Master Quality Authenticated

MQA logo

Master Quality Authenticated (MQA) is an audio codec intended for high fidelity digital audio internet streaming and file download.^[1] 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,^[2] although the concepts underpinning the development had previously been the subject of a presentation to the Audio Engineering Society British Section (10 June 2014)^[3] and a paper (published 8 October 2014) presented at the Audio Engineering Society 137th Convention in Los Angeles, CA in October 2014.^[4]

MQA was demonstrated to visitors to the Consumer Electronics Show in Las Vegas in January 2015.^[5] 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,^[6] with Warner Music Group announcing the signing of a "long-term licensing deal" with MQA at the Munich High End show in May 2016.^[7]

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'.^[8]

Codec description

MQA encoding is 'lossy';^[9] 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.^[10] MQA claims that the use of these novel sampling technologies may result in standard methods of analysing conventional digital audio content producing meaningless or misleading results when applied to MQA files.

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 legacy devices effectively to 13bit. MQA claims that nevertheless the quality is higher than "normal" 48/16, because of the novel sampling and convolution processes.

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, HDCD and aptX.

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".^[11] 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."^[12]

Some critical but primarily speculative comments have been made in online forums such as the Computer Audiophile forum^[13] 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.^[14]

Decoders

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, which allows a proper MQA file to be authenticated and the full quality of the signal decoded only on commercially-licensed equipment.

Further reading

• Treatise on technical aspects of MQA

References

Also see mp3PRO for MQA-like lossy codec that separates lower and higher frequencies