All about High Resolution Audio
By Rob Stewart - JustMastering.com
What is high-resolution audio?
Several record labels and consumer electronics companies met in June 2014 to discuss and agree to a formal definition for high-resolution audio. This was an important development because the compact disc has been with us since 1982, and a lot has changed in digital audio over the last few decades. Here is the official definition of "High-resolution Audio" as of 2014:
- 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."
You may be thinking that this is all about marketing, and I think that is a fair judgement in some ways. There are two key themes in the statement above that I should highlight:
- "Lossless" - i.e. a delivery format that does not use any form of data compression which would degrade the audio quality.
- "Reproducing the full range of sound" - a more technical attribute, and sadly the benefit is not obvious to every listener, depending upon their playback system. This statement is saying that the recording technology that is available today is capable of capturing a lot more information and detail than what older digital formats were capable of.
If I were part of this group, I would have suggested that we have two definitions to help educate the industry and listeners. By separating what defines high-resolution delivery from high-resolution audio, we can help prevent misunderstanding. Here is how I would separate and define high resolution audio formats versus high resolution audio:
- "A high-resolution audio format is capable of storing all audible details, i.e. the full dynamic and spectral range of any recording, regardless of its age or source."
- "A high-resolution audio recording demonstrates a faithful capture of a performance, by containing the lowest possible amount of added noise and distortion, while containing the widest possible dynamic and frequency range of the performance within the technical limitations of the recording medium or production process used at the time of capture."
I'll explain my reasoning about the definitions below, but for the time being, let's get back to the different High Resolution Audio formats as defined by the working group.
What am I getting when I purchase a high-resolution release?
Frankly, it depends! There are several variables at play, and I have a few concerns that I will discuss further, below. To help address the different variables, the working group has defined four different "Master Quality" (MQ) categories of high-resolution audio, as follows:
What is the MQA format? Is that the same as MQ-A?
No. MQA or "Master Quality Authenticated" is a completely different thing from MQ-A or "Master Quality - Analog Master Source".
- MQA is not a designation the way that the MQ ratings are, above. MQA is a technical modification that can be applied to a file format. That is to say, you playback the MQA encoded audio using a player equipped with an MQA decoder.
- The MQ-A, C, D and P ratings above are agnostic to the file format itself. They are used to tell you the path that the recording took in getting to the high resolution audio format (was it originally analog, or digital for example).
What is MQA for, then?
MQA is intended to make high resolution audio both compact and "streamable" so that it can be enjoyed on a wide variety of playback systems, including mobile devices. You can read more detail about it on MQA-inventor Bob Stuart's website, here.
What consumers need to know about MQA, MQ High Resolution Audio Ratings
- MQA is one solution to an important technical problem: Making high resolution music portable.
- You do not need an MQA compatible player to play a high resolution audio file in any of the MQ-A, C, P or D designations.
- You only need an MQA compatible player if you want to play the MQA-encoded portion of an MQA-encoded audio file.
- MQA is not technically lossless. The MQA encoding process degrades the audio quality for those who do not have a player equipped with an MQA decoder. You can find more information about that in John Siau's (Benchmark Media Systems, Inc.) article, here.
- According to John's article, you lose the benefits of MQA if you use room correction or other digital processing (even something as simple as a digital volume control) between the source file, and the final Digital-to-Audio conversion step.
Because the different MQ (Master Quality) designations apply based on the source master, there is some potential for misunderstanding.
- you could produce a release entirely in the analog domain, to an analog tape, and then digitally master it at 24-bit/96kHz PCM. That therefore would give it the "High Resolution" designation of "MQ-P"
- you could record and produce a release entirely in the digital domain using a PCM-based multi-track recorder, and then master it to analog tape. This would give it the "High Resolution" designation of "MQ-A"
- you could produce a release entirely in the PCM digital domain, and then convert it to DSD, which would therefore give it the designation of "MQ-D"
- you could produce a release from a 16-bit 44.1kHz master that was upsampled to 24-bit 96kHz, giving it the designation of "MQ-C"
How can a 16-bit CD master source be considered "high resolution"?
