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.

Consider the following scenario. On a computer that is running Windows Vista, you open the Sound item in Control Panel. Then, you open the Properties dialog box for an installed device that uses one of the following interface formats:

• High-Definition Multimedia Interface (HDMI)
• Sony/Philips Digital Interface (S/PDIF)

However, when you click the Supported Formats tab in the Properties dialog box for the device, you notice that all the check boxes are unexpectedly selected. For example, the following check boxes are selected:

• DTS Audio
• Dolby Digital
• Microsoft WMA Audio
• 44.1 KHz
• 48.0 KHz
• 88.2 KHz
• 96.0 KHz
• 176.4 KHz
• 192.0 KHz

You experience this problem even though the following conditions are true:

• You did not select all the check boxes.
• The device does not support all these selected formats.

When this problem occurs, you may not receive sound from the device.