I am experiencing S/PDIF output issues with Windows Media Player and the NVIDIA Purevideo Decoder software.
Sound cards support two mode SPDIF audio renderer modes which are DirectSound and WaveOut. Some audio chips require the use of WaveOut instead of the DirectSound renderer to get SPDIF output to work properly. Windows Media Player doesn’t support the Waveout option and only supports DirectSound via SPDIF. You will experience problems such as 2-channel audio, or no audio at all when expecting full 5.1 audio. This is an issue that the NVIDIA PureVideo Decoder cannot control. Please use a supported audio card listed in the Decoder System Requirements to avoid these problems: