Video Compression

The one line version of this section is this: when you save an animation from Cheetah 3D, the best compression option to use is either PNG (if you plan to use the animation in a video editor, such as Final Cut Pro, Premiere, After Effects, or Motion) or H264 if you want to distribute it in its current form somewhere.

If you're working in a production video environment, you might want to transcode your video into formats that work well with your digital workflow. E.g. Final Cut Pro X works well with ProRes 4444, which allows realtime preview and supports alpha channels. If you don't need transparency support, you can use the (much smaller) ProRes 422.

Finally, note that ProRes, while very high quality, is still lossily compressed. You may still prefer to keep lossless renders around if you have space.

File Size

Video compression is necessary for almost all purposes because uncompressed video files tend to be huge. (Consider that an uncompressed HD still image is 8MB, which translates to over 200MB per second at 30 fps. ProRes 422, which is lossily compressed, is up to 220MBit/s, i.e. 28MB/s — still huge, but almost 8x smaller than uncompressed.)

Big video files are not only inconvenient to work with and store, but they tend to play back poorly since they tend to overwhelm your computer’s IO bandwidth (a typical hard disk cannot read 200MB per second, nor can you send 200MB per second over gigabit ethernet).

Lossy vs. Lossless

Broadly speaking, there are two kinds of compression algorithms: lossy and lossless. Lossy algorithms attempt to improve compression ratios by selectively throwing away detail in the source image.

Lossy compression can be very efficient (e.g. typically you don’t notice any image degradation in a 3GB 1080P movie when you watch it at normal speed — even though this represents a compression ratio of over 400:1) but there are significant downsides to using lossy compression if you plan to make changes to video.

First, lossy compression throws away data based on what people tend to notice, which becomes a big problem if you make changes to the data which violate these assumptions. As a simple example — people tend not to notice detail in blue and dark areas of an image, so lossy image compression tends to “throw out” this detail. But if you perform hue or brightness adjustments to your image then missing detail that would have gone unnoticed suddenly becomes glaringly obvious.

Second, lossy compression is designed for playback, and not scrubbing or random access. When you load lossily compressed video that uses temporal compression into a video editing package it is often very unresponsive because displaying arbitrary images from a lossily compressed video clip is computationally expensive. Some lossy compression codecs (notably MJPEG) do not use temporal compression and so do not suffer from this disadvantage.

Finally, most lossy delivery codecs (such as H.264) do not support alpha channel transparency (ProRes 4444, mentioned above, is an exception). So, even if the previous disadvantages can be minimized, any video clip which uses alpha transparency needs to be saved using a lossless codec.

Production or Delivery

Most video formats are intended for either production (i.e. raw materials for producing a finished product) or delivery (i.e. the finished product ready for distribution). A simple analogy would be RAW images or negatives (production) vs. JPEG images or prints (delivery).

Typically, a production format is bigger, more complex, and less compatible with other software than a delivery format.

Alpha Channel Support

Alpha channels are the most common mechanism for representing transparency. Most image and video codecs do not support alpha channels. PNG and TIFF are two image formats with good alpha channel support.

Picking Your Target(s): Web, iPhone, iPad, etc.

The simplest way to prepare a video for distribution is to use the QuickTime Player included as part of recent versions of Mac OS X — its Export and Export for Web options will produce good results with no fuss.

Note: requires updating for Cheetah 3D 8.1.1: QuickTime Player 7 is 32-bit and can’t run on macOS 10.15 or later, which Cheetah 3D 8.1.1 requires (app Info.plist).

QuickTime Player 7 (which should still be present on your Mac) and iMovie offer more sophisticated Export options (iMovie has them in its Share menu) as do Final Cut Pro and Motion.

In general, the most compatible and highest quality format for delivering video on the web today is h264 (sometimes referred to as MP4 or MPEG4, although there is more to MP4 and MPEG4 than h264).