High-resolution 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.^[1][2]

Definition

Approximate dynamic range and bandwidths of some high-resolution audio formats

There is no standard definition for what constitutes high-resolution audio,^[3] 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).^[2] This includes pulse-code modulation (PCM) encoded audio with sampling rates greater than 44100 Hz and with bit-depths greater than 16,^[2] or their equivalents using other encoding techniques such as pulse-density modulation (PDM).^[3]

Although there is no firm definition, Sony describes high-resolution audio devices as those that deliver audio that’s clearer, sharper and more complex than other music sources and closer to the original.^[4]

High-resolution audio file formats include FLAC, ALAC, WAV, AIFF and DSD, the format used by Super Audio Compact Discs (SACD).^[3] 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.

History

One of the first attempts to market high-resolution audio was High Definition Compatible Digital in 1995.^[5] This was followed by three more optical disc formats claiming sonic superiority over CD-DA: DAD in 1998, SACD in 1999, and DVD-Audio in 2000. None of these achieved widespread adoption.^[6]

Following the rise in online music retailing at the start of the 21st century, high-resolution audio downloads were introduced by HDtracks^[6] starting 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.^[7] Competition in online high-resolution audio retail stepped-up in 2014 with the announcement of Neil Young's Pono service.^[8]

Controversy

Whether there is any benefit to high-resolution audio over CD-DA is controversial, with some sources claiming sonic superiority:

• "The DSD process used for producing SACDs captures more of the nuances from a performance and reproduces them with a clarity and transparency not possible with CD.^[9]—The Mariinsky Label.
• "24-bit/96kHz or 24-bit/192kHz files more closely replicate the sound quality that the musicians and engineers were working with in the studio"—What Hi-Fi?.^[3]

and with other opinions ranging from skeptical to highly critical:

• "If they [the music business] cared about sound quality in the first place, they would make all of the releases sound great in every format they sell: MP3, FLAC, CD, iTunes, or LP."—cnet^[10]
• "Impractical overkill that nobody can afford"—Gizmodo^[2]
• “A solution to a problem that doesn’t exist, a business model based on wilful ignorance and scamming people.”—Xiph.org^[11]

Business magazine Bloomberg Businessweek suggests that caution is in order with regard to high-resolution audio: "There is reason to be wary, given consumer electronics companies’ history of pushing advancements whose main virtue is to require everyone to buy new gadgets."^[12]

There are few scientific papers about the possible superiority of Hi-res audio over CD-DA. Analysis at the sample level does show that high-resolution audio files have a higher measure of conditional entropy than CD or MP3 files, an indication that the high-resolution files contain more information.^[13] High resolution files can sound different because they bypass processing done to the master for the mass market CD release, such as Loudness war compression. Albums have even been released with distinct versions aimed at the popular market and those wanting less mastering changes.^[14]

Most early papers using blind listening tests concluded that differences are not audible by the sample of listeners taking the test .^[15] Blind tests have shown that musicians and composers are unable to distinguish higher resolutions from 16-bits 48 kHz^[16] The filters used to convert higher resolution audio down to standard CD quality can produce audible artifacts in blind listening tests.^[17]

Notes

1. Shankland, Stephen. "Sound bite: Despite Pono's promise, experts pan HD audioSound bite: Despite Pono's promise, experts pan HD audio". c|net. CBS Interactive Inc. Retrieved 22 March 2014. the "HD audio" movement also called high-resolution or high-definition audio
2. Aguilar, Mario (June 2013). "What Is High-Resolution Audio?". Gizmodo. Gawker Media. Retrieved 17 March 2014. High-resolution audio is a new industry marketing term
3. "High-resolution audio: everything you need to know". What Hi-Fi?. Haymarket Publishing. 10 Mar 2014. Retrieved 17 March 2014. there’s no universal standard for high-res audio
4. "Sound Technology: Listening defined and redefined". Sony Mobile. Retrieved 5 May 2016. deliver audio that’s clearer, sharper and more complex than other music sources and closer to the original
5. "Home Technology eMagazine - Classic Home Toys Installment #19 The Final CD Format: HDCD". HomeToys. Retrieved 2012-08-05. HDCD is capable of higher quality sound reproduction because HDCD encodes the equivalent of 20 bits worth of data
6. "Definition of:high-resolution audio". PCMag. Ziff Davis. Retrieved 18 March 2014. HDtracks (http://www.hdtracks.com) pioneered high-resolution audio via download
7. "Universal Music bets on consumer longing for quality with hi-fi Pure Audio". DVD & Beyond. Globalcom Limited. Retrieved 4 January 2014.
8. O'Malley Greenburg, Zack. "How Neil Young's Pono Music Raised $2 Million in Two Days". Forbes. Forbes.com LLC. Retrieved 15 March 2014. He’ll have some competition. Already, services like HDtracks.com have seen triple-digit growth in downloads of top-notch digital files
9. "What are the benefits of SACD?" Mariinsky Label FAQ" Retrieved January 1, 2014.
10. Guttenberg, Steve. "What's up with Neil Young's Pono high-resolution music system?". c|net. CBS Interactive Inc. Retrieved 18 March 2014.
11. "Guest Opinion: Why 24/192 Music Downloads Make No Sense". evolver.fm. The Echo Nest. Retrieved 18 March 2014.
12. Brustein, Joshua. "Music Snobs, Neil Young Has a Product for You". BLOOMBERG BUSINESSWEEK. BLOOMBERG L.P. Retrieved 17 March 2014.
13. McCaulay, Scott. "Has Digital Audio Taken the Surprise Out of Music?". doi:10.13140/RG.2.1.2268.5284.
14. "nine inch nails: hesitation marks (audiophile mastered version)". Retrieved 9 November 2015.
15. "Audibility of a CD-Standard A/D/A Loop Inserted into High-Resolution Audio Playback" (PDF). J. Audio Eng. Soc.,. Retrieved 24 March 2015.
16. On a testé... la musique en haute définition.
17. "The Audibility of Typical Digital Audio Filters in a High-Fidelity Playback System". J. Audio Eng. Soc.,. Retrieved 9 November 2015.