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#401875 - 03/13/14 12:45 AM Re: Sounded like Neal had a great idea until... [Re: Murph]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
The biggest problem with MP3s in the beginning was the imperfect psychoacoustic modeling. While it may not be computationally possible to build a perfect model of human hearing, things have improved dramatically since those early days. So yeah, MP3s (and other lossy encoding schemes) throw away four-fifths (or more) of the data, but it's stuff your brain can't pick out anyway.

The other part of the encoding, storing the data as cosine coeffecients rather than linear amplitude really isn't that lossy at at all. Considering the reconstruction filter basically plots sinusoidal waveforms between the samples. Plus the signal is band limited to the human hearing range, so there's an upper limit on how accurate the cosine transform has to be.

I still prefer to acquire music in PCM format, but that's just because there are real issues with multi-generational recompressions, and when a better system for compressing audio to take it with me comes along I like to be able to go back to a complete data set for a fresh export.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris

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#401880 - 03/13/14 04:56 PM Re: Sounded like Neal had a great idea until... [Re: ClubNeon]
Murph Offline
axiomite

Registered: 10/05/06
Posts: 6780
Loc: PEI, Canada
Originally Posted By: ClubNeon
Sometimes I wish there was a Kickstopper. A way to pay to keep things from happening.


Like this one that belongs to a brother of a fellow at work here?

How lazy do you have to be before you need a cell phone charger built into your pillow??????
The Power Pillow
_________________________
With great power comes Awesome irresponsibility.

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#402428 - 04/04/14 07:54 PM Re: Sounded like Neal had a great idea until... [Re: Murph]
Serenity_Now Offline
veteran

Registered: 03/28/14
Posts: 149
Loc: PEI, Canada
Hey Guys (especially ClubNeon)

If you have an hour to kill sometime:

What is your take on Allen Sides' interview over at home theater geeks. He addresses pretty much everything talked about here from a recording engineers standpoint.

Interesting (and no doubt controversial) thoughts from a guy in the Biz.

http://twit.tv/show/home-theater-geeks/199
_________________________
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#402434 - 04/05/14 05:42 AM Re: Sounded like Neal had a great idea until... [Re: Murph]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
I stopped watching at the point where he goes into speaker design. I don't have enough background in that to comment with any sort of authority. But I did pay attention to the first half of the video and made some notes.

He mentioned recording at 96 or 192 kHz to avoid the brick-wall filter. I do completely agree with this. Real time, brick-wall filtering is difficult to get correct, and when it is done wrong, it causes audible artifacts. Low-pass filtering can be done better with a dedicated down-sampling process. So yeah, recording at higher sampling rates in the studio makes sense.

But then he goes on to say that the higher sampling rates give more detail at even the audible frequencies. He gives the example of having more samples at 15 kHz. Here he's wrong. I used to make the same mistake, until I actually started doing the math, and understanding how PCM really works. It's simple, the only thing that higher sampling rates give you is the ability to reproduce higher frequencies. Period.

The host brings up inter-modulation distortion from high sampling rates. This is a real problem, but the Allen says he's never noticed it when asked. I'm guessing he has really high quality gear in every location he has the ability to playback 96 or 192 kHz audio. It's less of a issue with well designed gear, because it's purposely worked around, usually by filtering ultrasonics out. Cheaper gear doesn't attempt to do anything, and you can get strange, harsh harmonics in the audible range. If you don't expect everyone to spend 1000s of dollars on studio grade gear for playback, don't give them 192 kHz audio. Do a good down-sampled output, and give them something that doesn't have ultrasonic content.

The story about having different pressings of discs sound different seems familiar. I wonder if I heard it from him before. Back in the 80s there were issues with some pressing houses doing bad jobs at reproducing the master to disc. With today's duplication equipment it doesn't happen anymore. His comment about copies of CDs he's made himself sounding different is likely his personal bias making him hear something that's not there. I'd like to see him prove this with a blinded study. The host is also showed obvious incredulity.

