What You Need to Know About Hi-Res Audio

What is Hi-Res Audio?
Hi-Res Audio (HRA) music files offer the highest digital sound quality while retaining the typical benefits of digital audio, such as portability and accessibility. HRA delivers discernible sonic benefits over compressed digital audio formats and can exceed the quality of Compact Discs.

What audible benefits does Hi-Res Audio provide?
Hi-Res Audio tracks, when developed from an appropriately high-quality digital or analog master recording, can render noticeable improvements in sonic detail, dynamics, instrument and vocal timbre, and soundstaging/imaging compared with MP3s, CDs or streamed Internet music. Since hi-res music tracks can be a precise duplicate of an original hi-res digital master or better capture the inherent quality of an analog master, Hi-Res Audio allows music to be heard as the artists originally intended.

Why should consumers care about Hi-Res Audio?
With the growing popularity of compressed digital downloads from online music stores and compressed live streams from popular Internet music services, consumers have been sacrificing sound quality for convenience. Hi-Res Audio represents an opportunity for consumers to get closer to a studio experience and hear more emotionally engaging music.

Do I need to be a techie to get into Hi-Res Audio?
No, but a quick primer can help you better understand the key features that make audio “high resolution.”

To begin, all sounds start out analog and can be represented by a single, varying waveform that changes over time—think of a long undulating string, or a continuous sine wave.

Digital audio systems work by capturing a series of snapshots of these analog waveforms over regular intervals, much the way a digital video camera captures individual still frames over time. Each of these audio “samples” measures the waveform’s voltage at a precise moment. That information is converted into data by a device called an “analog-to-digital converter” and then stored in computer memory.

With audio, the rate at which you measure the waveform is called the “sample rate.” A CD-based system samples the waveform 44,100 times a second, while Hi-Res Audio typically measures a waveform 96,000 or even 192,000 times a second. This higher sample rate allows more faithful recording of much higher frequencies, resulting in a vastly larger audio bandwidth.

To play back the samples, the voltages are read at the same rate and same order in which they were stored. A digital-to-analog converter is used to reconstruct the original analog waveform, which can then drive speakers and headphones that transform the signal into back into sound waves.

Another hi-res spec called “bit depth” indicates the resolution of each waveform measurement. The anal- ogy here is similar to the number of possible colors available for each pixel in a photo; the more colors, the more realistic and subtle the visual presentation. The CD has a bit depth of 16 bits, which can resolve about 65,000 different voltage values. Hi-Res Audio typically has a bit depth of 24 bits, which can theoretically resolve almost 17,000,000 different values (practically, it’s less, but still more than a CD).

Most digital audio recordings are stored in a form called PCM, or pulse code modulation. You’ll often see hi-res music tracks described, for example, as “96/24 PCM” and packaged for download as either an uncompressed PCM file type such as WAV or AIFF, or as a lossless compressed file type such as FLAC or ALAC.

Another lossless, hi-res digital audio format called Direct Stream Digital, or DSD, captures only 1-bit samples, but at very high sampling rates, typically 2.8 or 5.6 million per second. You’ll often see these described, for example, as “DSD 2.8.”

Note that DSD is the same format as that used on SACD optical audio discs and qualifies those discs as HRA. Uncompressed hi-res music files, sometimes called LPCM, are often distributed on DVD and Blu-ray optical discs as well.

How does CTA define Hi-Res Audio?
To ensure consistency, the Consumer Tech- nology Association (CTA), the Digital Entertainment Group (DEG), the Recording Academy Producers & Engineers Wing, and various music labels have joined together to create a technical definition of Hi-Res Audio. According to CTA:

“High-Resolution Audio is lossless audio that is capable of reproducing the full range of sound from recordings that have been mastered from better than CD quality music sources.”

Additionally, there are four Master Quality Recording categories to help describe the provenance, or origin of Hi-Res Audio files. These are: MQ-P (from a PCM digital master at no less than 48 kHz/20-bit); MQ-A (analog master); MQ-C (upsampled from a 44.1 kHz/16-bit CD quality master); and MQ-D (DSD master).

