The appearance of affordable DVD burners has given cause to celebration among the world's digital video makers – from hobbyists to professionals. The potential of DVD Video for corporate and wedding video makers is clear, but even the ability to present holiday videos in bite-sized, episodic and easily accessible chunks can't be sniffed at.
Making the right hardware and software choices isn't easy though, and there's still a long way to go before editors on a budget can 'produce DVD videos like the Hollywood pros' – a common claim on promotional bumf for authoring software. The consumer and prosumer markets are limited, but that doesn't mean there's no potential.
DVD Video
Ask most people what the biggest advantage of DVD over VHS is and they'll say picture quality. True, well-encoded DVD Video has twice the horizontal resolution of VHS, but quality only goes a short way to explaining the format's immense success. The greater appeal lies in its non-linear structure, which allows viewers to skip chapters immediately and access alternative soundtracks, commentaries and subtitles. Plus, DVD is a robust format that doesn't get chewed on player heads the way tape can, and you don't need to rewind a DVD when you've finished watching it. Also, unlike LaserDisc, DVDs are small – conveniently CD-sized – and you can fit a feature-length movie on one side.
Each side of a DVD disc can have two layers, and a single layer has a maximum capacity of 4.7GB. Dual-layered DVDs, known as
DVD-9 (single-layered discs are called DVD-5), can only be created by pressing discs in a commercial replication house. There are also double-sided DVD discs, known as DVD-10. There's currently no dual-layered recordable DVD format, but double-sided recordable DVD discs are on the horizon.
Recordable DVD is a hot issue, and a lot of money stands to be made from the licensing of the recordable media standard. DVD burning was first introduced by Pioneer with its DVD-R format. This required a very expensive SCSI burner – the DVR-S201 still sells for over $10,000. The format can't be used for making copy-protected DVD masters for replication, but it can seemingly be used to pirate copy-protected discs. As such, professional DVD drives have been kept out of the mainstream with artificially inflated prices and modest exposure.
A new variation of DVD-R was launched for the consumer market – 'General Use' DVD-R – that accompanied Pioneer's affordable EIDE-connected DVD burner, the DVR-A03. General Use discs can't be used to copy CSS-protected retail software and are therefore considered safe for the general public. With General Use DVD-R came a re-writable format, DVD-RW.
DVD-R discs have a theoretical capacity of 4.7GB, but once lead-ins and lead-outs have been added, you shouldn't plan for more than 4.3GB. Video projects burned to General Use DVD-R discs play well on many machines, but compatibility is nowhere near 100%. The newer the model, the better your chances of getting a disc to play, but DVD-R won't really be a safe bet until all the incompatible players have died and been replaced. Although 4.7GB 'Authoring' discs have the same compatibility issues, the 3.8GB disc performs slightly better. Pioneer's DVD-RW discs have generally not performed as well as write-once discs with set-top players, but they're still useful for proofing work in progress without wasting media.
Pioneer's rival in the recordable DVD war is Philips with its DVD+RW standard and, more recently, DVD+R. While DVD-R and DVD-RW are recognised by the DVD Forum, DVD+R and DVD+RW aren't, which is why they don't carry the familiar DVD logo. Pre-launch claims for DVD+RW suggested that compatibility of discs with existing set-top players was close to total. Real-world reports concluded that this wasn't the case. DVD+RW discs are far less player-friendly, having about the same compatibility rate of DVD-RW.
Philips responded with a new write-once format, called DVD+R. The same compatibility claims that were made for DVD+RW have been circulating in DVD authoring communities, but these are unverified at this stage. Philips' DVD+RW is a good format for packet-writing however, taking less time to finalise than a DVD-RW disc (as you can see in this month's Labs, page 92). It's also claimed that, unlike DVD-R, a DVD+R disc can have its table of contents changed as often as needs be before it's finalised. It's still too early to say which format is likely to become the single recordable standard, but the majority of video enthusiasts and freelance professionals seem committed to using Pioneer's General Use DVD-R.
Such fierce competition means the price of drives and media is falling daily. You can currently expect to pay around $900 for a DVD burner and as little as $12 for DVD-R discs. Be aware, however, that many cheap unbranded discs aren't recognised by set-top players, and some are even rejected by DVD burners.
The standard video format for DVD Video titles is MPEG-2. This has a generous resolution of 720 x 576 pixels for PAL and 720 x 480 for NTSC. If very high compression rates are needed, the vertical resolution may be halved, but this isn't a common practice. DVD authors can select a video data rate to suit the length of the video and the capacity of the disc, but that data rate can't exceed 9.8Mb/s.
Unlike DV, DVD-compliant MPEG-2 is composed of three types of frame. 'I' frames are complete self-contained images, while 'P' and 'B' frames are partial frames, created by analysing the extent of visual change. In this manner, only the parts of the frame that are changing are updated and the data rate can be kept low.
Supported audio formats are linear PCM audio at 48kHz or 96kHz, or Dolby's AC-3 format (with a maximum data rate of 448Kb/s). The PAL DVD Video standard also supports MPEG-2 audio, but the NTSC standard doesn't.
DVD Video supports up to eight video angles, which can be chosen by the viewer during playback. It also allows a maximum of eight audio channels, which can contain foreign language versions of the soundtrack or commentaries. Up to 32 subtitle streams can also be added to a video track. Videos can have up to 99 chapter markers, and DVD discs may carry 99 slide shows, each with a maximum of 99 images. The menus that hold all this together can be still or animated, and be made to launch Web browsers and access Websites if the disc is viewed on a PC.
These features present great possibilities to makers of wedding videos and corporate marketing folk, and I'm sure even the keen amateur would find a creative use for many of them. Unfortunately, despite healthy competition between software developers, sub-$2,000 DVD authoring tools for Windows are still extremely limited.
Media Preparation
Most DVD authoring applications come with an MPEG encoder to convert video into a DVD-compliant form. For many, having the authoring package calculate an appropriate data rate for the target MPEG stream and encode at the end of the authoring process is a convenient way of working. Small projects can enjoy low rates of video compression, so picture quality will be good no matter what encoder is used. For longer projects, higher compression levels are required, and in this situation not all MPEG encoders are the same. What's more, the search for an ideal encoder will depend on your work requirements – is speed, quality or control the most important factor for you?
MPEG encoders come in two flavours – hardware and software. Most hardware encoders are video-capture cards, sporting S-Video and composite vid