An Introduction into High Resolution and Master Quality Authenticated Audio – MQA.

A Little Historical Perspective

It all started in 1982 when Phillips and Sony released the compact disc or CD. This was the introduction of digital audio to the public. Those early discs sounded awful, despite being uncompressed, due to the digital technology and techniques used to create and replay them. How things have moved on from those early days when audio was sampled at 44.1KHz and converted to a 16 bit digital word. These discs were the first taste of real convenience for the public for listening to music, especially, as shortly after this CD release in 1984, Sony introduced a small portable CD player, the Discman.

While the portable CD player made listening to music so much more convenient, the digital technology behind this new storage technique rapidly moved on culminating, I suppose, in the development of the ubiquitous MP3 compression. Now you could squeeze hundreds of hours of music into a matchbox sized device that would run for hours on just one small battery. Convenience had become the word of the day, NOT QUALITY.

Fortunately, audiophiles continued to clammer for high quality audio, with a demand just sufficient enough, to keep vinyl barely alive, until its recent resurgence. This demand for high quality audio resulted in several manufacturers developing new methods of compressing audio into higher quality digital streams or no compression at all on plastic.

So entered a whole new dimension of techniques and technology that would allow public access to a wider range of audio qualities, from the original studio masters all the way down to MP3.

In parallel with these digital developments, the public moved online, and the web has now become one of the primary sources for the delivery of both audio and video digital files. With demand growing in leaps and bounds for web connectivity to be faster and cheaper, people didn’t want to wait or pay for long file downloads that consume both time and money. While at the same time,  there was a growing demand by music lovers to have better quality audio than can be served up by MP3 and other lossy compression formats.

Many digital audio file formats have been developed over the years, but until recently compression has been used in many of them in order to reduce the file size by throwing away digital audio information that SUPPOSEDLY the listener cannot hear! Streaming services such as Spotify supports Ogg Vorbis, and streams at 320Kbps, and Apple Music supports AAC files at 256Kbps. These data rates being but a small fraction of the uncompressed original data rate. No matter how well compression is applied to an audio signal, its effects on it are generally audible, given the correct listening environment and an ‘educated’ pair of ears.

A few terms & definitions;

• Lossy compression – a mathematical technique of reducing the original uncompressed digital bit rate of a signal, by discarding data (bits) that the ear finds difficult to detect or interrupt. (This threshold depends upon how ‘educated’ the listeners ears are and the technical quality of both the hardware and listening environment)
• Mathematically lossless compression – a method of reducing the original bit rate of a signal that allows for its bit for bit reconstruction of the original data by the receiving device. Do not assume that mathematically lossless means that the reconstructed signal is identical to the original master signal. Your DAC hardware has a big part in this!
• Uncompressed – a file transfer that replicates the original data bit for bit. Again, its reconstruction and reproduction is only as good as your hardware.

Note: Besides the compression of an audio signal there are many other factors that impact its final quality. Remember, we often have to convert the analog signal both to and from the digital world even if we are not using compression. For example, an uncompressed CD, or room equalization. This entire chain of digital processing, besides impacting dynamic range can also impact the frequency and time domain of the signal. Nothing is a simple as it seems!

Enter High Resolution Audio.

Hi-Res Audio

High-Resolution audio files offer significantly superior sound over compressed formats, even if slightly lossy. As bit rate tends to be king of quality (see comments below)  it is obvious that an MP3 file supporting only 320Kbps will not sound as good as a CD at 1411Kbps or a 24bit/192KHz file at 9216Kbps. These much higher bit rates that do not ‘throw away’ audio information, maintain the full dynamic and frequency range of the original recording, while also maintaining the correct time domain information. This results in the listener being brought closer to the original performance that the studio engineer heard in the control room or at the concert.

