[noggin]

For HD audio, where I can appreciate DTS-MA or TrueHD are concert Blu-rays (The Dave Matthews Radio City disc comes to mind), and in action movies with deep bass or peaks where audio might slightly clip otherwise ('John Wick' comes to mind), and in movies where dialogue comes in so crisp. But, in the end analysis, in A/B blind tests, most of us would probably not be able to always tell the difference. Sometimes, yes.

It all depends what aspect of HD audio on Blu-ray you're after. The fact that it's >16 bits/44.1 (or 48kHz) or that its lossless. Most Blu-Ray discs don't have lossless tracks that are >48kHz, but a lot are >16bits. The Dave Matthews & Tim Reynolds Radio City disc is one of the exceptions with a 5.1 24/96 audio track. However, it's extremely unlikely that anyone could A/B/X it from a lossless 16/48 version of the same thing without listening to very quiet parts of the soundtrack at extreme volumes. A 1.5Mbit lossy DTS or 640kbit AC3 track is another question.

FWIW, most of the time when I see someone talking about HD audio on these various boxes they're referring to the ability to bitstream the audio tracks found on Blu-ray discs over HDMI, or properly decode them to PCM rather than just the lossy core. I don't presume they're specifically after the fact that it's higher than CD quality and that they believe they can hear the difference.

Yep - I'm not, personally, convinced of the benefit of >48KHz sampling or >16 bit depth for final releases (though can see the logic in recording at >16 bit to give you scaling latitude in a mix down). However I can definitely see the benefit in going for a lossless compression scheme, or straight PCM, to avoid some of the processing that lossy compression introduces.

I've heard some really horrid 384k and 448k DD encodes, and even 640k DD doesn't always sound as clear as a True HD or DTS HD-MA track. 1.5Mbs DTS does sound very good for DVD quality - and is entirely tolerable - but why wouldn't you chose to listen to lossless audio if you had the option?

Now that you can get Dolby True HD output in PCM from a £30 Raspberry Pi 2 (and pre-process DTS-HD MA/HR content off line on a PC, Mac or x86 Linux box to FLAC so that it can be played in 5.1) why wouldn't you?