This is the 5.1 Surround Audio version of Ghostwalk .
The pack includes the following formats :
1/ Dolby Digital (.AC3)
2/ Dolby Digital Plus (.MP4)
5.1 discrete channels of High-Fidelity Surround Sound provide consistent cinema-style audio across your content using an advanced surround sound audio technology designed for evolving media. To fully enjoy the experience you need to be equiped with adapted audio installations : home theater equipment, such as A/V receivers, Blu-ray™ players, or TVs with Dolby Digital Plus.
If you prefer lossless audio, then choose DTS-HD Master Audio format.