Bandsplitting is supposed to be practically lossless - ie below your playback equipment's ability to reveal it to you.
And slow filters absolutely trade of frequency for time. That is the whole equation.
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MQA Deep Dive - I published music on tidal to test MQA
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And slow filters absolutely trade of frequency for time. That is the whole equation.
No, I think the patent is quite clear on this: it’s mathematically lossless.
Prove it!
I think the better analogy is with the UMG watermark (fortunately abandoned a couple of years ago). It isn't copy protection but can be a way to identify copies made from an original.
Please read warner's explainer on PFM. Best I have read.
Trade off between time domain and frequency domain performance has been understood for decades.
How abandoned tech applies here?
Got any link? Even a verbatim search on “PFM” “Warner” and “audio” does not yield anything useful
I'm talking about the concept. MQA encoding as a watermark.
SoundAndMotion
Active Member
Try “pink fish” and “werner”. Haven’t looked, so no link.
PFM is Pink Fish Media, an audio forum based in the UK. He is talking about some thread or post on that forum.
The steeper the FIR filter the more taps you need, the longer your impulse response is..
You need proof for that?
SoundAndMotion
Active Member
I know and he misspelled werner
So? That does not prove a thing..
So you guys expect me to go and find some post on some audio forum somebody made (among possibly thousands of other posts)
SoundAndMotion
Active Member
It seems I am confused what you want to be proven... Can you elaborate ?
Simple proof: Listen to the attached files.
Suppose we are downsampling a file to 12kHz sample rate, then the file should be filtered in a way that there is no content >= 6kHz before decimation. Due to the low 12kHz sample rate, everyone must be able to hear a faint tone in the attached "impulse long linear.wav" and "impulse long minimum.wav", but not in "impulse short linear legal.wav" and "impulse short linear illegal.wav".
"impulse short linear illegal.wav" is named as such because the stopband is >= 6kHz before decimation. After decimated, aliasing will occur down to about 5kHz. I aware that some people tend to use imaging and aliasing interchangeably, it can cause confusion, so here is an explanation:
https://www.audiosciencereview.com/...u-m4-audio-interface-review.15757/post-504008
However, 44.1kHz sample rate is the lowest norm for music distribution, so people needed to be able hear the same effect at around 22kHz, and the audio content itself also need to contain strong signal at this frequency region. Also, the "long" files can only happen on something like a chord DAC, for typical DAC chips, the "short" files are the norm.
Therefore it is all about frequency domain.
In the case that anyone interested in trying these things out with real music rather than an impulse, @KSTR provided an interesting listening test here:
https://www.audiosciencereview.com/...ike-if-we-were-bats-listening-examples.23776/
Suppose we are downsampling a file to 12kHz sample rate, then the file should be filtered in a way that there is no content >= 6kHz before decimation. Due to the low 12kHz sample rate, everyone must be able to hear a faint tone in the attached "impulse long linear.wav" and "impulse long minimum.wav", but not in "impulse short linear legal.wav" and "impulse short linear illegal.wav".
"impulse short linear illegal.wav" is named as such because the stopband is >= 6kHz before decimation. After decimated, aliasing will occur down to about 5kHz. I aware that some people tend to use imaging and aliasing interchangeably, it can cause confusion, so here is an explanation:
https://www.audiosciencereview.com/...u-m4-audio-interface-review.15757/post-504008
However, 44.1kHz sample rate is the lowest norm for music distribution, so people needed to be able hear the same effect at around 22kHz, and the audio content itself also need to contain strong signal at this frequency region. Also, the "long" files can only happen on something like a chord DAC, for typical DAC chips, the "short" files are the norm.
Therefore it is all about frequency domain.
In the case that anyone interested in trying these things out with real music rather than an impulse, @KSTR provided an interesting listening test here:
https://www.audiosciencereview.com/...ike-if-we-were-bats-listening-examples.23776/
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Hi all,
there has been much discussion about hurting the MQA requirements by test signals.
So I have prep'd a 24/96 (TPDF dithered) test track which I would first love to get encoded to MQA and second to see the decoded result as PCM.
The track should not exceed the MQA requirements (e.g. level at 24 kHz < -48 dB). If yes I can easily correct this.
As the content is clearly mathematically specified differences of the decoded PCM will tell more about the MQA quality.
Anyway I fear there will be no MQA authorized facility preparing an MQA encoded track.
So if in the future someone has a chance to get encoded tracks he may use this example and even include in in another track.
The track duration is 43.2 seconds (4194304 = 2^22 samples). The FFT plot in comparison to the MQA triangle (-2db/kHz slope) is in linear view:
With logarithmic frequency axis:
Listening to the track is possible, but as it is a test track it does not sound like music.
The test track can be downloaded by www.audiovero.de/freedownload/MQA_Triangle_Test96.flac
Have fun!
there has been much discussion about hurting the MQA requirements by test signals.
So I have prep'd a 24/96 (TPDF dithered) test track which I would first love to get encoded to MQA and second to see the decoded result as PCM.
The track should not exceed the MQA requirements (e.g. level at 24 kHz < -48 dB). If yes I can easily correct this.
As the content is clearly mathematically specified differences of the decoded PCM will tell more about the MQA quality.
Anyway I fear there will be no MQA authorized facility preparing an MQA encoded track.
So if in the future someone has a chance to get encoded tracks he may use this example and even include in in another track.
The track duration is 43.2 seconds (4194304 = 2^22 samples). The FFT plot in comparison to the MQA triangle (-2db/kHz slope) is in linear view:
With logarithmic frequency axis:
Listening to the track is possible, but as it is a test track it does not sound like music.
The test track can be downloaded by www.audiovero.de/freedownload/MQA_Triangle_Test96.flac
Have fun!
If you look at the .csv list of MQA albums on Tidal, there are quite a few made from 24/44. It would be interesting to check a few tracks from these and see if the ultrasonics are missing or if the decoded files have the fake mirroring. If you don't want to do it maybe I'll try to get another Tidal trial.
danadam
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Left and right channel, most probably.
As far as I understand, the first one is a spectrum of the whole one minute and the second one is an instantaneous (or whatever time window the program is using) spectrum at some point.
@amirm and others: I captured the decoded MQA of the Bruno Mars track and I get the same gapped and mirrored spectrum that Archimago showed. Can someone else do this to see what you get? If I'm doing something wrong I'd like to know about it. I checked a 2L capture against what @mansr got from the Bluesound decode and those are matching.
The DMCA refers to content "access controls." That has to be determined by a court.
So if Warner and MQA got together and decided they wanted to sue someone who used an alternative decoder which was used on Warner's music, unless case law exists that could easily be used to squash the suit, the person who created the decoder would need $150K or more to go to court to fight that it was not a violation.
This has long been an issue with the DMCA, that it is used by corporations against individuals who simply can't afford to fight for their rights.
So this is why you really need to talk to a lawyer when it comes to things like this, rather than having lay people assert their opinions as fact, as someone needs to know the case law to tell you if the DMCA might be used here.
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