Various audio track formats on 35 mm film. L to R: Sony Dynamic Digital Sound (SDDS, a competing system); Dolby Digital (between the sprocket holes); analog Optical; DTS time code. Look very closely and you will see the Dolby "Double-D" logo in the middle of the Dolby Digital code pattern.
Dolby Digital SR-D cinema soundtracks are optically recorded on a 35 mm release print using sequential data blocks placed between every perforation hole on the sound track side of the film. A CCD scanner in the projector picks up a scanned video image of this area, and a processor correlates the image area and extracts the digital data as an AC-3 bitstream. These data are finally decoded into a 5.1 channel audio source.
Dolby Digital audio is also used on DVD-Video and other purely digital media, like home cinema. In this format, the AC-3 bitstream is interleaved with the video and control bitstreams.
The system is used in many bandwidth-limited applications other than DVD-Video, such as digital TV. The AC-3 standard allows a maximum coded bit rate of 640 kbit/s. 35 mm film prints use a fixed rate of 320 kbit/s. HD DVD and DVD-Video discs are limited to 448 kbit/s, although many players can successfully play higher-rate bitstreams (which are non-compliant with the DVD specification). ATSC and Digital cable standards limit AC-3 to 448 kbit/s. Blu-ray Disc, the Sony PlayStation 3 and the Microsoft Xbox game console can output an AC-3 signal at a full 640 kbit/s. Some Sony PlayStation 2 console games are also capable to output AC-3 standard audio as well.
Dolby is also part of a group of organizations involved in the development of AAC (Advanced Audio Coding), part of MPEG specifications, and considered the successor to MP3. AAC outperforms AC-3 at any bitrate, but is more complex.
Dolby Digital Plus (DD-Plus) is supported in HD DVD, as a mandatory codec, and in Blu-ray Disc, as an optional codec. Recently the Tiger Woods PGA Tour 09,and Tiger Woods PGA Tour 10 for the Wii Video Game Console use Dolby Digital.But Dobly Digital product for the Wii console are rare.The Wii [game console]] mostly uses Dolby Pro Logic II,and is compatible with Dolby Pro Logic IIx,but Tiger Woods PGA Tour 09,and 10' is Dolby Digital compatible.
