An animation showing how 24p Standard mode works.

Note: If you cannot see the video, install Macromedia Flash Player 8 and return to this page.

I remember when I first read about 24p video three years ago and seeing a lot of diagrams that explained the cadence, or pull down pattern associated with it. I guess after seeing these, I wanted to crack open After Effects and do an animated diagram explaining the process. Well I've been sitting around bored the past couple of weeks and decided to make an attempt. I'd like to add narration, but my voice is horrible.

Here’s my brief textual explanation to go along with the diagram:

• The recorded material originates as 24 progressive frames a second. In this example there are four frames, A, B, C, and D.
• The 24p standard mode splits these four progressive frames after capture into five interlaced frames using a 2:3 pulldown pattern. The four frames are now five and are distributed as such: AA BB BC CD DD. The footage is now running at 29.97 interlaced frames a second.
• The integrity of the original C frame is sacrificed to create the two interlaced "jitter" frames: BC and CD.
• To reconstruct the original four frames, the AA, BB, and DD frames are kept, but the BC and CD frames are decompressed and combined to reconstruct the original C frame, which is compressed again.

The Bottom Line

While the standard mode offers compatibility with NTSC video, the C frame suffers a compression hit because it needs to be generated from two video frames. The 24p advanced mode, by contrast, sacrifices compatibility with NTSC video for frame integrity.

This entry was posted on Friday, December 9th, 2005 at 11:31 pm and is filed under Filmmaking, Flash, Producing 24p Video. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.