Summary

After a decade of streaming dominated by the MP3, online music services are gradually imposing CD and even hi-res audio audio.Can everyone take advantage of it, how, and what benefits to expect?Here are some answers.

Source: Focal

To fully understand what CD or hi-res soundless sound, a little historical reminder is essential.We are not going to go back to the invention of the phonographer, but it is interesting to explain why the sound has become digital.Because, before that, the audio was analog, stored on supports with a limited lifespan.The vinyl record and magnetic tape cassettes were fragile and were inexorably.

In the 1970s, Philips and Sony therefore decided to work on a new perennial storage technology, which would no longer imply a furrow or magnetize a strip according to the electrical pulses of an audio signal, but to describe this signaldigitally, either in the form of 1 and 0.

The compact disc, father of all digital audio formats

In 1982, under the leadership of Philips and Sony, the Compact Disc, on which music was stored in digital form, was therefore born after sampling and quantification according to the PCM technique (Pulse Code Modulation)).

The very principle of this digitization was laid in 1960 with Shannon's theorem, which states that the description of an electrical signal requires a number of samples equivalent to double the highest frequency of this signal.As our ear perceives up to 20,000 heights of different sounds - 20,000 hertz - it is decided to take, each second, 44,100 samples for audio CDs.

CD in bulk // Source: Mati Mango via Pexels

In real time, each audio sample on this support is described with sixteen zeros and some (16 bits)), which corresponds to a binary flow of 1.411 Mbps (44100x16x2 channels)).In other words, each hertz that our ear hears is described roughly with ... 4 bytes.It’s not much, but at the time, we can't do better, and then the qualitative gap with the magnetic cassettes is striking.

An inevitable and complicated dematerialization

The advent of microcomputers with CD-ROM reader in the 1990s, will lead to the dematerialization of the CD-Audio.But there is a problem.The hard drives at the time have a capacity of only a few dozen mega-cocks, which prevents transferring the content of a CD-Audio which "weighs" around 700 MB.It is also impossible to consider streaming via the Internet, analog modems offering flows 30 times lower than that of a PCM 16/44 signal.It’s even totally utopian at the time.Finally not for everyone, because at the Fraunhöffer Institute, we work precisely in the compression of PCM signals, with a codec that will revolutionize digital sound.

The MP3 format is a real game to change: with it, flow of a 16 -bit/44.1 kHz PCM flow is reduced from 1,411 Mbps to 128 kbps, with an "acceptable" loss of quality.This division by ten of the flow implies a destructive compression (lossy in English)): certain sounds deemed not useful are simply removed, according to complex psychoacoustic models.In addition, the frequency response and the dynamic margin are reduced.Listening, music in MP3 format offers a less large sound scene, a less large and tonic serious register, as well as a reproduction of the high frequencies less fluid.

These remarks are also valid for all destructive audio codecs: the AAC worn by Apple, the vorbis used by Spotify, the Dolby AC3, or even the SBC and the APTX, reserved these for the Bluetooth transmission.Anyway, these new codecs allow you to listen to music other than with the only compact disc reader: with them are born the web radios, the iPod then the headsets wirelessly.

The boom in lossless audio compression and FLAC and ALAC files

However, other non -destructive compression methods are then developed, in order to completely preserve the integrity of the PCM 16/44 flow.In the early 2000s appeared the FLAC codecs (Free Lossless Audio Codec)) then ALAC (Apple Lossless Audio Codec)), which employ a lossless compression derived from the LZW algorithm used for data archiving (Zip, RAR, etc..)).With them, the flow of a 16 -bit CD flow to 44.1 kHz is reduced by 1,411 Mbps to average values between 600 kbps and 900 kbps - depending on the complexity of the audio signal.Bandling gain, essential for storage or streaming, is not huge, but the original quality is completely preserved.

