Popular Post mansr Posted January 15, 2020 Popular Post Share Posted January 15, 2020 The first "unfold" decodes compressed data hidden in the lower 8 bits of the 24-bit MQA stream. The output has twice the sample rate of the input. The second "unfold" is a trivial upsampling using one of 16 predefined filters as indicated in MQA metadata. We know how to decode this. There is no third "unfold." Anyone claiming otherwise is either a liar or repeating lies. semente, tmtomh, daverich4 and 1 other 3 1 Link to comment
mansr Posted January 16, 2020 Share Posted January 16, 2020 4 minutes ago, gmgraves said: So what you are saying, if I understand you properly, and I respect your knowledge, is that the Core Decode is really all one needs for MQA playback. That is correct. Link to comment
Popular Post mansr Posted January 16, 2020 Popular Post Share Posted January 16, 2020 3 hours ago, Norton said: Other than unpacking compressed data does the “first unfold” apply any proprietary DSP as well? In other words is there a reason why you might anticipate that it would sound different from a straight 24/96 file? In cases like this, it's useful to look at the encoder and decoder as a single black box. What comes out may well be somewhat different from what went in. How much of the processing resulting in that change happened in the encoder compared to the decoder isn't really relevant, though one can reasonably assume that the encoder is doing more work since it doesn't have to run on a puny XMOS processor. 3 hours ago, Norton said: I also note that some MQA files stay as “24/48” after the initial decode, what’s going on (or not going on) there? Simply put, you've been double-scammed. A lot of modern pop recordings are mixed and mastered in 24/44.1 or 24/48. The sane and honest thing to do would be to leave well enough alone and deliver these as plain FLAC. That wouldn't involve MQA though, so they've come up with a completely useless scheme whereby the encoder compresses the low 10 or so bits into 8 which are put into the bottom bits of the MQA stream. Above this they add some noise so the file played without a decoder becomes a little lower than CD quality. The decoder removes the noise and unpacks the compressed data, yielding a file that is almost as good as the original. In these cases, the FLAC-compressed MQA comes out a little larger than using FLAC directly without MQA. In short, MQA gives you lower quality at higher bit rate, then makes you pay for the privilege. semente, Norton, ShawnC and 4 others 5 2 Link to comment
Popular Post mansr Posted January 16, 2020 Popular Post Share Posted January 16, 2020 3 minutes ago, daverich4 said: For some reason I vaguely remember reading a long time ago in this thread that filters 9-16 are actually just duplicates of 1-8? Or, I could have just dreamt it. The value in the file is 5-bit number, so the possible range is 0-31. In practice, renderers only implement 16 filters, treating 16-31 as duplicates of 0-15. Examining various MQA files, I have only ever come across about half of those 16, and some are much more common than others. tmtomh and daverich4 2 Link to comment
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