Apple QuickTime VR - Manual (Page 94)

Source material
Compression methods are optimized for specific types of source material. Video
compression is a good choice when the source material is video. If your source material is
computer-generated animation, consider using Animation or Graphics compression. Photo
JPEG compression works well with any type of source material, but is best for photographic
stills, video, and computer-generated images that do not have sharp edges.
Image quality
Except for Animation at 100 percent quality, all other compression methods provided in
QuickTime VR Authoring Studio will introduce some distortion into the image. If you are
creating a panorama or object that the user can zoom in on, choose a compression method
that preserves enough image quality to allow the user to zoom in and still see detail. You may
want to experiment with different quality levels to see how a level affects the image.
File size
Some compression methods have a higher compression ratio than others for a given image
quality. Although compression reduces file size, you should consider other ways to reduce
file size if size is a concern. If your QTVR media will be viewed over the Internet, you may
want to reduce the resolution of the images in addition to compressing the file.
Compression and decompression time
A compression method that takes the same amount of time to compress an image as it does
to decompress an image is referred to as a
symmetrical codec. When the compression and
decompression times are different, the method is called an asymmetrical codec. Some
methods that have fast decompression, such as Cinepak, take a long time to compress.
Cinepak has a 192 to 1 compression/decompression ratio.
You may want to choose a compression method with a fast compression time (but lower-quality
results) when you are previewing a panorama or object movie. Later, when you make the
final product, you can use a slower compression method that provides higher-quality results.
Comparing compression methods
The best way to assess the quality of a compression scheme for a specific file is to establish a
basis for comparison by saving the file at the best quality level. Then compress and save the
file at the next best quality level and compare it with the previous quality level. Continue
compressing, saving, and comparing until you have reached the minimum level of acceptable
quality for your project. Repeat this process for each compression method.
94 Appendix A