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Yale C/AIM Web Style Guide

Contents

Multimedia

Introduction

Design and AV elements

Digital Video

Digital Audio

GIF Animation

QuickTime is the format for video and sound files that we have used in our web projects. It works on both Windows and Macintosh computers without much custom configuration. The latest plug-in for QuickTime is built into Netscape 3.0, so users are not required to do any special installations.

Fast-starting video
The most current versions of the QuickTime plug-in and system software have a feature called fast start. Movies can be saved in a special format that puts all the critical file information at the start of the file data structure. This means that as soon as this information reaches the client machine, the movie can be set to play users do not have to wait until the movie is fully downloaded before clicking on the play button. Depending on network speed, a fast start QuickTime file can be played almost immediately after the page is loaded. If the "autoplay" option is set to true in the movie's HTML tag, the movie will begin playing automatically as soon as the QuickTime plug-in estimates it will be able to play the entire movie without waiting for additional data. As long as the user's connection is faster than the movie's data rate, the movie will play from start to finish without pause.
The implication of fast-start video is that duration is no longer an overriding concern for audio and video site content. At one level, it no longer matters if your video is one minute or 10, because with fast start each of these durations look essentially the same. As long as the user's connection and the movie's data rate are within the same range, your one minute movie can start playing at the same time as your 10 minute movie.

Example of video with fast start

File size is, of course, still a consideration. A 6MB movie file needs to be kept somewhere on the client machine. Some machines will crash if asked to hang onto large movie files. Assess your audience their network access, their processing power and memory configuration and plan accordingly. For example, if you have 10 minutes of video that you want to put on the web for low-end machines, chop it up into smaller chunks to make sure your audience can access it.

Data rate limits
Set the data rate of your movies slightly lower than the throughput of your user's connection is you want them to be able to watch your movies in real time. For a 28.8 modem that means a data rate somewhere around two KBps, for ISDN around five KBps, and for T1 lines from five to 40 KBps. To deliver true video at these data rates the compromises are great. The image size must be small, the frame rate low, and the sound compressed. As a result of compression the image quality will be less than optimal. Nonetheless, there is still interesting video and sound that can delivered using the web.

Creative solutions
If you are creating content for a web site, tailor your multimedia elements for web delivery. Think of creative solutions that may be more modest but will be viewable by your target audience. For example, instead of using true full-motion digital video and audio that will require so much compression and size reduction as to render it useless, use audio and a sequence of still images to add multimedia to your site. Say, for example, you want to use video to show how to cook lasagna. Instead of using video, take a bunch of still images and pair them with a good-quality narration of the recipe.
If you must use true video in your site, be sure to shoot footage that will handle the compression and size reduction required for delivery on the web. Keep away from wide shots; shoot at medium or close range so that the detail of the image will be distinguishable at small sizes. The low frame rates and small viewing size required for web video will not effectively display motion, so don't shoot video that includes much action. The best source video for the web is close-up shots of talking heads.

Pay attention to source
It is especially important that web multimedia be created from excellent source. The processing that must be applied to A/V elements in order to attain web resolution will only emphasize any flaws in your original source. If you begin with bad audio and then reduce its sample rate and depth, and then add compression to further reduce the data rate, any flaws present in the original source material will be exaggerated.

References

Rainer Maria Rilke - 3 Gedichte
Copyright 1997 P. Lynch and S. Horton,
   all rights reserved. Yale University   Revised January 1997.