLC as my main video player.
