Master Quality Authenticated

MQA logo

Master Quality Authenticated (MQA) is an audio codec using lossy compression^[1] and a form of file fingerprinting, intended for high fidelity digital audio internet streaming and file download.^[2] Launched in 2014 by Meridian Audio, it is now owned and licensed by MQA Ltd.

History

Announcement of MQA was made on 4 December 2014 at a launch held at The Shard in London,^[3] although the concepts underpinning the development had previously been the subject of a presentation to the Audio Engineering Society British Section (10 June 2014)^[4] and a paper (published 8 October 2014) presented at the Audio Engineering Society 137th Convention in Los Angeles, CA in October 2014.^[5]

MQA was demonstrated to visitors to the Consumer Electronics Show in Las Vegas in January 2015.^[6] Several download/streaming services, playback system manufacturers and record labels have subsequently announced support for the technology, including Pioneer Corporation, Onkyo, Meridian Audio, 7digital, Norwegian label Lindberg Lyd (2L), Mytek and others,^[7] with Warner Music Group announcing the signing of a "long-term licensing deal" with MQA at the Munich High End show in May 2016.^[8]

In May 2016, the Recording Industry Association of America (RIAA), in cooperation with the Recording Academy Producers & Engineers Wing, the American Association of Independent Music (A2IM), and DEG: The Digital Entertainment Group, announced that services providing music encoded in MQA are eligible to carry the industry's official logo mark for "Hi-Res MUSIC".^[9]

Codec description

MQA encoding is lossy;^[10] it hierarchically compresses the relatively little energy in the higher frequency bands into data streams that are embedded in the lower frequency bands using proprietary dithering techniques.

After a series of such manipulations, the resulting 44 kHz data, the layered data streams, and a final "touchup" stream (compressed difference between the lossy signal from unpacking all layers and the original) are provided to the playback device. Given the low amount of energy expected in higher frequencies, and using only 1 extra frequency band layer (upper 44 kHz band of 96/24 packed into dither of 48/16) and one touchup stream (compressed difference between original 96/24 and 48/16) are together distributed as a 48/24 stream, of which 48/16 bit-decimated part can be played by normal 48/16 playback equipment.

One more difference to standard formats is the sampling process. The audio stream is sampled and convolved with a triangle function, and interpolated later during playback. The techniques employed, including the sampling of signals with a finite rate of innovation, were developed by a number of researchers over the preceding decade, including Pier Luigi Dragotti and others.^[11][12]

MQA-encoded content can be carried via any lossless file format such as FLAC or ALAC; hence, it can be played back on systems either with or without an MQA decoder. In the latter case, the resulting audio has easily identifiable high-frequency noise occupying 3 LSB bits, thus limiting playback on non-MQA devices effectively to 13bit. MQA claims that nevertheless the quality is higher than "normal" 48/16, because of the novel sampling and convolution processes.^[13]

Other than the sampling and convolution methods, which were not explained by MQA in detail, the encoding process is similar to that used in XRCD and HDCD.

However, unlike other lossy compression formats like MP3 and WMA, the lossy encoding method of MQA is similar to aptX, LDAC and WavPack Hybrid Lossy, which uses time-domain ADPCM and bitrate reduction instead of perceptual encoding based on psychoacoustic models.

Reception

While the technology has received little comment in the general and mainstream press, it has been exalted by the audiophile and hi-fi press. Robert Harley, editor of The Absolute Sound has referred to it as "The most significant audio technology of my lifetime".^[14] Editor John Atkinson writing in Stereophile magazine following the UK launch in December 2014 wrote "In almost 40 years of attending audio press events, only rarely have I come away feeling that I was present at the birth of a new world."^[15]

Criticism

MQA has received criticism from various sources within the music industry.

Audio product manufacturer Schiit Audio announced that it will not be supporting MQA due to, amongst other reasons, the understanding that “…supporting MQA means handing over the entire recording industry to an external standards organization.”^[16]

In a blog post title “MQA is Bad for Music. Here’s why"^[17] Hi-fi Manufacturer Linn Products criticises MQA’s licensing requirements, asserting that MQA is "...an attempt to control and extract revenue from every part of the supply chain, and not just over content that they hold the rights for.”^[17] Linn conclude that as a consumer you will "…pay a higher price for the same music, and you’ll pay more for your hi-fi system too. And even if you don’t buy into MQA, everyone will get less innovation, creativity and poorer music as a result."^[17]

In an interview for online publication Positive Feedback, engineer Andreas Koch is critical of MQA due to its lossy algorithms and compression, along with its licensing requirements; also saying that a format such as this "does not solve any problem that the world currently has."^[18] Koch was involved in the creation of the Super Audio CD, the development of the Direct Stream Digital codec, and is co-founder of audio product manufacturer Playback Designs.

An article titled Digital Done Wrong^[19] on the International Audio/Video Review web site, concluded that MQA is founded on a fundamentally unsound understanding of correct digital audio processing and found that playback of a sample MQA encoding demonstrated gross distortion and reconstruction failure. It did however comment that some listeners may find the technical defects of MQA encoding subjectively pleasing.

Some critical comments have been made in online forums such as the Computer Audiophile forum^[20] and in audio magazine website comments, and a few writers have expressed concern in some areas. Over 80 detailed questions, some of which voiced these concerns, were submitted to the editors of the Computer Audiophile forum and subsequently addressed in detail by the creator of MQA, Bob Stuart, in an extended question-and-answer article.^[21]

Hardware and software decoders

Hardware decoders are manufactured by Pioneer, Onkyo, Mytek, Meridian, Cocktailaudio and Bluesound. Selected Meridian products will support MQA thanks to a firmware update. On software side, the desktop application by Tidal supports MQA.^[22]

Commercial MQA-capable playback devices require payment of a royalty to MQA Ltd per unit sold. Based on information from Auralic, a manufacturer of Audiophile Wireless Audio Streamers, Meridian Audio prohibits digital output of unpacked MQA in any digital format, only allowing the unpacked data to be fed to an on-board MQA-compatible DAC and output in analog form. Some claim this to be a part of DRM process^[13], which allows a proper MQA file to be authenticated and the full quality of the signal decoded only on commercially licensed equipment.

Streaming services

Starting in January 2017, Tidal provides MQA audio to subscribers of the Tidal "HiFi" package.^[23]

References

Further reading

• Treatise on technical aspects of MQA