What is hi-res audio?
High-resolution audio, also known as High-definition audio or HD audio, is a marketing term used by some recorded-music retailers and high-fidelity sound reproduction equipment vendors.
There is no standard definition for what constitutes high-resolution audio but it is generally used to describe audio signals with bandwidth and/or dynamic range greater than that of Compact Disc Digital Audio (CD-DA).This includes pulse-code modulation (PCM) encoded audio with sampling rates greater than44100 Hz and with bit-depths greater than 16, or their equivalents using other encoding techniques such as pulse-density modulation (PDM). High-resolution audio file formats include FLAC, ALAC, WAV, AIFF and DSD, the format used by Super Audio Compact Discs (SACD). It should be noted, however, that audio encoded into one of these file formats is not necessarily high-resolution audio. For example, a WAV file could contain audio sampled at 11,025 Hz and quantized at eight bits, which is lower quality than CD-DA.
One of the first attempts to market high-resolution audio was High Definition Compatible Digital in 1995. This was followed by two more optical disc formats claiming sonic superiority over CD-DA: SACD in 1999, and DVD-Audio in 2000. None of these achieved widespread adoption. Following the rise in online music retailing at the start of the 21st century, high-resolution audio downloads were introduced by HDtracksstarting in 2008.Further attempts to market high-resolution audio on optical disc followed with Pure Audio Blu-ray in 2009, and High Fidelity Pure Audio in 2013. Competition in online high-resolution audio retail stepped-up in 2014 with the announcement of Neil Young's Pono service