Best Solution: Nvidia Shield Pro ← HDMI → Receiver/Soundbar ← HDMI → TV
The Shield and Xbox One are the only devices that support 4K HDR and TrueHD/dts-HD audio passthrough.
Current LG TVs do not support dts or TrueHD passthrough from TV based apps. When using the LG Plex app, both will be transcoded to a supported format. Furthermore, the LG Plex app has very limited subtitle support, generally resulting in video transcoding when subtitles are in use. See this post for additional details.
Note: Samsung TVs have the same audio passthrough restrictions as LG for TV based apps. Sony Android TVs support passthrough for dts, but not dts-HD, audio. No known TV supports TrueHD passthrough.
Current LG TVs block dts passthrough from HDMI attached devices (Shield, Roku, Blu-ray player, etc). Other TVs may block audio passthrough as well. If you need this capability, check the reviews at rtings.com prior to any purchase. They test audio passthrough from external devices.
HDMI-ARC and optical audio impose further restrictions. Neither supports lossless audio such as TrueHD or dts-HD. HDMI-ARC supports Dolby Digital, Dolby Digital Plus, and dts up to 5.1 channels. PCM is limited to 2.0 channels. Optical audio is further limited in that it does not support Dolby Digital Plus.
See [INFO] Plex, 4k, transcoding, and you - aka the rules of 4k for additional details.
