After some time of absence it is time to catch up with events here in our “Breaking the silence” column. I’d like to let everyone know that DVD has once again taken a giant step a few short weeks ago, by finally realizing the long awaited DVD-18 format, which allows up to 8-hours of entertainment on a single DVD disc!

As you are certainly aware, there are a number of different DVD specifications and formats, from DVD-Video, DVD-ROM, DVD-RAM to DVD-Audio and more. In the home video arena, we are mostly interested in the standard DVD-Video format, which comes in a variety of specifications.

DVD-5 was the first format specification and is simply a single layer, single sided disc. It was the format that was used for the earliest of releases and still is one of the most popular DVD formats around. It can hold approximately 130 minutes of video, which is sufficient for the majority of films in the market.

The introduction of DVD-10 upped the limits quite a bit. It is the single layer, double sided version of a DVD disc, which allowed publishers to put content on both sided of a DVD disc. This format can hold about 130 minutes of video on each sides of the disc. It is almost constantly used by publishers like Warner and Columbia, who put a widescreen presentation of their films on one side and a pan & scan transfer on the flip side of most of their discs.

It took some time but in late 1997 the DVD-9 process was finished and Live Entertainment’s “Terminator 2: Judgement Day” was the first release to utilize DVD-9’s superior features. DVD-9 is a dual layered, single sided disc, which can be easily recognized by its golden color as opposed to the clear silver coloration of single layered discs. With a storage capacity of almost 8 gigabytes, dual layered discs allow for up to 4hours of uninterrupted movie entertainment on a single side of a single disc. All DVD players are capable of playing these discs, although some players exhibit minor hick-ups at the layer switch points of these discs, where the laser needs to be re-focused to read from the second layer. While this brief delay may be distracting at times, this feature is not to be beaten by any other format around.  When upcoming player generations with increased read-ahead buffers come around, even this “hick up” problem should be solved.

Finally, DVD-18 is a DVD format that allows for up to 8 hours of movie playback. It is a dual layered, double-sided disc, and until very recently, no production and replication facility has been able to actually mass-produce these discs. Once again Artisan, or Live Entertainment as they were formerly called, is on the leading edge of this technology. As announced some time ago in our Hotseat interview, the company has been actively pursuing DVD-18 in order to release the TV-miniseries “The Stand” on DVD. Now, Artisan has signaled that production for this release is under way. It will still take some time to streamline the production process and get the authoring for this new format specification right, but come fall we will certainly see Artisan release the first DVD-18 disc and once again push the envelope for our favorite home video format.

When I am talking about 4 hours or 8 hours of movie playback, these numbers have to be taken carefully however. These numbers are not set in stone and depend highly on the material on the disc and the compression applied to these materials. Many people seem to misunderstand that there are a large number of variables determining the running length of each individual disc.

DVD uses compressed audio and video streams to bring movies to your screen. While the compression applied to these streams can be generally be funneled, the result is never static.
The quality of the source material is probably the single most important aspect when it comes to compressing video. If an image contains a lot of noise or film grain, it is much harder for the compression algorithm to create an appropriate compressed counterpart of the image. Scratches and other fluctuant elements found on literally every film transfer make it also very hard to create tightly compressed files that maintain all of the image’s details. Therefore, less compression is usually applied to these films or scenes, in order to maintain the overall quality. Less compression means bigger files, which in turn means that the disc can hold less playing time, of course.
Also, if you compress a scene with very little movement in each of its individual frames, DVD’s MPEG-2 compression algorithm can very easily and efficiently compress each frame, based on differences to the previous frame. The result is a very tight compressed file.
If a scene contains a lot of movement however, it is much harder for the compression algorithm to crunch the picture information down and adequately describe the image content. Unless you want to lose a lot of detail, the resulting compressed file will be substantially larger than our previous, more static, example.

Films usually consist of a rather balanced mix of both static and animated scenes, so as a rule of thumb you can usually expect to squeeze a certain length of video on a DVD disc. But don’t forget that audio tracks take up some space as well. If you have three separate 5.1 channel Dolby Digital soundtracks on a disc, this will substantially reduce the amount available for the video stream, resulting in an overall shorter playing capacity of a disc. A full-blown 6 channel DTS bitstream can take on such huge proportions that it truly overshadows the video stream.

DVD-18 is a great step, breaking the last existing barriers of the DVD technology. Although there are not very many films that require this kind of storage capacity, it is good to know that no matter what you the demand is, DVD can now live up to it.

Have a great week everyone and enjoy your movies.

 February 28, 1998

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