Now since there are MQA encoded FLAC test files available, I wanted to see how the file works out without MQA decoder - as a normal FLAC.
If we first look at the original 352.8/24 (DXD) file that has FLAC size of 69 MB:
We can see that there is content up to around 57 kHz.
If we then convert it to 44.1/24 we get a FLAC with size of 14 MB:
From the filter roll-off we can see that there's quite a bit less than 24-bit worth of information, amounting slightly less than 18-bit. Meaning about 108 dB SNR. Quite a lot of low level information visible.
OK, so how would this look like in normal 44.1/16 RedBook FLAC with size of 6.2 MB?
Now it has lost some low level information.
But how does 44.1/24 MQA encoded FLAC with size of 16 MB, decoded as normal file without MQA capability look like?
Whoops, there's significantly less than 16-bit worth of resolution left, with MQA data appearing as high frequency noise. Worse than RedBook format FLAC.
Next, I'm curious how big the file would be, if we optimally encode this content as FLAC? So we need 60 kHz of bandwidth and 18-bit worth of resolution. So let's go and encode it as 120/18 FLAC with size of 13 MB:
Perfect! Everything preserved, and the file is 3 MB smaller than the MQA encoded FLAC! Down size is now that you would need a player capable of upsampling this to a rate suitable for your DAC, for example HQPlayer.
Next let's try to encode it to a format that can be played on ordinary equipment/software, that is 176.4/18 FLAC, which ends up as 17 MB file:
This has about 30 kHz of unused bandwidth, but the file is only 6% larger than the MQA encoded and can be played on pretty much anything that can play hires FLACs and doesn't lose anything compared to the original while doing so.
We can also check how the result looks like at 96/18 FLAC with size of 12 MB:
Most of the content is preserved with highest harmonics cut out only of couple of strongest tones.
I did some listening comparisons between the MQA encoded file and the 120/18 FLAC, both played out at 24.576 MHz DSD rate to iFi iDSD Micro DAC, Fostex HP-A8C headphone amp and Sennheiser HD-800 headphones. And I preferred the 120/18 FLAC...