MQA and Devialet

[Jean-Marie]

I am wondering at which level MQA has to be implemented to take full advantage of its sound quality.
If Devialet can decode MQA fully at the processor level just before the DAC it should maintain everything of its promised quality. Considering the problems Devialet has with some digital issue like AIR I doubt we will see that soon but they could surprise us!
The other alternative is that some software like Roon can decode MQA (and not just the 44.1kHz core) on a computer or music sever. The problem will be that decoded stream has to be transmitted to a Devialet and will that preserve all the timing MQA claims to be so essential for prefect digital audio. So will USB etc mess it up?

I looked at the supporting patent and it appears that MQA is a lossy encoder and clever packaging that is backward compatible with a traditional PCM decoding.

In the patent, the input of the whole process is a 9kKHz PCM stream and the final output is an other 96 KHz PCM stream. So MQA can be decoded anywhere in the chain, the only requirement being to be able to transport the resulting PCM stream losslessly.

What MQA does it splitting the band between 0-24kHz and what is above. It is encoding losslessly the lower band using 13 bits and putting that in the MSB part of a 16 bits stream. They use the 3 remaining bits to encode in lossy manner what is above 24 kHz.

So basically they trade off a higher noise floor (-90 dB instead of -96) to be able to reconstruct approximately the higher band while fitting in the nitrate of 44kHz/16 bits PCM stream. The clever part is that if you take a traditional decoder, it will just take the 3 LSB as noise and will be able to deliver an almost CD quality output. An MQA decoder will be able to interpret the 3 LSBs.

What is important to keep in mind is that the output of MQA will always be lossy compared to the input PCM stream, but it will be much lower nitrate than the raw PCM. So it is a clever streaming container but nothing else, meaning that if your software on your PC or MAC or Dialog implements MQA in software and is feeding the Devialet using 96/24 or 192/24, you will get all the benefits of MQA.

Best regards,

Jean-Marie