The high-end connected speaker NAIM MU-SO 2, Hi-Res Audio Compatible // Source: NAIM

The need for HD sound

CD quality sound has always had its detractors among audiophiles, who blame it a lack of transparency and naturalness, compared to the vinyl record.In question: the sampling deemed far too low and which also attaches equal importance to all frequencies, while our ear is above all sensitive to mediums.What is more, the mathematical theorem used did not specifically deal with audio signals, but overall electrical signals.

Ainsi, dès 1999, Sony lance le Super Audio CD (SACD)), qui propulse l’échantillonnage du signal audio à 2,8 millions de prélèvements par seconde — soit 64 fois la résolution du CD-Audio.More musical, the SACD does not however affect a large audience, because it requires a very expensive specific reading plate.In addition, the album catalog is not fleshed out.However, the idea of greater sampling and quantification is making its way in recording studios.Sound engineers work with PCM flows up to 32 bits and 384 kHz.Listening - with quality equipment - the profits are obvious: transparency, increased dynamic margin and more realistic stamps.

As early as 2008, HDTRACKS offered to download albums in 24 -bit / 96 kHz FLAC format, quickly joined by Qobuz, and more recently by Tidal and Apple Music.The average speed of these FLAC or ALAC files varies from 2 to 8 Mbps, depending on the sampling level.

Do we really hear the difference between CD and Hi-Res quality?

Yes, but on the condition of using good quality listening equipment.The headphones supplied with the dammers or the miniature Bluetooth speakers are for example to be avoided, because with them, a 24 -bit Flac file 192 kHz will sound like a MP3.In addition, the way an album is masterized in the studio is very important.Some sound engineers crush the dynamics in order to promote better intelligibility on entry -level listening equipment.Others favor dynamic deviations and thus all the flavor of sound recording and the stamp of the instruments.

Not all albums are mixed with the same quality // Source: David Bartus via Pexels

To sort the good grain of the tares, you can take a look at the DR site.Loudness-War.info, which measures and indexes the dynamic margin of many albums.In short, if you listen to albums well mixed on good quality listening equipment, the sound hi-res audio makes a real difference.

The Hi-Res Audio label

Pour aider les consommateurs à identifier les baladeurs, amplis ou casques capables de prendre en charge les signaux audio HD 24 bits, un consortium industriel japonais (Jeita)) lance le label Hi-Res Audio en 2014.We then see appearing in Sony, Pioneer or Onkyo, amplifiers, helmets, walkers, smartphones or hi-res audio speakers.The common point of these devices is the native management of 24 -bit HD audio flows until 192 kHz, thanks to an integrated DAC (Digital To Analog Converter)). En outre, certains périphériques audio non numériques (casques, enceintes…)) sont également certifiés Hi-Res Audio, car leur réponse en fréquence s’étend jusqu’à 40 kHz.

However, the Hi-Res Audio label is a paid license that some manufacturers renounce to acquire, while their products are however capable of taking charge of 24-bit audio flows and 192 kHz.For example, all Android 10 smartphones support HD audio.

To summarize, we talk about:

How to enjoy music in CD or hi-res quality?

First of all, it is necessary to take out a subscription to an online music service, offering streaming or download in CD or hi-res quality.Apple Music, Qobuz, Tidal, Amazon Music or Deezer are among the possible choices.Spotify should soon follow.Then several configurations are possible.

To go further Spotify vs Deezer vs Apple Music…: What music streaming service to choose?

With a bluetooth smartphone

From the iPhone 7, the trend is clearly the abolition of the mini-jack headphone output, in favor of a sound transmission in Bluetooth.Unfortunately, the evolution of the Bluetooth standard does not go in the direction of an increase in the bandwidth devolved to the audio, but on the contrary towards a reduction in energy consumption - to preserve the batteries of smartphones, helmetsand Bluetooth headphones.