Until recently, Hi -Res audio standards were not dictated by any professional bodies, unlike SD, HD and UHD video standards. So in the case of audio, everybody can have their own standards, and many still do. However, in 2014 The Digital Entertainment Group, Consumer Electronics Association and The Recording Academy reached an agreement with record labels as to what defines Hi-Res Audio. This agreement was fully supported by large companies like Sony Music Entertainment, Universal Music Group and Warner Music Group.

High-resolution or Master Quality (MQ) audio being defined as “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.” The agreement supports four categories that are used to create a Master Quality recording:

• MQ-P – from a PCM master source – 48kHz/20bit or higher – typically 96/24 or 192/24 content
• MQ-A – from an analogue master source
• MQ-C – from a CD master source – 44.1kHz/16bit
• MQ-D – from a DSD/DSF master source – typically 2.8MHz or 5.6MHz content

In further support of these standards the Recording Industry Association of America (RIAA), in 2015, issued a logo that should show up on every track and album that can be classed as hi-res audio.

Generally speaking it is the sample rate and and how many bits that the sample is converted to that has the largest impact on the sound quality. So high sample rates and long word lengths like 196KHz/24bit will provide higher quality audio than highly compressed MP3. Unfortunately, these two parameters are only an indication as to just how good the audio will sound, as many other factors will affect what eventually leaves yours speakers or earphones. So, excluding your amplifier and speakers, these would include:

• Original source quality – see above MQ classifications
• Compression algorithm – type of compression and how much bit rate reduction is applied
• Analog to digital conversion (ADC) at the source
• Digital to anlog conversion (DAC) at the destination
• Filter performance for both the ADC and DAC process
• Clock jitter – how stable in time the bits of data are moved through the digital system
• Circuit noise levels – created from both digital data and analog electronics
• Crosstalk – between audio channels

As can be seen above there is a lot to get right if the original studio quality sound has any chance of making it to your speakers (or headphones).

Two very popular methods of encoding to Hi-Res files are the Free Lossless Audio Codec (FLAC) and Apple Lossless Audio Codec (ALAC).

Other popular file formats would include Wave (WAV), Audio Interchange File Format (AIFF) and Direct Stream Digital (DSD). Though companies like Meridian and Linn also have there own lossless codecs, Meridian Lossless and Studio Master FLAC respectively.

There are now many locations where these Hi-Res files may be purchased, to include:

• HDTracks
• 7Digital
• Naim Label
• Linn Records
• Bowers & Wilkins Society of Sound
• Qobuz
• Technics Tracks
• Onkyo Music
• Primephonic

Several studios with large music catalogs like Universal, Warner and Sony are also offering their catalogs as avilable Hi-Res downloads.

So now we have high resolution audio standards (well sort of) and file types that can be downloaded and provide excellent audio quality . The problem with these files is that they are large and take time to download and consume a lot of storage space on portable devices. With the advent of Cloud storage and higher bandwidth connections, together with lower connection charges, there is no longer a need to keep all your music stored on your personal device.

Enter music streaming.

Hi-Resolution Audio Streaming

Music streaming has now become the main service through which most of us (not me) listen to our music, including music streaming over your home network. Dollar for dollar, it now exceeds the sales of the physical media Vinyl and CD combined.

Lower quality compressed music files are relatively easy to stream as they do not require high bit rates, and until recently, streaming these higher quality compressed audio formats was demanding on data connections particularly to smartphones and, of course, their storage space.

There are now an ever growing number of streaming services to include:

So in the search to find a method of delivering Hi-Res studio quality audio to the home and mobile device, as a streamed file format, at relatively low bit rates, and file size, enter MQA.

MQA – The Technology

MQA stands for Master Quality Authenticated – this audio technology was developed by Bob Stuart, co-founder of Meridian Audio and is the CODEC (coder/decoder) that makes high resolution streaming now a reality.

