Back to school--frame rate education

Question

Hello there,
Would someone explain the difference in frame rate output when exporting a project from iMovie 11?
I see the choices for 30, 24, and 60 and one of my camcorders can record at 60fps but what are the differences and is there a quality benefit to one over the other?
thanks
Marc

Answer 1

First of all, you will typically see frame rates of 24, 25, 50 and 60. This is partly related to the TV video standards in North America vs. Europe and elsewhere. North America uses 30 and 60 frames as the standards.
They frame rates you see may be follwed with the "i" or "p" designations. "i" stands for interlace and "p" for progressive. Interlace "paints" the image on the display or screen on evey other line and alternates every other frame. For example, 60i paints the lines 60 times per second, but each frame is composed of bands that are only every other line. The image is "striped", if you will. The eye does not notice, because it happens so fast - 60 times a second. On the otherhand, 60p paints the full image 60 times per second. As you can imagine, the more lines of information and the higher the frame rate, the more "data information" that must be processed and displayed in a given amount of time. With so much date to process, 60p video taxes Mac hardware to the max. But 60p is worth it, if you can get it to play. The 60p image is so much more life-like.
HD Camcorders sold the last year or so typically record 1920 x 1080 at 30p or 60i. That is 30 frames progressive or 60 frames interlace. Many feel the 30p views better than 60i on an HDTV. Several camcorders in the $800-1000 dollar range sold today and even some less expensive camcorders record at 60p. This is a huge step up in quality - when viewed on an HDTV capable of displaying the video - and most are these days.
As far as real world image quality, when I play 1920 x 1080 HD video at 60p directly from my camcorder to my HDTV, the image quality is superb. Any action or anything moving on screen is displayed clearly without the slightest blur or streaks. Unfortunately, my 2007 vintage macs cannot keep up with this level of video quality. When I upload video from my camcorder to my Mac and try to play 1920 x 1080 60p HD content, the video stutters and freezes. I must convert my camcorder's video content to a lower frame rate such as 30p to make it playable on my Mac. I use free programs such as Handbrake to convert, but the conversion to 30p degrades image quality noticeably. The processor in my camcorder is optimized for high quality 60p video and outperforms my Mac by leaps and bounds. However, it is impractical to keep all my videos on my camcorder.
In the last couple of months, new Macs with i7 Quad Core processors and separate, dedicated graphics processors have caught up with today's camcorders and can now play and edit state of the art home video content.
Bottom line on frame rates. Record, edit and play at as high a frame rate as your equipment allows. This is especially important in recording anything with a lot of action, like sports. Given the choice between i and p, choose the p or progressive settings when recording. To future proof, my recorded video, I like to record at 60p and then convert to 30p. My camcorder would let me record at 30p or 60i (which would save me a time consuming conversion step), but instead, I go ahead and use 60p to preserve my options in the future. I save the 60p files and when I upgrade my Mac some day, I will be able to play the 60p video and enjoy the higher quality it affords.