DARKO: MQA: a non-hostile takeover?

[crenca]

Which of the numerous Dolby technologies are you referring to?

 

Well, I am only very vaguely familiar with Dolby so I can't in any way claim to be specific (or accurate - this could be a moot comparison), but I was thinking of "B" (or is it "C") that was the "tape hiss" one (discussed upstream). What the more modern "digital" Dolby (and DTS, etc.) are doing beyond being a kind of meta format/template for surround I really have no idea...

[crenca]

We know from the patents that it dithers the input to 17 bits.

 

I wonder why this is not talked about more? Is that not VERY significant from a SQ point of view? It seems to me it is given what I understand (which might be mistaken) about what dithering does in digital audio.

 

It's possible that this initial processing also includes a slight boost to low-level signals, i.e. compressing the dynamic range a little. This would certainly result in background "details" becoming more easily heard.

 

Now that a few DAC firmware updates with MQA are available, perhaps someone will be able to reverse engineer the decoder and find out what it's really doing. Of course that still won't tell us how the encoder works in detail.

 

Do professional (or even amateur) sound engineers have access to tools that would enable a DSP compressing/boasting of only low level signals (relative to all other signals) to see what the effect would be?

[mansr]

Well, I am only very vaguely familiar with Dolby so I can't in any way claim to be specific (or accurate - this could be a moot comparison), but I was thinking of "B" (or is it "C") that was the "tape hiss" one (discussed upstream). What the more modern "digital" Dolby (and DTS, etc.) are doing beyond being a kind of meta format/template for surround I really have no idea...

 

The old Dolby noise-reduction works by doing a dynamic compression of the signal bringing more of it above the tape noise floor. On playback, the signal is expanded again which pushes the noise floor down and restores the original signal. The exact filters used are probably not (supposed to be) widely known.

 

Digital Dolby surround was initially a lossy codec, later expanded with lossless modes and various other enhancements. Most of it is public by virtue of being part of the ATSC A/52 and ETSI DVB specs for digital TV which are free to download. They still make money off it by selling software as well as through patent and logo licensing programmes.

[Rt66indierock]

Steve Stone tried to show what I said was false and failed. And I haven't said anything that can't documented elsewhere.

[Rt66indierock]

It is not readily apparent on the early CD I own. And not either the Hi-Res or MQA versions I listened to at T.H.E. Show. Sorry but only the early seventies pressings have it that I know about. And remember I've speculated the master was damaged. See comments about the surround sound versions which tend to support this but aren't definitive.

[tailspn]

Do professional (or even amateur) sound engineers have access to tools that would enable a DSP compressing/boasting of only low level signals (relative to all other signals) to see what the effect would be?

 

Sure, it's called compression, where you can select the point in the dynamic range to expand, and by how much. It's a very often used post process to compress or maintain the total dynamic range while expanding the lowest levels. Without it, no car audio would work with the low level signals being washed out by the ambient noise, while the highest levels distroy your hearing. It's also the mechanism used in the loudness wars.

[crenca]

Sure, it's called compression, where you can select the point in the dynamic range to expand, and by how much. It's a very often used post process to compress or maintain the total dynamic range while expanding the lowest levels. Without it, no car audio would work with the low level signals being washed out by the ambient noise, while the highest levels distroy your hearing. It's also the mechanism used in the loudness wars.

 

I thought so. Is there any evidence (either way - or is there simply no evidence) that this is what Steven Stone is or could be hearing? He does his own recordings, so he must have experience with this and one would think that he would be able to note the difference between what MQA is doing and common run-of-the-mill compression (which would seem to invalidate mansr suggestion)...

[crenca]

Steve Stone tried to show what I said was false and failed. And I haven't said anything that can't documented elsewhere.

 

You lost me here Rt66indierock - was Steven Stone part of that thread over at Stereophile?

[tailspn]

Mansr is correct; Dolby noise reduction is not compression per se. It's a two step process, like vinyl equalization, to expand/compress certain frequencies pressed into a record, then the reversed at playback to yield the original audio...kinda.

 

Compression is used to alter the normal/original dynamic range by pulling the bottom of the dynamic range up, leaving the top (loudest) alone.

[Rt66indierock]

You lost me here Rt66indierock - was Steven Stone part of that thread over at Stereophile?

 

Separate on his site.

[esldude]

Now that I think more about this, haven't all technology changes in recording and delivering music to the public changed the sound? Albums released on vinyl back in the day had to be mastered for this medium (and still do today). Maybe it's the same as MQA, the material should be mastered for this technology. Just an idea.

 

Yes, I wouldn't hold that against MQA. It was this thing that made so many of the very early CD transfers sound bad. People had to adapt to the performance envelope of a new technology.

