Frame size and display aspect ratio

[JonH]

Someone using Final Cut Pro asked me to create a DVD for them. I told them to give me an MPEG2 file using a frame rate of 720 X 480 and a 4:3 aspect ratio (among other things). They can't seem to do it. When they set the frame rate to 720 X 480 the aspect ratio automatically changes to 3:2. When they change the aspect ratio to 4:3, the frame rate automatically changes to 640 X 480. Any suggestions? This is kind of like the blind leading the blind.
Thanks.
Jon

Actually, he was looking at exporting a Quick Time file rather than an MPEG2. So it may not be an issue. Sorry.

[Dr Mordrid]

The actual aspect ratio of NTSC 720x480 video frames is 3:2, however we usually call them 4:3 because that is the aspect ratio of the TV's we watch them on.

Some software will use the latter and some the former.

The video outside the displays 4:3 frame is what lies in the overscan region.

This site has a list of the various video frame sizes, their actual aspect ratios and uses;

http://www.finearts.uvic.ca/sim/help_docs/tutorials/vid_tutorial/video.html

Dr. Mordrid

[Hulk]

In addition to overscan, 720x480 displays 4:3 on a television because televisions use non-square pixels, pixel aspect ratio for 720x480 4:3 on a TV is 1:0.909.

In order for 720x480 to appear 4:3 on a square pixeled computer screen the 720 pixels must be remapped on the fly to 640 pixels.

- Mark

[JonH]

Thanks, guys. I sure have a lot to learn.