The 'Unofficial' iMovie FAQ

Put a movie to CD that will play in most any CD-ROM

Last edited: 27 November, 2004
Author: Daniel Slagle

How to share Movies with your Windows friends and put a movie to CD that will play in most any CD-ROM

Get your friends to load QuickTime for Windows or else you going to have to convert the file to something like an AVI or MPEG.


If you want to give them a movie on CD

  1. From QuickTime Pro Export
  2. Sorenson 3
  3. 320X240
  4. Medium Quality
  5. 15 frames per second
  6. Set key frames to 75
  7. Set the data rate to 150+ (100 to ensure that the movie will run on PCs and Macs built in the last five years)
  8. If not including QuickTime with CD, convert that file to an AVI for Windows compatibility.
  9. Burn either the AVI or MOV file to CD.


Get your friends to buy a Mac!


If you would like to include the full QuickTime installer on the CD just burn the file you download from here along with your movie on to the CD.

Max Size for Movie on CD-ROM
As explained by: Douglas Toltzman

The key to determining the final size of the movie is to set the maximum bit-rate. If you have a 34 minute movie you want to fit on a 700MB CDR, you need to divide 700MB by the number of seconds in your movie (34*60).

This calculation would look like this:

1MB = 1024KB, so 700MB=716800KB

KB/second = 716800

KB / 2040 seconds

KB/second = 351.37

A safe limit would probably be 345KB/second. Set key frames to 1 every 5 to 10 seconds. e.g. at 24fps, key frame every 120 to 240 frames. You should probably stay around 320x240 for the frame size, given the rest of these parameters.

The LONG answer:

Here are some guidelines as to what you can expect from your compression and how to take your first guess at a data-rate.

Note: The compression process won't adjust your frame size, frames-per-second, or key frame settings. It will reduce the quality of each frame and degrade the effective resolution if you don't give it enough bits to maintain decent quality.

That said, we need to first compute the uncompressed data-rate of the movie. We will do this in KB (1024 byte units) and I am going to assume you want millions of colors (3 bytes per pixel).

The calculation for 1 second of video without compression would then be;

KB/Second = (frame_width * frame_height * 3 * frames_per_second)/1024

BTW: this only accounts for the video. The uncompressed, stereo, 16-bit audio is about 100-187KB/second. You can just add 180KB to the number you got above, if you want to be very accurate. The video rate is generally so much higher, the audio can be ignored for rough calculations with high resolution video.

Lets do an example, then;
I'm going to compress a movie for CD-ROM that will be 400x300 at 24 frames/second with 16-bit 44.1Khz stereo audio.

My uncompressed video rate is:
(400 * 300 * 3 * 24)/1024 = 8437.5 KB/second
My uncompressed audio rate is:
44100*2*2/1024 = 172.26 KB/second

My total uncompressed data rate is:
8437.5 + 172.26 = ~8610 KB/second.

You can see here, that the audio didn't really add a large percentage to the total data rate.

Ok, so what does this mean to me?

Well, here we get into subjective numbers. Different types of video compress better than others. A slide show can be compressed a lot more than a video with lots of motion. Lets start with a goal of 20 to 1 compression and we'll go from there.

If I want 20 to 1 compression from 8610KB/second, I'm left with 430KB/second. 20:1 is pretty optimistic for Sorenson, but I might try this data rate to see how it comes out. For these experiments, you should have a 30 second reference movie that is representative of the movie you are going to distribute.

Once you've compressed your reference movie, keep the reference movie and annotate it as a 20:1 compression. If you think the quality is inadequate, try this again with a 10:1 compression. You must find the compression ratio that works for this material. Once you've done this, you can determine the maximum frame size or frame-rate (or both) that you can use to achieve a target data rate for your movie with predictable quality.

Let me continue with my example;

I compress with 20:1 (430KB/second) and I'm not totally satisfied. The movie is almost good enough, so I'm going to try 15:1 compression which takes me to 574KB/second. After compressing my reference movie, I find it looks very nice, overall. There is some "blockiness" in isolated areas of high motion, but I am willing to accept that to keep the movie size down.

Now that I've determined that Sorenson can give me the quality I want at 15:1, I can backtrack from my data-rate limit to get the most quality on my CD-ROM. My example movie is 15 minutes long (or 900 seconds). My CDR is 650MB (665,600KB). This means my maximum data-rate to fit the movie on the CD is 739KB/second. I'm going with 720KB/second to be safe. Now, I can multiply 720KB by 15 to get the uncompressed rate of 10800KB/second. For my purposes, I think I'm going to jump to 29.97 (30) frames-per-second and see where that puts me;
(400*300*3*30)/1024=10546.875 KB/second

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