What is 16-bit MQA?

MQA Catalogue

We often use high sample-rate examples, such as 192kHz, to explain how MQA ‘Origami’ packs the recording into a more efficient form.
But the end-to-end system benefits of MQA are just as important when the sample rate is low.

This matters a great deal because the music catalogue includes many masters that were originally recorded and produced at 44.1kHz – and a high percentage of these only exist in 44.1kHz 16b (aka ‘Redbook’).

For this catalogue, which spans an era between 1977 and 2010, MQA can take us back much closer to the original studio sound – closer and more authentically than most ‘remastering’ releases (which add effects rather than subtract errors). In many cases the clearer sound brought by MQA is profound.

In the early years of digital, recording and production equipment was much less sophisticated than today. At one level this might be an advantage – less ‘messing with the recording’ between studio and release keeps it cleaner – but also early digital technology introduced systematic defects that we are able to detect and correct. (Some of this is described in our AES paper[1])

What is MQA 16b?

There are three ways we can end up with a 16-bit MQA file: 1) Encoding a 16b 44.1 (or 48) kHz master; 2) A derivative of a 24b MQA encoding; 3) A custom MQA-CD encoding.
In all three cases, the MQA files can deliver an audible dynamic range that exceeds 16b.

Some more detail on each type:

When MQA encodes a 16b 44.1kHz Master the resulting full MQA file is also 44.1kHz/16b. Despite being 16b, this file contains all the information for decoding and rendering. These MQA encodings also contain all of the information accessible when playing the original master and in some cases more.
If the original source is 44.1kHz/24b or if the sample rate is 88.2, 176.4, 352,8 kHz, or DSD, then a standard MQA file will be 44.1 kHz/24b. The file contains the information for decoding, ‘unfolding’, and rendering.
This 24b MQA file is structured so that, if in distribution it encounters a ’16-bit bottle-neck’ (e.g. in a wireless or automotive application), then the information in the top 16 bits is arranged to maximise the downstream sound quality and still permits unfolding and rendering. See [2]
So, we can encode high-rate masters and then truncate the MQA from 24 to 16 bits and still get a high measure of the possible sound quality (with or without a decoder). This MQA file can be sent over any 16-bit distribution system – including as a substitute for Redbook to streaming services and, interestingly, on a CD. Importantly, this 16-bit version of the MQA playback can be heard, proofed and authenticated as an approved rendering in the studio.
For this reason, some boutique labels no longer create Redbook files but chose the higher quality and authentication offered by the 16b MQA file.
In 2) above, an MQA 16-bit file was made by first optimally encoding to 24 bits and then removing the lower 8 bits. But if we know the file is only for MQA-CD, then the encoder uses different optimisations to squeeze even more from the CD.

Footnotes

[1] J. R. Stuart and P. G. Craven, “The Gentle Art of Dither,” J. Audio. Eng. Soc., vol. 67 (2019 May) Open access: DOI: https://doi.org/10.17743/jaes.2019.0011

[2] MQA-CD: Origami and the Last Mile