Microsoft reveals plans for DVD-ROM and DirectShow

Emedia Professional, April, 1998 by Kilroy Hughes

Microsoft Corporation has plans for promoting and enabling the large-scale launch of DVD-ROM in 1998, says Peter Biddle, the company's DVD Evangelist. A key element of Microsoft's strategy is DirectShow, a set of Application Interfaces (APIs) that allows title vendors to play back streamed audio and video that can be written in a variety of formats ranging from MPEG-1 to AVIs to DVD-Video. Because it's an API, DirectShow includes an abstraction layer from the hardware that enables a title vendor to write a DVD title without worrying about the kind of computer hardware that will be running underneath it.

DirectShow, the successor to ActiveMovie, was released in late 1997, and is downloadable from the Web at http://www. microsoft.com/directx/resources/dx5mediasdk.htm. The downloaded version includes the whole DirectX media 5.1 software developer kit (SDK), which incorporates redistributable runtimes, documentation, and sample applications.

DirectShow will run on Windows 95, Windows 98, and Windows NT 5.0 Workstation. Windows 98 is scheduled to ship during the first half of 1998 and will include DirectShow in the standard configuration.

Biddle says DVD's capacity is an obvious advantage, but that's just the starting point. "DirectShow lets you make some baseline assumptions about DVD platforms; for example, they will be able to decode and render a 9.8MB/sec MPEG-2 stream with a concurrent 5.1 channel AC-3 audio stream at a pretty good quality level. We are shooting for DVD-Video player-quality and we are starting to see it. In the past, with CD and something like MPEG-1, there were different implementations and performance levels so a user couldn't be sure if a disc was going to work well or even work at all. The goal with DirectShow is that a title vendor can test for DirectShow compliance, and the user can plug in the disc and have it work `automatically.'"

Player compatibility is a function of how the video is mastered, he explains. There are chiefly two ways of storing MPEG video on a DVD. One is in compliance with the DVD-Video 1.0 specification that defines .VOB (Video Objects) with corresponding .IFOs. By writing a disc using .VOB files for MPEG-2, Biddle says, "you can play it on a DVD-Video player, you can play it the exact same way on a PC, and you can also add DirectShow and DirectX programming and cool stuff to create a much richer playback experience on the PC," says Biddle. The PC can combine entertainment-quality audio and video with interactive random access, 3D graphics overlays, Internet connectivity, and other computer capabilities.

Revealing an important new option being added to DirectShow, Biddle says: "The other video format is standard MPEG-2 files, and we're working on support for that, which will be ready for release soon." This format won't play on DVD-Video players, but it doesn't require a complex authoring process. It makes it easy for developers and PC users to put an MPEG file straight from an encoder on their computers, or a DVD-ROM or DVD-RAM disc, and play it with simple DirectShow commands.

"When you go into a store today and buy a DVD," says Biddle, "there's a 99.9-percent chance that it won't have MCI--an alternative API--or DirectShow on it because it's going to be a DVD-Video title. There are approximately 500 of those titles that are currently available or about to be released. Of the DVD-ROM titles that you can buy retail, people count anywhere from a couple to about 30, depending on your criteria; I've personally only found less than a half-dozen. Of those, some are MCI, some are QuickTime, some are based on ActiveMovie 1.0, and some are something completely different and may not have any video assets on them at all. This is really the beginning of the market, and our goal is to build the DVD-ROM market based on DirectShow starting now."

Biddle has high expectations for the DVD-ROM market, predicting that 15 million DVD-ROM drives will be sold in 1998, and 50 million in 1999. "By the year 2000, it will be difficult to buy a system with a CD-ROM drive at all," he says. The cost of DVD-ROM is dropping through the floor, Biddle explains, and DVD decoder cards are becoming very competitive. Hybrid software decoding is looking viable on faster processors, and the drive prices have fallen so fast at the OEM level that they are competitive with today's high-end CD-ROM drives. A manufacturer or OEM, therefore, is virtually forced to switch to DVD-ROM to stay competitive. There's no reason not to. DVD-ROM drives are good CD-ROM drives as well, and the new generation reads CD-R, CD-RW, and in the future DVD-RAM, as well as DVD-ROM and DVD-Video. "With 73 million CD-ROMs sold last year, some simple arithmetic, and some manufacturers' production plans, you can get a solid idea of how many DVD-ROM drives will sell this year," Biddle says.

Another factor in making DVD-ROM happen is the improvements in decoders, in the form of both silicon parts and software decoding. Microsoft has been supporting MPEG motion compensation in video display chips as a way to do high-quality MPEG decoding that only requires a small percentage of additional gates in the display chips, but handles approximately 30 percent of the MPEG processing load and reduces the load on the data bus. Motion compensation support will be included in DirectX 6.0. With ever-faster CPUs and software-decoding advances, MPEG-2 and digital multichannel sound decoding will become a no-cost standard feature of new PCs over time. DSP and dedicated silicon makers are also designing products that produce good DVD results using different engineering approaches and deliver low system price points.