(2015-12-08, 05:14)wrxtasy Wrote: The standard AC3/Dolby Digital/DTS 5.1 lossy Audio passthrough with this device.
The eternal question is can you tell the difference anyway ?
Have you even got high quality speakers to properly hear the frequencies contained in HD Audio anyway ?
Most HD Audio tracks are 48kHz sample rate, the same as most AC3/DTS tracks - so the frequency range is no different for either format, so it isn't a case that your speakers need to cover a different frequency range (though there are some 96 and 192kHz HD Audio tracks, the vast majority are 48k) There is sometimes a bit depth difference - with HD Audio often (but not always) being 24 bit rather than 16 bit (which can mean a larger dynamic range, but in reality this may not be used).
The real difference between HD Audio and AC3/DTS is that the former delivers clean, uncompressed audio when it has been decoded, whilst the latter uses lossy compression, so some audio information is lost. The information that is lost is based on psychoacoustic compression, where the audio content that is lost should be content that you can't hear is missing. Whether this is audible or not will depend on your brain, and how you hear, and the quality of your hearing. It will also depend on the bitrates involved. There is a big difference between a 384kbps AC3 file and a 640kbps AC3 file. I've got a DVD with a 256kbps 5.1 AC3 track. It sounds marginally better than AM radio...
It's effectively the difference between listening to an uncompressed CD (or a FLAC, ALAC or WAV copy) and an MP3/AAC file with lossy compression. Lots of people chose not to compress their audio collection to avoid any potential quality loss, as a guarantee that they will never hear compromised audio. Even if in 90%, 95%, 99% of cases you can't hear the compression, some people feel that there is no point in compressing as they don't want to compromise their audio for the 10%, 5% or 1% of content that they may hear the difference.
In reality lots of cases people can't hear the difference between a high bitrate AC3/DTS track and a lossless DTS-HD MA/Dolby True HD track IF it's in the same format.
HOWEVER, all of this is moot when you move to discussing 7.1 audio and if you have a 7.1 audio system. In this case you may DEFINITELY hear a difference. This is because AC3/DTS lossy tracks are almost universally 5.1 (there are some 6.1 DTS ES tracks but they are quite rare). Lots of HD Audio is 7.1 rather than 5.1 though. If you have a 7.1 system then the lossless compression isn't the reason you want HD Audio, it's much more important aspect is that it delivers 7.1. If you are listening to a DTS/AC3 track it will be being up sampled from 5.1 to 7.1, whereas if you are listening to a lossless decoded or bitstreamed HD Audio track mastered in 7.1 you will get it natively in 7.1
If you have a new DTS:X or Dolby Atmos system then HD Audio bitstreaming is the only way of delivering the new sound formats to your audio system (lossless decoding, as used by the Pi 2) isn't suitable as there is no current solution for decoding of these formats or for carriage of them over PCM AFAIK.