[SOLVED] Maintaining proportions: gimp - Cinelerra ?

[jdetwile]

Being new to video-processing in Linux (Cinelerra, ffmpeg, Kaffeine, xine, Fedora Cool, I'm struggling with images appearing 'squeezed' in horizontal direction.

Here's a typical use-case:

1. Use gimp to draw a circle (truly round) on a 720x480 canvas, and save as jpeg. Load this file into Cinelerra (project parameters are NTSC preset). The circle is 'squeezed' - about 25% taller than its width.

2. Render a 10-sec NTSC (720x480) video of this circle (say, as ogg). Play the ogg in xine and the circle is squeezed.

3. Use ffmpeg to recode the ogg file into wmv, specifying -s 720x480 (or omit). Play the wmv and the circle is now round.

4. Run the wmv though ffmpeg (-s 720x480) into m2v, and the circle is squeezed again. (I don't see any effect of specifying -aspect, either.)

What's going on? And how do I keep my videos proportioned correctly?
Any suggestions? (FWIW: My monitor is a 1440x900 flat panel, running Gnome on fc8)

Thanks!

[GMaq]

Hello.

What happens if you import the image file into KDenlive or Kino (not sure if Kino does images) and export it as RawDV, then Import and render in Cinelerra.

I find the only Player that seems to play aspect ratio accurately without tweaking is Totem-xine, Perhaps GXine would as well since they share libxine.

[Steve Stepoway]

Welcome to the wonderful world of pixel aspect ratios. Pixels on a computer are square; a 1:1 aspect ratio. If you take a ruler and measure your flat panel, you'll find that the measurments have the same ratio as 1440:900.

But (NTSC/ATSC) video has a different pixel aspect ratio. A 720x480 video frame covers the same real-estate that's covered by a 640x480 image on a computer screen. Do the math: 720:480 is 1.5:1, while 640:480 is 1.33:1. Your image from GIMP assumes square pixels. When converted to a video frame and played, it gets a slight anamorphic squeeze, which makes everything tall and skinny.

Steve