MQA claims that its processed track data uses very similar bandwidths to those used by streaming standard CD tracks. So if you can stream CD tracks, you will most probably be ably to stream MQA encoded tracks. This means hi-res audio streaming is now possible, with songs being delivered to the listener almost exactly how they were recorded in the studio, without requiring huge amounts of bandwidth.

Remember that MQA IS NOT LOSSLESS. It is just not very lossy. It uses some very clever signal processing techniques to squeeze a higher quality signal into a lower streaming bit rate.

This is not a new file type that adds to the myriad of existing wrappers like FLAC and ALAC. MQA files are packaged inside any lossless container such as FLAC, WAV or even ALAC. In order to decode the almost lossless versions of this file you will need compatible hardware and software or a desktop app from the streaming service.

This development has already managed to get many hardware manufactures on board to support the format, including:

• Oppo
• Sony
• Pioneer
• Onkyo
• NAD
• Meridian
• Audiolab
• Mark Levinson
• LG
• Technics
• Bluesound
• Moon
• Simaudio

The list just keeps growing, and many existing items of hardware can be upgraded with just software to support at least part of this new standard.

So What Makes MQA different?

In simple terms this new file format is a bit like a Matryoshka or Russian Nesting Doll. The file data structure is composed of three layers, which could be considered to be folded in on each other with bit depths between 13 and 24 bits. The bits beyond 17 are used to carry the additional data used to create what is a virtually lossless signal, provided that the data in the ‘touch up’ channel never overloads. The resulting file can be carried by any lossless wrapper like FLAC.

• Layer 1 -lossy
  • No MQA or an Authenticated decoder -Equivalent (or better) audio quality to a CD, with a sample rate of 44.1KHz or 48KHz and a bit depth up to 16. This file can be played back by any conventional DAC.
• Layer 2 – almost lossless
  • MQA core decoder -Equivalent to playback at 88.2KHz or 96KHz with a bit depth of up to 24.
• Layer 3 – virtually lossless
  • Full MQA Decoder with stream authentication unfolds the last layer of data and manages the DACs performance to provide the highest audio quality possible that this technique can support; 24 bits up to 768KHz, currently 352.8KHz @ 24 bit.

So depending upon the performance of your hardware and software and, of course, how much you pay, you can access the base layer 1 for CD quality, layer 1 and 2 for high resolution almost lossless audio, or layers 1, 2 and 3 which provides you with audio quality approaching that heard from the original master tapes or source. The decoding is a transparent process to the user, as the playback hardware and software recognizes which layers it can handle, and adjusts the playback quality automatically.

All of this functionality being combined in a bit rate of approximately 1.5Mb/s, not much greater than the 1.411Mbps of an uncompressed CD sampled at 44.1KHz with a 16 bit sample word.

So Where Can you Download MQA Music?

MQA music files are now available from a growing number of sources, to include:

• Tidal (Masters)
• Major music labels such as:
  • Universal
  • Warner Bros
  • Sony Music
• Merlin
• Highresaudio
• Onkyo Music
• Deezer
• HDTracks

My 2 Cents

So yes,  for those of you who stream their music to their smartphones or store it on their computers etc., MQA is a great improvement on what you have had in the past. The need for MQA on a smart phone, any smartphone, listened to through ANY pair of headphones, defies my understanding, and to me is an oxymoron. It certainly makes more sense for residential streaming, but what’s wrong with playing the physical media and having NO compression? Is everybody now so busy, that they can’t change a CD or sit down and listen to a vinyl track? Is all this music, which took performers and engineers hundreds of hours to meticulously produce and record, just becoming elevator music? A background of noise that fills in those silent periods between gaming and work?

Despite all the apparent advantages of this new audio format, my music room is, and will remain, a compression free zone, and I don’t just mean lossless free!

Sit down, relax and LISTEN to your uncompressed music. You will be amazed how much better you will feel afterwards. The touch of vinyl and plastic media, almost sensual!

Happy streaming.

See my update on MQA using the Oppo 205 USBDAC and Tidal Streaming.