Session D: Supporting Change in Learning and Teaching
Greenberg : A Hybrid System for Delivering Web Based Distance Learning and Teaching Material

6. Technical Issues

6.1 Storage Limitations

The most common DVD-ROM format in mass production today, DVD-9, consists of two data layers on one side of a disc, each layer holding around 4.5 GB. The S103 material requires over 13GB of data storage (text and software: 4.5GB, TV programmes in MPEG-1: 4GB, video programmes: 4.8GB). The amount of data storage required by video material depends on the compression format adopted. Opting for higher data rates during compression results in larger data files but better image quality and the MPEG-1 format (1 Mbits/sec) offers a reasonable data storage/image quality compromise. As there are no direct links from the text material to the broadcast programmes, these will be put on a separate DVD-5 disc which has one data layer.

6.2 Video Encoding

While MPEG encoding has yielded some impressive results, there is a problem in creating a format suitable for domestic DVD players and PC based software players. Most PCs with DVD-ROM drives are shipped with software DVD players and the various DVD authoring products have their own software players. Therefore, rather than relying on a wide range of DVD players on student‘s machines, we are likely to bundle our own player with the DVD-ROM based material and install it on the student‘s PC.

6.3 DVD Audio

There is some ambiguity as to the most compatible format for audio and the options include: Dolby (AC3) 5 channel, Dolby Stereo, Dolby Mono, MPEG Audio stereo, MPEG Audio mono, PCM and advanced PCM.

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