What You Need to Know About 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.