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Author Topic: Spectrum analyzer: scale is linear and reversed  (Read 2773 times)

negopus

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Spectrum analyzer: scale is linear and reversed
« on: April 18, 2006, 02:57:40 pm »

I installed Media Center 11.1 only recently.

With some pleasure, I noticed two spectrum analyzers on the display bar. I understand that this feature is only for entertainment, and not a studio tool. But it has a couple of limitations: the frequency scale is linear, and the left scope has the frequency axis reversed. Maybe only few people noticed that the scale is linear. You can devise it by playing a linear sweep from Fred Nachbaur's test signals http://www.dogstar.dantimax.dk/testwavs/. The linear scale may be more visually entertaining, and is also easier to code, as it is a straight visualization of the FFT amplitude, but the user should have the choice to use a log scale, that is more musically meaningful, as each octave occupies the same horizontal space.

Two frequency analyzers are too many. The second is almost useless. With a standard vision, you cannot focus and concentrate on both scopes. They are too far, and one is reversed, so you cannot tell the differences between left and right channel (what happens with multi channel audio, by the way?). I think that adding a waveform visualization is a better idea. It is visually entertaining too, and you can quickly switch your attention from one to another, from time domain to frequency domain and vice versa.

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Matt

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Re: Spectrum analyzer: scale is linear and reversed
« Reply #1 on: April 18, 2006, 03:00:33 pm »

The scale used is logarithmic, not linear.  Exact parameters have been tuned for looks.  Each analyzer represents one channel.

JGreen has had good luck with an eye patch.
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Matt Ashland, JRiver Media Center

negopus

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Re: Spectrum analyzer: scale is linear and reversed
« Reply #2 on: April 18, 2006, 03:56:23 pm »

I am not sure about the frequency scale being logarithmic. I have the output of my card fed back to InspectorXL http://www.elementalaudio.com/products/inspectorxl/index.html for reference (cannot use the DirectX host plug-in as its video refresh rate is too low). The behaviour of a spectrum analyzer with a log scale is pretty different. When playing a linear sweep (20 Hz to 20 kHz), a log analyzer shows the peak moving initially very fast, then slowing down when the frequency increases. In the MC analyzer the peak of the linear sweep moves at a constant speed.
Also, the linear sweep reaches the upper bound of the analyzer's frequency scale at about 14 kHz. Frequencies above that are not displayed. Again, this might be a design choice, because the linear-scale spectrum is more fun to watch below 14 kHz, and compressed audio is usually filtered above 16 kHz.



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jgreen

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Re: Spectrum analyzer: scale is linear and reversed
« Reply #3 on: April 18, 2006, 03:57:18 pm »

Actually not an eye patch, but an adhesive bandage, which I use to hold my left eyelid shut.

Neg, to you and me, the current SA setup may seem like something out of the Ministry of Silly Walks, or the Argument Department (or is it the contradiction department--no it isn't).  But I can tell you that jriver loves their backwards/left-handed SA, and they're stickin with it.  I myself have grown kind of fond of it, over time, and I often find myself playing little mind games to see if I can actually mentally process two separate Spectrum channels (one of which is reversed) simultaneously.  Short of hyperventilating, I can't think of a quicker way to get so dizzy you fall over backwards.

As for analyzing audio, what's the goal here?  I was reviewing your post on SA programs, loopbacks, etc, and I've been trying a few things myself.  For sheer entertainment, ghammer's Izotope/Ozone 3 gives great visuals and great precision, all for a $250 price tag that makes me think they've been sniffing auto exhaust.  Plus, since I load in a 4-second buffer, everything it reports is 4-seconds ahead of the sound (AHEAD).  If only that was the NYSE ticker, we'd really have something there. . .

Meanwhile, the much-maligned backward/left-handed audio parsley dingus is virtually dead on, maybe two-tenths of a sec early.  So I agree, I'd love to see jriver develop an elaborate SA visualization, and I would point out that Izotope is getting $250 a pop for theirs, or at least got that much out of Ghammer.
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Doof

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Re: Spectrum analyzer: scale is linear and reversed
« Reply #4 on: April 18, 2006, 03:59:37 pm »

Um... what's the point, exactly? What can one actually accomplish by watching a spectrum analyzer?
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Mr ChriZ

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Re: Spectrum analyzer: scale is linear and reversed
« Reply #5 on: April 18, 2006, 04:10:53 pm »

Enlightenment =)

negopus

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Re: Spectrum analyzer: scale is linear and reversed
« Reply #6 on: April 18, 2006, 04:12:20 pm »

It seems that buffer delay compensation is missing in all audio players using external visualization plug-ins. If I load InspectorXL in Winamp (using VB-Audio DirectX rack and VST-DX adapter) it displays audio in advance, exactly the amount ot the buffer. Plug-ins and adapters should become aware of that problem, and add some delay to compensate. Of course, if they are used for visualization only, not for audio processing too.

I don't know Izotope/Ozone 3, but InspectorXL is dedicated to audio visualization only. There's a free version of it too, named just Inspector http://www.elementalaudio.com/products/inspector/index.html.
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