PowerDVD send LPCM 2ch audio to AV receiver via SPDIF.
PowerDVD down-samples HD audio from Blu-ray Discs to 48 KHz / 16-bit.
This is because the un-protected digital audio cannot output due to the AACS requirements.
A Windows PC lacks an internal secure audio path, that’s why your receiver does not receive the original audio bit stream.
CyberLink is working with audio chip vendors to enable the proprietary interface for encryption of audio bus.