High-resolution audio is a term for music files withbit depth greater than 16-bit andsampling frequency higher than44.1 kHz or48 kHz used inCD andDVD formats. TheAudio Engineering Society (AES),Consumer Technology Association (CTA) andJapan Audio Society (JAS) set 24-bit/96 kHz as the minimum requirement to fulfill the standard.[1][2][3]The Recording Academy Producers & Engineers Wing also cites 24-bit/96 kHz as the preferred resolution for tracking, mixing and mastering audio.[4] It is supported by media formats such asDVD-Audio,DualDisc andHigh Fidelity Pure Audio, download stores likeBandcamp,HDtracks andQobuz, and streaming platforms includingApple Music,Amazon Music andTidal. Research into high-resolution audio began in the late 1980s and recordings were made available on the consumer market in 1996.[5]
Other bit depth/sample rate combinations that are often marketed as "high-resolution" include 1-bit/2.8224 MHz (DSD), 20-bit/44.1 kHz (HDCD), 24-bit/44.1, 88.2 or 176.4 kHz, 24-bit/48, 96 or 192 kHz,[6] and 24-bit/352.8 kHz (DXD). Reference-gradedigital-to-analog converters that oversample to very high rates such as 24-bit/384 kHz, 32-bit/384 kHz and 32-bit/768 kHz are also available for both consumer and professional use.[7][8] Sony'sLDAC, Dolby'sDigital Plus and Lenbrook'sMQA are marketed as "hi-res,"[9][10][11] however, these codecs employlossy compression and can often have lower bit rates thanCompact Disc Digital Audio, and thus, cannot be classified as "true high-resolution."[12][13][14]
High-resolution audio is generally used to refer to audio files that have a higher sample rate and/or bit depth than that ofCompact Disc Digital Audio (CD-DA), which operates at 44.1 kHz/16-bit.[15]
TheRecording Industry Association of America (RIAA), in cooperation with theConsumer Electronics Association, DEG: The Digital Entertainment Group, and The Recording Academy Producers & Engineers Wing, formulated the following definition of high-resolution audio in June 2014: "lossless audio capable of reproducing the full spectrum of sound from recordings which have been mastered from better than CD quality music sources which represent what the artists, producers and engineers originally intended."[16]
File formats capable of storing high-resolution audio includeFLAC,ALAC,WAV,AIFF,MQA andDSD (the format used bySACD).[17]
One of the first attempts to market high-resolution audio wasHigh Definition Compatible Digital in 1995, an encoding/decoding technique using standard CD audio.[18] This was followed by two moreoptical disc formats claiming sonic superiority over CD-DA:SACD in 1999, andDVD-Audio in 2000. These formats offer additional benefits such as multi-channelsurround sound. Following aformat war, none of these achieved widespread adoption.[19]
Following the rise in online music retailing at the start of the 21st century, high-resolution audio downloads were introduced byHDtracks starting in 2008.[19][20]
Further attempts to market high-resolution audio on optical disc followed with Pure AudioBlu-ray in 2009, andHigh Fidelity Pure Audio in 2013.[21] Competition in online high-resolution audio retail stepped-up in 2014 with the announcement ofNeil Young'sPono service.[22]
In 2014, the Japan Electronics and Information Technology Industries Association (JEITA) announced a specification and accompanying "Hi-Res AUDIO" logo for consumer audio products, administered by theJapan Audio Society (JAS). The standard sets minimums of 96 kHz sample rate and 24-bit depth, and for analog processes, 40 kHz.[23] The related "Hi-Res Audio Wireless" standard additionally requires support for theLDAC,LHDC,LC3plus andMQair codecs.[23] Sony reaffirmed its commitment towards the development in the high-resolution audio segment by offering a slew of Hi-Res Audio products.[24][failed verification]
As of 2021[update], somemusic streaming services such asTidal,Qobuz,Amazon Music, andApple Music have options to enable the playback of high-resolution audio files.[25]
Whether there is any benefit to high-resolution audio over CD-DA is controversial, with some sources claiming sonic superiority:
...and with other opinions ranging from skeptical to highly critical:
Business magazineBloomberg 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."[29]
High-resolution files that are downloaded from niche websites that cater toaudiophile listeners often include differentmastering in the release – thus many comparisons of CD to these releases are evaluating differences in mastering, rather than bit depth.[30]
Most early papers using blind listening tests concluded that differences are not audible by the sample of listeners taking the test.[31]Blind tests have shown that musicians and composers are unable to distinguish higher resolutions from 16-bit audio at 48 kHz.[32] One 2014 paper showed thatdithering using outdated methods[a] produces audible artifacts in blind listening tests.[33]
Joshua Reiss performed a meta-analysis on 20 of published tests, saying that trained listeners could distinguish between hi-resolution recordings and their CD equivalents under blind conditions. In a paper published in the July 2016 issue of the AES Journal,[34] Reiss says that, although the individual tests had mixed results, and that the effect was "small and difficult to detect," the overall result was that trained listeners could distinguish between high-resolution recordings and their CD equivalents under blind conditions: "Overall, there was a small but statistically significant ability to discriminate between standard-quality audio (44.1 or 48 kHz, 16 bit) and high-resolution audio (beyond standard quality). When subjects were trained, the ability to discriminate was far more significant." Hiroshi Nittono pointed out that the results in Reiss's paper showed that the ability to distinguish hi resolution audio from CD quality audio "was only slightly better than chance".[35]
Some technical explanations for sonic superiority cite the improvedtime domainimpulse response of theanti-aliasing filter allowed by higher sample rates. This reduces the energy spread in time from transient signals such as plucking a string or striking a cymbal.[36][37]
High-resolution audio is a new industry marketing term
HDCD is capable of higher quality sound reproduction because HDCD encodes the equivalent of 20 bits worth of data
HDtracks pioneered high-resolution audio via download
He'll have some competition. Already, services like HDtracks.com have seen triple-digit growth in downloads of top-notch digital files
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