You install a High Definition (HD) Audio function driver on a Windows Vista-based or Windows Server 2008-based computer. The driver can expose multiple non-Pulse Code Modulation (PCM) audio formats and some PCM or non-PCM audio formats that are encrypted.

However, you may notice that the audio application cannot play the following formats:

• The latest non-PCM formats, such as Dolby True HD
• Both PCM and non-PCM audio formats that are encrypted

When you select the DTS Audio option in the SPDIF Out Properties dialog box for an audio device in Windows Vista, the device may output PCM (pulse-code modulation) audio instead of DTS (Digital Theatre System) audio from the Sony/Philips Digital Interface Format (S/PDIF) connection. Therefore, you may hear a stereo signal instead of a signal that uses additional channels. Or, you may hear no sound at all. When you select the DTS Audio option, you expect to hear 5.1-channel audio output or another DTS signal.

Note: The symptoms of this problem may vary, depending on the specific configuration. For example, any of the following may affect this scenario:

• In most cases, DTS is used to store 5.1-channel audio. However, DTS also supports 2-channel stereo.
• A program that plays DVDs, such as Windows Media Center, may only output DTS audio when it is configured to do this. This behavior may affect what you hear. For example, you may hear no audio from the DVD when this problem occurs.
• Windows Vista tries to use PCM audio for error dialog box notifications. Therefore, you may hear these notifications on a home theater system when this problem occurs.