MQA software decoding in Roon

[erich6]

I am saying that the plot from MQA indicates that regardless of a file being decoded to 96, 192, or higher, the bandwidth is the same. There’s no more data required past 96KHz, which indicates that the rest is not original-data-driven but upsampling. That is the entirety of the argument. And quite frankly I don’t see anything in what MQA has said that categorically contradicts this.

I think the reason the bandwidth is the same in that plot is because it refers to a communication bandwidth, meaning the number of bits transmitted when delivering the digital (encoded/folded) MQA file in its FLAC container. A certain conclusion from these plots is that MQA compresses the original file such that the information in the music sampled at rates higher than 96kHz isn’t taking a lot of bits. You are inferring that because there aren’t many bits allocated to the high sampling rates that MQA actually stores no information captured by these sampling frequencies and it is simply “upsampling.” Based on the referenced provided on this thread and by the Roon team on MQA, I don’t think you are right. MQA is reconstructing the content originally sampled with high frequencies using an algorithm that decodes the original information content as close to the source analog signal as they can determine from the studio master (and its studio digitization.)

What I am saying is that you get to 352KHz by upsampling. I also said that the upsampling is possibly better informed than a generic upsampling by a little bit of data in the 96KHz PCM stream. For example it could chose on the aggressiveness of the min phase filter for upsampling - and I said that is not without value. But upsampling and reconstructing actual higher frequency information are two very different things.

Your description of upsampling is certainly valid but it isn’t what MQA is doing in the decoding as far as I can tell from what I’ve read.

I think one reason there is much confusion on the thread (and elsewhere) about this is because people equate higher sampling frequency with higher information content. That is simply not the case. High frequency information content does require high frequency sampling rates to properly capture the signal but just because a signal was sampled at 352kHz it doesn’t mean it has 352kHz worth of information. That is solely a function of the original analog signal (and actually, the true information content was the live music in the studio, it is all a representation after recording, mastering, etc.). The MQA approach is to put less focus on the sampling rates and more on the actual analog signal information content.