Autodesk 64006-051108-9001 User Guide - Page 117

QuickTime 109 Note: Only H.263 and the Developer Edition of the Sorenson Video codec support this streaming option. H.263 calls this option Cycle Intra Macroblocks, and it is available through its Options dialog in the Encode tab. Lower refresh values result in shorter delays between when the viewer starts to see the image and when the image is fully drawn. However, shorter refresh values generally produce lower overall image quality because more refresh data must be included in the stream. Generally, you should always use the Force Block Refresh option, especially on content that mixes high-action and static material. Since high-action content automatically refreshes, there is no wasted bandwidth on block refreshing. Static content, such as interviews or "talking head" videos, benefits most from a block refresh because parts of the image may not change for a long period of time. A value of 2-5 seconds is often a good starting point with static material. We suggest you experiment to determine the optimal settings for your material and personal preferences. Note: Force Block Refresh should never be used with local or progressive-download movies because it wastes bandwidth. Alternates Alternate movies are primarily used to optimize the viewing experience for a wide range of viewers. Alternates work with both progressive-streaming and realtime-streaming QuickTime, as well as on the desktop with CD-ROM and DVD-ROM projects. With alternates, you can create multiple versions of a movie and set criteria for which version is played. For example, you might make a movie that has a 56k modem version, an ISDN version and a T1 version. Depending on the viewer's connection speed, they are automatically shown the version of the movie with the most appropriate data rate for their connection. This enables you to present high-quality versions of movies to viewers with high-speed connections while providing modem users with an acceptable experience at the same time. Fallbacks A fallback is the alternate movie or image displayed by the QuickTime Plug-in if it is not capable of displaying any versions of the movie. Alternates and Streaming QuickTime enables you to intermix realtime streaming and progressive-streaming alternates within the same alternate group to provide the optimal experience for a range of viewers. Often, it works well to make the modem alternates of a progressive-streaming movie and the higher-bandwidth alternates (ISDN and above) realtime streaming.