Aspect Ratio adjusting automatically

[drunksaiyan]

Just a quick question (apologies if this isn't an Avisynth thing or should be in the Newbie forum), but I've noticed on some files that while the resolution they are made at are 720x576 for example, when played (in VLC most notably) they are automatically shifted to a 16:9 resolution, with 576 as the base dimension. This makes it larger, along the lines of 1024x576, despite the default size of 720x576.

Is this an Avisynth thing? Or something determined when an item is muxed? (I've noticed an Aspect Ratio thing in Yamb, not too sure though.)

[thetoof]

mkvmerge -- Click on the video file -- Format specific option tab -- Aspect Ration (you can choose anything you want... could even be 7,819274:1, you only have to write 7,819274 in the "aspect ratio" box
Then, on playback, it will be resized (btw, this is called "anamorphic")

[Spuds]

Its not really an Avisynth thing, it has to do with DAR (display aspect ratio) and PAR (pixel aspect ratio) and SAR (sample aspect ratio). Gspot will show you what the video has encoded into it w.r.t. PAR,DAR,SAR. Note that not all players do the correct thing with AR signaling so just because its encoded ..... Anyway go here (http://www.animemusicvideos.org/guides/avtech/aspectratios.html) if you would like some further reading on AR's.