Depuis 15 ans, la bande passante exploitable pour l’audio (profil A2DP)) n’a que peu évolué et aucun fabricant ne s’est risqué à exploiter de débit supérieur à 1 Mbps, faute de stabilité.On paper, it is enough to transfer a compressed CD quality flow without loss.Moreover, the LDAC and LHDC codecs operate up to around 900 kbps of bandwidth and offer loss -free transmission in Bluetooth.But in practice, this flow is dynamically reduced, when the radio link is bad.In this case, compression becomes deteriorating.As for hi-res audio, no Bluetooth codec allows it to be transmitted without loss.

The Sony Wh-1000X4 Bluetooth helmet, compatible with CD quality transmission LDAC // Source: Sony

Here is a little reminder of the main Bluetooth audio codecs and their capacities:

To go more LANAPTX, LDAC, SBC: Understanding everything to Bluetooth Audio Codecs

Assessment, Lossless audio in Bluetooth, it is possible, but only in CD quality, with the LDAC and LHDC codec, and provided that the radio link is not disturbed.In public transport, it is clearly mission impossible.

With a headphone output smartphone

All smartphones running Android 10 and following support CD and HD quality flows, up to 24 bits and 192 kHz.Models with mini-jack output can be used with helmet or wired headphones.The DAC, integrated into the SOC is very good, but the headphone amplifier, also integrated into the SOC, is designed to consume as little current possible.Therefore, audio performance is good, without being exceptional.

With a smartphone and an external DAC

A more qualitative solution consists in outsourcing digital analogical conversion, as well as the food of the helmet or headphones.For this, it is necessary to use an external DAC.This can be the USB-C adapter supplied with certain smartphones, which incorporate a DAC and a miniaturized headphone amplifier, HD audio compatible up to 24 bits and 192 kHz. La qualité de ce genre d’adaptateur est moyenne et, pour profiter d’un son plus charpenté et défini, mieux vaut se tourner vers des DAC nomades, par exemple ceux de fabricants tels qu’Astell&Kern, Audioquest, FiiO ou iBasso.

The DAC and amplifier Nomadic helmet FIIO Q1 Mark II is compatible hi-res Audio // Source: FIIO

With an audiophile player

Designed to read CD and HD quality audio files from a memory card, the traders most often embark on a pair of DACS - one per channel - to reduce distortion and improve the separation of channels.Their headphone amplifier is calibrated to supply the headphones as much as the helmets deemed to be difficult to pilot.Finally, these nomadic readers can transform into external USB DAC and operate a peer with a smartphone, or any computer. Astell&Kern, FiiO, iBasso, mais aussi Cowon ou Sony sont spécialisés dans la conception de baladeurs audiophiles.

Le baladeur audiophile Baladeur Astell&Kern Norma SR25 // Source : Astell&Kern

With a connected speaker

Most Wi-Fi speakers are compatible with Lossless audio, most often via owner transmission protocols: Apple Airplay 2, Yamaha Musiccast, Google Chromecast or Sonos.To listen to music in CD or HD Lossless quality, you must be subscribed to an adequate streaming service and control the speaker with your smartphone.But we must not wait for mountains and wonders of this type of speaker, which are used more to produce a sound atmosphere than to create a precise and realistic scene.With them, the difference between his compressed and Lossless is only rarely obvious.But there are exceptions: Naim Mu-So 2, Cabasse The Pearl or Devialet Phantom, for example.

With a connected amplifier and hi-fi speakers

If your wish is to use a smartphone to listen to music streaming on acoustic speakers, the choice of reason is that of a connected hi-fi amplifier.Embedded components, including DAC, are served by a generous power supply, which optimizes how it works.This type of amplifier is offered by the major brands of the hi-fi that are Yamaha, Denon, Marantz, Rotel or Nad.Most integrate the main streaming protocols.And if you set your sights on an old-fashioned hi-fi amplifier, without DAC or Wi-Fi, it is always possible to add an Apple Apple Airplay 2, Yamaha Musiccast or Google Chromecast network reader..

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