[esldude]

From Steven Stone in the TAS article

Magic? Voodoo? Not really, if you understand the basics and weaknesses of digital recording.

 

snippage

 

Simultaneously, but separately, MQA uses advanced sampling and playback methods that particularly stabilize low-level signals and the recording ‘noise-floor.’ This uses advanced insights from sampling theory and neuroscience.” MQA removes the distortions that were added during the recording process.

 

If you have a digital recording device that uses an analog-to-digital converter, try this test: Record something at maximum levels that peak just below 0dB, and then record the same track at the lowest settings possible. The lower-level recording will have far more additive distortion than the higher-level one. Even when a recording is done at correct volume levels the quiet passages and accompanying background noise will inevitably have higher levels of distortion than the loudest sections. This is not debatable—it’s science. If you can reduce these low-level additive distortions the results will be a better-sounding recording. It is really that simple.

 

Say what? I will grant him what he said he heard with his own recordings. The above seems like his imagination trying to make an explanation. MQA now stabilizes low level signals and the recording "noise floor"? Then what is he claiming about his suggestion to test it yourself with recordings at high level vs low levels? Like other mediums any distortion of low level sounds will simply fall well below the noise floor. One can record at surprisingly low levels in digital and amp it up to hear reasonably clean renditions at levels that would leave tape simply losing all the music. This is one of those cases of a writer trying to simplify explaining what something sounds like and spreading misinformation in the process. Digital recording and playback is limited by the base level noise in all other parts of the system.

 

There would be no point in a Dolby-esque noise reduction system. The basic digital medium already exceeds thermal noise in the electronics. I don't see that MQA even claims to aid such matters. There is the provision to have pre-emphasized redbook with de-emphasis on the playback end. I do believe it was Bob Stuart who developed that. As I recall that worked something like RIAA or Dolby and allowed effectively something like 19 bit resolution in the range where our hearing was most sensitive (2-5 khz) over the 16 bit redbook medium. It made more sense than the Keith Johnson system later marketed. With 24 bit digital we don't benefit from either of those things.

[Tony Lauck]

From Steven Stone in the TAS article

Magic? Voodoo? Not really, if you understand the basics and weaknesses of digital recording.

 

snippage

 

Simultaneously, but separately, MQA uses advanced sampling and playback methods that particularly stabilize low-level signals and the recording ‘noise-floor.’ This uses advanced insights from sampling theory and neuroscience.” MQA removes the distortions that were added during the recording process.

 

If you have a digital recording device that uses an analog-to-digital converter, try this test: Record something at maximum levels that peak just below 0dB, and then record the same track at the lowest settings possible. The lower-level recording will have far more additive distortion than the higher-level one. Even when a recording is done at correct volume levels the quiet passages and accompanying background noise will inevitably have higher levels of distortion than the loudest sections. This is not debatable—it’s science. If you can reduce these low-level additive distortions the results will be a better-sounding recording. It is really that simple.

 

Say what? I will grant him what he said he heard with his own recordings. The above seems like his imagination trying to make an explanation. MQA now stabilizes low level signals and the recording "noise floor"? Then what is he claiming about his suggestion to test it yourself with recordings at high level vs low levels? Like other mediums any distortion of low level sounds will simply fall well below the noise floor. One can record at surprisingly low levels in digital and amp it up to hear reasonably clean renditions at levels that would leave tape simply losing all the music. This is one of those cases of a writer trying to simplify explaining what something sounds like and spreading misinformation in the process. Digital recording and playback is limited by the base level noise in all other parts of the system.

 

Low level digital signals are not distorted provided that the original analog to digital conversion and any subsequent reductions in bit depth (e.g. 24 to 16 bits) are properly dithered. This is true theoretically and it can be verified practically by anyone with digital workstation software. There will be no distortion even if the audio signal is reduced in level so that there is only 8 bits of resolution, although in this case the result will have a lot of hiss.

 

 

Game over for Stephen Stone. He either doesn't know what he is talking about or he is acting as a paid shill.

[semente]

Now that I think more about this, haven't all technology changes in recording and delivering music to the public changed the sound? Albums released on vinyl back in the day had to be mastered for this medium (and still do today). Maybe it's the same as MQA, the material should be mastered for this technology. Just an idea.

 

A remastered version of The Beatles' Live at Hollywood Bowl will be launched this weekend.

I was listening to the story in the car this morning on Radio 4, where the engineer described the processes of toning down the awful hysteria, which included EQ the upper mids and highs to bring the drum kit and vocals up; a change in timbre on vocals was obvious even in the short before and after.

 

R