In addition to that Allen didn't answer the question. The person writing in asked why a demo pop song distributed with Logic didn't sound like the mastered CD. He wanted to know what mastering magic is performed. It seems like Allen is a mixing engineer, not a mastering engineer, so it wouldn't be a topic he'd have much to say about. Plus it is a bit larger than can be covered in an one hour podcast.

Toward the end of the first half Allen talks about dynamic range. He mentions recording two tracks one 10 dB hotter. He says the louder track will clip during the louder parts, so he'll use the quieter one there, but uses the hotter to use the higher bits. Again he's wrong. This is a belief left over from analog days, when the noise floor of the media was a real thing. So you'd want your signal to be as loud as possible to give you the largest signal to noise ratio. SNR is fixed with digital, there's no benefit of "using the upper bits." The only place that the a hotter signal matters is in the analog chain, but studio gear has such a low noise floor that it isn't worth mentioning.

So of the five big topics of the talk he was right once. For the most part he doesn't know how digital audio works, and is hearing what he's expecting to hear based on his misunderstanding. He probably has a great ear for mixing, and obvious lots of connections from the number of names he drops, and his good business sense got him where he is. None of those things needs an understanding of how the bits are working behind the scenes.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris

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#402442 - 04/05/14 07:06 PM Re: Sounded like Neal had a great idea until... [Re: Murph]
Serenity_Now Offline
veteran

Registered: 03/28/14
Posts: 149
Loc: PEI, Canada
I'm farther towards the formats can matter camp than some. But in parts of this I was even raising my eyebrows.

I think you hit he nail on the head when you said he is not strong with current digital tech. He is definitely an analog mixing specialist. No doubt, with a keen ear for detail.

I just don't understand how copies that are "bit perfect" can possibly sound different... regardless if copied, streamed, burned, etc. Not with current tech anyway. There are so many processes going on in the "black box" world we live in nowadays, who knows.

I like to periodically check into the HTGeeks shows to see what's new. Most are snoozers, or very basic, but this one was so on topic I had to share it. smile
_________________________
Kitty on my foot and I wanna touch it.

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#402449 - 04/05/14 09:47 PM Re: Sounded like Neal had a great idea until... [Re: Serenity_Now]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10379
I'll discuss a key flaw in his interview, which Chris has also pointed out. When he claimed that higher sampling rates allowed for more samples(especially at high frequencies)and therefore better "resolution", I almost stopped listening because this indicated a complete misunderstanding of the digital sampling process, regardless of his experience in the industry. It was proved mathematically by Nyquist and others over eighty years ago that as long as there were at least two samples at a given frequency that the analog waveform could be reproduced precisely, not just approximated. This has of course also proved to be true in practice, including military and industrial processing where accuracy is a bit more crucial than in audio reproduction.

Some who lack an understanding of the basis of the sampling process view the samples as if they were involved in a sort of "connect-the-dots" procedure where the more dots you had, the closer you got to the original analog waveform, but you never could get there with full analog completeness. Again, nothing of the sort is going on; only two samples are necessary to establish unambiguously the precisely frequency involved at that instant. The perhaps 2000 samples available around 20Hz(at a 44.1Kb/s sampling rate)in no way add more accuracy than the as little as 2 samples taken around 20KHz, and the 20KHz wave is reproduced just as precisely(rather than being simply a straight line connecting 2 dots).

With his misunderstanding coloring his subjective views, this doesn't allow me to take seriously any of his claims about "amazing", "unbelievable"(at least as he intended the term), etc. results he experienced.
_________________________
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Enjoy the music, not the equipment.



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#402455 - 04/05/14 11:06 PM Re: Sounded like Neal had a great idea until... [Re: JohnK]
ClubNeon Offline
connoisseur

Registered: 02/06/09
Posts: 3448
Loc: Western Maryland, USA
Originally Posted By: JohnK
The perhaps 2000 samples available around 20Hz(at a 44.1[kHz] sampling rate)in no way add more accuracy than the as little as 2 samples taken around 20KHz...

In fact if you have a band-limited signal, those extra samples are completely wasted. Part of MP3 encoding process is to split the full audio spectrum into multiple bands, and only allocate as many coefficient values as are needed to reconstruct the upper frequency of each band.
_________________________
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs
-Chris

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