Listening to yet another new ‘saviour format’ for optical disc.
By Roy Gregory
Imagine the scene: all those file-replay advocates complacently basking in the assumed superiority of their technological solution when – BANG! Suddenly, MQA detonated loudly and rudely, right in their midst, like a hand grenade exploding in a picnic hamper. In no time at all, the orderly world of virtual music and bit perfect copying, CD fire-sales and unlimited musical access without leaving your listening seat had descended into an unseemly online brawl between MQA evangelists and those screaming “FOUL!” The ‘debate’ rumbles on, although in the manner of these things, it’s no nearer concluding. The situation wasn’t helped by distinctly underwhelming early presentations of MQA, or the strident claims made on its behalf.
So what are we to make of the relatively recent emergence of MQA encoding on CDs – and decoding in CD players? For whilst it’s easy enough to understand the attraction, even necessity of lossless compression systems for network file replay, their application to the fixed Redbook 16bit/44.1kHz format of CD is a less obvious requirement. In order to understand how and why MQA has any benefits to offer compact disc, it’s necessary to look first at the MQA process itself.
The story really starts with MLP – or Meridian Lossless Packaging –compression software that was developed by Meridian to help the storage of high-res files and their network replay. Cynics might suggest that the subsequent launch of MQA was an attempt to monetise the technology that had been given away free in the form of MLP, although MLP was actually licenced as part of the (effectively stillborn) DVD-Audio standard and was never open-source software. MQA claims to offers a superior and far more sophisticated solution than that earlier software – and it’s around those claims that the debate rages. According to its developers, MQA is both a compression system and a corrective algorithm, a system for counteracting inevitable timing errors induced in the Redbook and other digital encoding processes. It is important to appreciate that, in theory, MQA offers an end-to-end solution, from recording to replay. However, in practice (certainly currently) relatively few recordings are encoded directly into MQA. Instead, existing recordings – analogue or digital – are up-sampled (as required) and encoded, either as streamable/downloadable files or CDs. MQA’s aim is, of course, to achieve the same sort of studio penetration once enjoyed by Dolby noise reduction – with its consequent impact on domestic hardware.
Because identifying the error mechanisms of the original encoding process is critical to their correction, this is an important factor in how effective MQA’s corrective element can be. In practice, the vast majority of digital recordings were made using a relatively small range of A-to-D encoders, making it practical to calculate the error mechanisms involved for each. As long as you can identify the original encoder, you should be able to reverse engineer its digital fingerprint. The greater the information available and control over the digital encode/decode chain, the greater the potential benefit. That is not as fanciful or outlandish as it might seem. In fact, it bears some similarity to the thinking behind the Wadax DACs that are setting entirely new standards of digital performance, so that in itself should pique our interest. But working from an existing 44.1 or 88.2kHz digital file, in the absence of hard facts about its provenance, some measure of unidentified timing error has already been introduced, complicating the issue of correction. When playing discs, the provenance is indicated by the display of either MQA or MQA STUDIO, the latter indicating a superior degree of knowledge and/or control over the process as a whole. Can you hear the difference between MQA and MQA STUDIO? More on that later…