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Everything You Wanted to Know About Blu-ray Audio
Everything You Wanted to Know About Blu-ray Audio*
* but were afraid to hear
The Blu-ray disc format is mostly considered a visual medium. However, sound contributes substantially to the overall experience. Although Blu-ray discs look physically like DVDs, there are many differences including many differences in the audio. This white paper discusses those differences and the design issues surrounding the development of audio subsystems for Blu-ray disc players and related equipment.
Introduction to Blu-ray
The Blu-ray disc format is mostly considered a visual medium. However, sound contributes substantially to the overall experience. Although Blu-ray discs look physically like DVDs, there are many differences including many differences in the audio. This white paper discusses those differences and the design issues surrounding the development of audio subsystems for Blu-ray disc players and related equipment.
Physically, Blu-ray discs look a lot like CDs and DVDs. In fact, they're the same size: 12 centimeters for the standard Blu-ray disc and 8 centimeters for the mini-sized disc. However, Blu-ray discs have much higher storage capacities: 25-50 Gigabytes for the standard disc and roughly 8 to 16 Gigabytes for the mini-size disc. You can get a lot of audio and video on one of these discs.
The higher storage capacity results from using a blue (actually violet) laser with a much shorter wavelength than the lasers used for CDs and DVDs. The first Blu-ray players shipped in 2006, a little more than two years ago, and there are more than 1000 titles now available for Blu-ray worldwide. The release of titles may have been slowed by the battle between Blu-ray and HD DVD, but that battle's over and Blu-ray won.
Figure 1 shows what's happening to the sound inside of the Blu-ray player. Three sound channels (primary, secondary, and PCM) are mixed and then re-encoded if needed. Note that there's sample-rate conversion on the secondary and PCM audio channels before mixing-if needed-to match the data rate of the primary audio channel.
