indessed roscivs

Frames Per Second

Today’s article is short—it’s more just background for tomorrow’s discussion of interlacing.

The basic idea is that moving pictures are made up of a lot of single, static pictures shown rapidly in succession, giving the illusion of motion. Each single image is typically called a “frame”, thus the number of images displayed in a single second is referred to as “Frames Per Second”. Movies are typically 24 frames per second, whereas standard TV (NTSC) is “29.97″, or 30 frames for every 1.001 seconds (the .001 being due to a nasty hack to implement color).

If your TV is set up for 30 frames per second, and the signal coming in is 30 frames per second, then you have no problem—the TV displays every frame. But if your TV is set up for 24 frames per second, and the signal coming in is 30—or vice versa—then you have to resort to some trickery to get the two to work properly.

For example, converting from film (24 fps) to NTSC (30 fps) requires playing some of the frames in the original extra times, sometimes resulting in jittery motion during steady camera pans. But usually interlacing is involved, too, which leads us to tomorrow’s discussion …

This entry was posted on Monday, May 21st, 2007 at 9:21 pm and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.