I can conclusively confirm that when playing virgin rip bluray titles on a computer using a HDMI video and audio output capable graphics card, a Samsung PS50C550 Plasma TV will passthrough digital audio to a 5.1 amplifier via the Samsung TV SPDIF output. Therefore; the Samsung PS50C550 Plasma TV was manufactured for SPDIF output passthrough.
When playing the same virgin rip bluray titles through the WDTV Live, some of the titles will passthrough digital audio and others will not. The issue is with the bluray title menu structure. When an m2ts file is played outside the bluray title menu structure, the file structure copy protect stops the m2ts file audio playback. Digital ripping will not pick up that copy protection because the title author used Java programming in the bluray title compilation.
I purchased a Samsung PS50C550 Plasma TV to watch a virgin source high definition video not compressed video. It would have be cheaper to pay the DVD and bluray title playback royalties as it would have eliminated having to purchase a stand alone bluray player and building a HTPC to just play bluray titles.
WD state that the WDTV Live is not licensed for bluray title playback. Maybe the resolution is to manufacture the WDTV Live in two versions; royalty paid DVD and bluray title playback and general purpose video streaming.