MQA

Master Quality Authenticated (MQA) is a proprietary audio format.
It has been developed by Meridian Audio and launched in 2014.
Today MQA is an independent company.
 
MQA does three things.

  1. Watermarking
  2. Lossy compression of Highres recording
  3. Compensating for time-domain errors

Authenticated

There is a digital signature allowing the decoder to detect if this is the MQA file as it left the studio or not.

Compression

It compresses Highres audio into a 24 bit / 44.1 or 48 kHz PCM format.
As the result is PCM, it can be treated like any PCM format.
It can be contained in any lossless format like WAV, FLAC, ALAC, etc.


The lossy compression is rather complex.
It is based on the assumption that below -120 dBFS recordings contain random noise.
Compress the part above 44/48 and store this in the bits 20-24.

Audio Origami - Stereophile


As this space is limited, it is a lossy compression.

As the lower bits are used to store the compressed part, you won’t have the original 24 bit dynamic range. Its inventor claims a dynamic range of 17 bit.

The result is a 24 /44.1 or 48 kHz PCM audio file.
This can be played on any DAC with any media player.

The clever thing is that all what is stored below bit 16 appears as random noise.

 

To expand it to the original sample rate, a decoder is needed.
This can be implemented in software (media player) and/or in hardware (streamers).

Software is limited to what is called the first unfolding ( 88 / 96 kHz).
Only hardware not having a digital out is allowed to do the second unfolding (> 96 kHz).
This of course to prevent piracy.

Obvious you need a MQA enabled DAC to get the full result.

Time-domain

The other claim is that MQA can compensate for time-domain errors of both the AD converter used to make the recording and the DA converter used for playback.
This means that a DAC must be equipped with some additional hardware processing the audio and applying a specific algorithm tailor made for this specific DAC.
It implies that for each revision of the DAC, this as to be done anew.

 

The biggest advantage of MQA is probably the substantial compression of Highres.
If you run a streaming audio service like Tidal, Qobuz, etc.  it saves dramatically on bandwidth compared with streaming Hires in its original size.

The downside is of course as it is a proprietary protocol; somebody has to pay the license.

In the end this of course will be the consumer.

Problems

As with all new technologies, weird problems do occur.
TDCatTech found a gap in the frequency spectrum.

As Charles Hansen put it: MQA - More Questions than Answers.

MQA claims to be a lossy format saving bandwidth by throwing away data while maintaining perceptual transparency.
Exactly the same claim as made by MP3.
So MQA is highres MP3!

 

References

  1. High-Resolution Audio - A perspective - Bob Stuart
  2. Inside MQA - John Atkinson
  3. MQA (Master Quality Authenticated) Observations and The Big Picture... - Archimago's Musings
  4. MEASUREMENTS / IMPRESSIONS: Meridian Explorer2 Analogue Output - 24/192 PCM vs. Decoded MQA - Archimago's Musings
  5. IS MQA DOA? - John Siau - May 05, 2016
  6. MQA or "There and back again" - Jim Lesurf
  7. MQA and “Bit-Stacking” - Jim Lesurf
  8. MQA Time-domain Accuracy & Digital Audio Quality - Hugh Robjohns
  9. MQA & Tidal – where are we now? - John H. Darko
  10. Hypothesis Paper to support a deeper Technical Analysis of MQA (Master Quality Authenticated) by MQA Limited - Stephan Hotto
  11. On "blurring" and why MQA probably worsens transient smearing - Archimago's Musings
  12. Truncating MQA files to 16 bits and the blue light still shines - FredericV
  13. MQA: A Review of controversies, concerns, and cautions - Computer Audiophile
  14. MQA explained: Everything you need to know about high-res audio - Andrew Harrison - 5/2/2017