MQA now live on Tidal

[watchnerd]

No, but there could be MQA CDs. There is a 16-bit version of MQA in the specs. It still allows for the folded higher sampling rate versions stored in the ultrasonic noise.

What ultrasonic noise would that be?

Redbook cuts off at 22khz.

 

[Werner]

My understanding is that the Tidal Desktop Client (the only way it works), does the first unfold.

This is correct.

Contrary to the earlier plans, quoted above, which banned the existence of a user-accessible digital stream of (partially) decoded MQA, it is now OK to do the first (origami) unfolding in software for output over a digital interface. The first manifestation of this was in the Blue Sound Node 2, whose SPDIF output was found to run at 2x when playing an MQA file. Back then it was not sure if this was intended. Now with Tidal doing the same it is clear that the MQA corporation compromised a bit on their original stance. Which is of course good. If only such first-stage decoders would be made public for use in the numerous Linux-based audio players out there...

Incidentially, people at CA have isolated the Blue Sound software decoder and are now using it for analysis.

What it doesn't seem to do is the second unfold where the origami algorithm is supposed to 're-imagine' the higher frequencies and restore them.

Terminology error. The 'origami' concerns the first fold/unfold (between 2x and 1x rates). Anything going higher than 2x on playback is the result of MQA-specified short-filter upsampling, with the generation of copious imaging components. Not folding. No origami.

 

[Don Hills]

Edit: Beaten to it.

 

[Fitzcaraldo215]

What ultrasonic noise would that be?

Redbook cuts off at 22khz.

Ultrasonic is not the right word. My bad. That implies an in audibly high frequency. I meant something like inaudibility low levels in the least significant bits. I think it is possible to envision that with 16-bit RBCD in a 24-bit MQA carrier. But, I do not hold out much hope for it in a 16-bit MQA carrier.

 

[Ken Newton]

Ultrasonic is not the right word. My bad. That implies an in audibly high frequency. I meant something like inaudibility low levels in the least significant bits. I think it is possible to envision that with 16-bit RBCD in a 24-bit MQA carrier. But, I do not hold out much hope for it in a 16-bit MQA carrier.

It seems to me that the Redbook compatible version of MQA probably would sound subjectively close to the 24-bit version. It was reported by 'Blumlein 88 'upthread that within a 16-bit Redbook container LSB bits 13 to 16 hold the MQA folded bands, which, of course, means that the primary band (Region A) has only 12-bits of native resolution available. However, for non-MQA Redbook playback, those 4 MQA bits would act as strong dither, improving the apparent channel resolution to below the dither noise floor.

As for those MQA bits representing the folded ultrasonic bands, 4 bits of resolution seems plenty for their purpose. Since they represent only ultrasonic content, the ultrasonic bands are not directly audible in themselves. They can, however, effectively hold the extra bandwidth needed to encode the original signal utilizing a slow roll off (time domain optimized) anti-alias filter without suffering alias products. The ultrasonic regions seem are likely captured primarily to provide wide transition band space for the slow anti-alias filter to reach it's stop band, not for the purpose of directly capturing musical information there. At least, that's my presumption.