By the working group's definition, it cannot. It is considered "standard" resolution, but, remember that the MQ-C label is a designation tells you what the master source was. In this case, the master source was an upsampled version of the CD master (or any 16-bit 44.1kHz source file, for that matter). There are technical and sonic advantages to upsampling standard resolution files prior to mastering, such as lower distortion. Does this automatically mean that an MQ-C High resolution release will sound better than a 16-bit 44.1kHz master? It depends upon the mastering process that was used in each case, and, whether the project is a remaster from a previous CD master (two different mastering stages at two points in time), versus simply a master that was made from a 16-bit mix file (i.e. only one mastering stage). We can hope that any documentation that the label provides with the release would cover this for listeners who want to know more about the recording.
what's wrong with CDs? Mine still sound fantastic.
Absolutely nothing. CDs were designed to last for a lifetime of use thanks to the fact that nothing (other than our hands!) touches the media, and they are extremely durable. The 16-bit format is - to this day - considered a standard file format for the majority of applications. 16-bit 44.1kHz can be made to sound virtually indistinguishable from 24-bit to the majority of listeners thanks to technologies like noise-shaped dither, and technical advancements in recording technology.
If that's the case, then what is the point of high-resolution audio?
The point is that on a technical level, high-resolution audio formats are capable of producing a greater range and quality of sound than other current consumer formats, and that's a big deal. The new "Master Quality" designations will allow you to help differentiate standard resolution releases from *true* high resolution recordings, to a point. What's key, is that the content contained within the format can still be of low quality relative to the capabilities of the format. The delivery format a lens through which you hear the music, and ultimately the quality or resolution you hear will depend entirely upon how the recording was produced, and how much care was taken throughout each step of the production process to maintain quality.
By my suggested definitions at the top of this article, "high-resolution music" can transcend time and technology:
- It is entirely possible to create a low-resolution recording using PCM at 96kHz if the engineer chooses to use a low-grade recording chain, low-grade analog to digital converters or even using high-grade components but then deliberately adding modulation, noise or damaging transient details via post processing choices.
- It is entirely possible to create a recording using 1950s era analog equipment that contains a wider frequency range and dynamics than a modern-day recording. If the engineer carefully chooses their recording chain, and maintains as much quality as possible throughout the recording, mixing and mastering processes, they could easily create a higher resolution capture of a performance than someone who used modern equipment with less care and attention. You don't have to look far for examples of this.
Some music creators and publishers will therefore need to evolve their production practices to create more engaging recordings that contain much more of the dynamics and sound that high-resolution audio is capable of delivering. If they fail to do this, their music will not be competitive with other high-resolution releases. Creating "true" high resolution recordings and productions requires capturing the most pristine, and the most accurate (wide-bandwidth, high dynamic range) source signals at the moment of the performance, and maintaining that high standard of fidelity throughout the entire production process - including the final mastering stages.
At the same time, as consumers, we all need to educate ourselves a little bit, and that's where I hope this article has helped, some. For example, a high-resolution remaster of a 1960s analog recording may very well sound superior to the original vinyl or CD master that was made a few decades after the original release, but a high-resolution format cannot add fidelity that doesn't already exist in the source recording; it can only preserve the fidelity that is there to begin with. Any improvement in sound would depend upon the quality of the original source recording, and the mastering engineer who completed the remastering work - not the "high-resolution" format itself. The work may display an MQ-A label if the mastering engineer chose to master it to an analog medium before converting to high-res digital, or it may have an MQ-P, or MQ-D label if they decided that digital was more appropriate. The different "Master Quality" labels don't matter much from my perspective, and are more of a topic of interest for you, the consumer, to have a little more insight into the mastering process that was used for the high-resolution release.
My advice to all audiophiles and other music lovers is to explore new music, and look for those audiophile labels that are creating truly cutting-edge, truly "high-resolution" music, where they start with a great location, fill it with talented musicians playing incredible instruments, record an inspiring performance with the utmost fidelity, and then work very hard to preserve and enhance what was captured. Your ears will thank you for it! There are several audiophile labels around that are taking great care to create breathtakingly detailed recordings, and make them into productions that sound far superior to the average or mainstream music that is available today. If you are a music lover, it is well worth checking them out, and listening to what they have to offer.
To that end, the new high-resolution designations may even help spark the end of the "analog vs digital" debate for some, as more listeners hear what truly high-resolution digital recordings are capable of. Happy listening!