What equipment do you need to enjoy Hi-Res Audio?
Better audio playback gear will make the benefits of hi-res files more evident, though an expensive audiophile sound system is not required. Hi-res players, premium headphones, DACs and high-quality powered or passive speakers are among the products that support Hi-Res Audio.

Is hi-res playback supported for home, portable and car audio?
Yes to all three. A home hi-res library can be mated to a DAC and home audio system, and there are A/V receivers, integrated amplifiers and even wireless multi-room audio systems now with built-in hi-res DACs. Portable players are avail- able at varying prices and can be plugged into today’s premium car audio systems for hi-res music on the road, and there are now hi- res-compatible in-dash players.

Where can listeners acquire hi-res music?
Several online music stores specialize in offering a wide variety of hi-res music today. Chief among them are HDtracks.com, SuperHiRez.com, iTrax, Onkyo, and Neil Young’s Pono.com music store. There are also many specialty and independent audiophile recording labels who offer their own libraries for sale. Beyond this, many of the major and smaller music labels provide hi-res music on disc-based media such as SACD, Blu-ray and DVD. The website findHDmusic.com offers an updated list of hi-res music stores.

Are there streaming music options for hi-res listening?
The higher bandwidth requirements of Hi-Res Audio, coupled with low consumer awareness, to date have kept the most popular online music services from offering hi-res streams. It is hoped that more services will get on board as lossless compression technology improves, bandwidth becomes cheaper and consumer demand for Hi-Res Audio grows.

What kind of music content is available in hi-res?
Whatever kind of music you love, you’re likely to find a good representation at the largest hi-res music stores. The major record labels have caught on to the opportunity represented by Hi-Res Audio and moved aggressively to remaster and rerelease many classic back-catalog titles through these retail channels. Simultaneously, many of today’s artists are making new music available in Hi-Res Audio formats as well.

Fetuso's picture

Crummy recording = crummy sound. Regardless of sample rates. Too much dynamic range compression is a far greater evil than data compression. High Res audio will do nothing to save music from that.

ezraz's picture

that's a totally different issue.

it's valid, you may be right that it's a big problem of new bands. but all the classic music that's already been recorded properly? that's about distribution formats, that's what hi-res is about.

it's been around for 20+ years, this is about what consumers can finally buy affordably and play back properly. if artists make crap sounding records that's on them, a better distro format might help in the long run but not immediately for everyone.

mlknez's picture

This article has so many inaccuracies, that it would take another article to explain. According to the article, any recording ever made can be considered "Hi-Res" if it is put in a big enough container. I guess that 1902 Edison wax cylinder is "Hi-Res" when put into a 96khz/24 bit flac file. Ha Ha.

ezraz's picture

hi res digital is digital domain, has nothing to do with analog.

this is about letting consumers finally hear the best digital masters, and what is possible beyond 16/44. many people have never heard it: for them CD is the single gold standard. anyone that's been in a studio knows that's false and that most stuff is reduced as the last step for consumer CD.

these days it's reduced AGAIN to mp3 or aac and taken back to <10% of original data. that's pretty sick considering it's for no good reason anymore, than simple storage economy equalling pennies of space.

Hi Res Audio is about reversing a trend, and that's never easy. Convenience is still there - I have almost all lossless and I have at least a 1000 albums loaded in my PonoPlayer at any moment, with another few thousand on cards the size of my toenail. that's crazy convenient, and i'm not renting that stuff for $0.000000002. i paid for it properly.

ezraz's picture

so many desktop experts these days. hi-res has been around since the beginning -- 16/44 was an arbitrary number picked for both practical and ridiculous reasons, and all this mumbo jumbo about what people can and can't hear is just that.

pro studios have been at 24bit for damn near 20 years now. the record labels started moving their archive systems to 24bit in the 90's. consumers haven't had it because you need a decent DAC and analog signal chain to hear the difference between 24bit and 16bit. 16bit was picked because it's so much smaller and is hard to define what is lost when you downsample and dither.

but the loss is there, going from 16,000,000 data points to 64,000 does not come without some data loss!

if the record was tracked and/or mixed and/or mastered in a 24bit environment, that is the best copy available, and can now FINALLY be offered to discerning consumers like me and you.