[noggin]

Pi2 does have HD audio, for up to 7.1 channels. Just no ATMOS and DTS:X, which are the newest extensions for HD audio.

What about DTS HD MA and DOLBY TRUEHD?

Both are supported with lossless decode to multichannel PCM with one limitation for rare 192kHz mulitchannel audio. To all intents and purposes, for nearly every DTS HD MA / Dolby True HD track released on Blu-ray, you will get lossless decoding.

There is a hardware limitation in the Pi and Pi 2 that means 192kHz tracks are limited to 4.0 or less, but 48/96kHz stuff works up to 7.1 (and 192kHz >4.0 stuff can be down sampled). 16-24 bit audio is supported at all sampling rates I believe.

This also means that the Pi / Pi 2 will play FLAC multichannel over PCM, as well as handle multichannel lossy AAC stuff (and other codecs that can't be bitstreamed) - which is great for Freeview HD in the UK.