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6.2.4.2. |
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6.2.4.2. |
The QuickTime video extensions for the Macintosh operating system were the first widely available software-only video system, and this has now been widely used for several years. QuickTime is an open standard that can in principle use any compression technology, although currently it mostly uses moving JPEG (M-JPEG). QuickTime movies may be captured from an analogue source (together with its sound track) using any one of a number of low cost capture boards. The Screen Machine II produces excellent results. Video may be captured in real time if the capturing Macintosh is powerful enough (ie it needs to be a Quadra).
On low end Macs, good results may be obtained by capturing a single frame at a time, but any attempt to capture in real time will result in losing frames and thus a degradation of quality. As is always the case with software based video, delivery involves a trade-off between the power of the computer, the size of the video window, and the frame rate. On a Mac LC II it is possible to deliver about 12 frames per second in a window about one-eighth of the size of the screen. Given a powerful enough machine it is possible to deliver quarter screen at up to 30 frames per second.
In addition to QuickTime for the Macintosh, Apple have also released versions of QuickTime for Windows and Silicon Graphics workstations. QuickTime-for-Windows is not an end user product, but is a developers kit consisting of Windows DLL's that allow QuickTime movies to be played by Windows applications (the capture and editing of QuickTime files still has to be done on a Mac).
Some PC authoring systems already support QuickTime, and no doubt others will in the future as general interoperability increases. Apple has stated that Quicktime-for-Windows is not a full implementation of QuickTime, and that there will always be a lag between the two platforms in respect of this product.