[MEncoder-users] frame size confusion

[Dave M G]

Mencoder list,

Forgive me if this question is very basic. I think it should be 
something that isn't so confusing, and yet, I'm confused.

As described in an earlier post, I have a Sony HD camera that records to 
an MPEG format. The camera connects by USB, and appears as a local hard 
drive, so it does not require any DV capture utilities.

Just for reference, the specific camera is the Sony DCR-SR300.

I can record in two different formats which I'll refer to as "wide 
screen" and "regular".

Here's where the confusion is. I thought "wide screen" was 720x480, and 
"regular" was "640x480". When I transfer files over to my computer, 
right click on them (I'm using Ubuntu 7.10 with Gnome Desktop) and look 
at their properties, that's exactly what they say.

However, whenever I've been using Mencoder, or my preferred GUI editor 
Kdenlive, I get all sorts of squashing and stretching of images with output.

So I took a "wide screen" video, rendered a screen shot, then opened it 
in GIMP and the frame size was 720x405 pixels. Weird.

So then I did the same with a "regular" video, and the screen shot was 
640x480 after all.

But, from looking at the video on the camera, it looks like all it does 
when recording in "regular" is trim off the sides

So I'm confused. Why does the "widescreen" report itself as 720x480 when 
it doesn't seem to be? Is the 640x480 actually that size? Am I not 
taking something into account about how aspect ratios work?

Bottom line - how can I be sure of exactly what the details of these 
files are? What their aspect ratio, pixel size, and everything else is, 
so that I know where I'm starting from?

Thank you for any advice.

-- 
Dave M G