I've attempted to get audio passthrough working (with the latest nightly build) on the second hdmi port (HDMI 2) without success, the avr (Denon AVR-4308) is detected in libreelec however no audio is sent to the receiver (video is sent to HMDI 1 which is working), have I misunderstood the passthrough feature? Thank you
I don't think there is any suggestion that you can take video from HDMI1 and audio from HDMI2 ?
The HD Audio passthrough option adds the option for 1080p modes (but not 2160p?) to bitstream passthrough HD Audio codecs like Dolby True HD and DTS HD Master Audio and High Resolution Audio (sending the compressed bitstream to your AVR for your AVR to decode to PCM), whereas previously on the Pi they had been decoded in software within Kodi and output as PCM 5.1/7.1 (which apart from Atmos should be lossless - other than losing metadata that some downstream AVR processing may use for loudness control etc.)