What is Dolby Digital?

Dolby Digital, also known as AC-3, is an audio technique developed by Dolby Laboratories to compress as many as 6 channels of crystal clear digital surround sound into a single digital bitstream which reduces storage requirements.

With a maximum of 6 separate or `discrete' channels, the left, center and right channels located in front of you provide precise, clear positioning of dialogue. Two separate channels located behind you deliver immersive ambient sounds whilst the subwoofer/effects channel sends an explosive punch during action sequences. The combination of 5 discrete channels and 1 subwoofer is commonly known as the 5.1 configuration.

The delivery of spectacular audio realism at practical data compression ratios has seen Dolby Digital used extensively in in movie theaters, on LaserDiscs, and more recently, on DVD to deliver high-quality surround sound to the viewer. Media marked with the Dolby Digital logo does not automatically mean that it has surround sound or that there are 6 channels of audio encoded in it. It means that the audio information has been compressed using the Dolby Digital technique.

DVDs and PCs

The increasing number of DVD titles, coupled with the emergence of quality PC-DVD playback solutions, has made DVD playback on the PC an increasingly popular way to get entertainment and information. Compared to consumer players, PC-DVD solutions are lower priced and offer equal, if not better quality playback. PC-DVD users can also play other DVD media such as DVD-ROM, something which consumer players cannot handle. DVD-ROM will likely replace CD-ROM in the future as the medium of choice for games and applications.

What do you need to playback DVD on the PC?

To enjoy DVD on the PC, the most important component you'll need is the PC DVD-ROM drive. You will also need a DVD decoder, which can come in the form of software, like Intervideo̼ WinDVD 2000 or CyberLink̼ PowerDVD 2.55. Hardware DVD decoders are also available, such as SmartView PC-DVD Decoder.

If you choose the software option, it is important to note that it takes a lot of processing power to decode DVD Video. Therefore, you will need a very fast CPU (Pentium 300 MHz and above) to complete the task. Even then, your PC's resources will be tied up with the decoding of video and audio and you will not be able to run any other software simultaneously. This means that any game that uses Dolby Digital may suffer from performance degradation. SmartView PC-DVD Encore series does the decoding with a separate, dedicated hardware decoder; much less CPU power is needed. The picture and sound quality is also greatly improved.

Of course, a movie wouldn't be very interesting without sound, so you will need a sound card and speakers as well to complete your basic set-up. In this case, the decoder will extract the sound from the DVD, downmix it into stereo and pass it to the sound card. Usually, the decoder will also send the compressed Dolby Digital signal out its own SPDIF output (in the case of hardware decoders), or via the sound card's SPDIF output in the case of some software decoders.

SmartView Sound Live! and Dolby Digital

To get Dolby Digital surround sound in 5.1 channels on your PC, a Dolby Digital decoder is normally required. The Dolby Digital signal from the DVD decoder card is decompressed into 5.1 channels and then sent to the various speakers, giving you the full surround sound.