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Some thoughts on "high resolution" audio processing Dynamics Plugins
Old 8th December 2014
  #151
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i have a drum track and/or a full mix at 88.2 we could use if we wanted something transient-heavy to test out.
Old 8th December 2014
  #152
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Quote:
Originally Posted by bogosort View Post
...Factor in all the potential ultrasonic noise sources and it's not difficult to see how real-world IMD increases with bandwidth. This is not an academic issue.
This is true however very few microphones reproduce anything above around 30k and most professional gear has a built in low pass filter to keep RFI out. The loss due to air absorption also means it would only be audible up close.

How you limit bandwidth is critical to sound within the audible range but a serious argument can be made that failing to limit bandwidth is equally critical to sound quality within the audible range.
Old 8th December 2014
  #153
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Quote:
Originally Posted by bogosort View Post
Most acoustic instruments produce ultrasonic energy, though usually only a tiny percentage of their audio energy. Some percussive instruments have significant ultrasonic energy, for example as much as 40% of total energy in a cymbal strike may be ultrasonic: There's life above 20 kilohertz! A survey of musical instrument spectra to 102.4 kHz
But can we trust this paper when this is written at the top.
Quote:
At the request of people involved in standards-setting for audio, who wanted this information made available as soon as possible, I published this original paper here, rather than in a professional journal.
Old 9th December 2014
  #154
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Quote:
Originally Posted by stinkyfingers View Post
i have a clip/file i could share to use for 'study' purposes. what length do you want ? 30 seconds worth ?
it's just an analog synth patch recorded @ 96kHz and there's is a '****-ton' of HF energy. iirc this track created huge problems trying to get it cut to vinyl, so much i think they just skipped it all-together.
anyway, it's not a 'hi-fi' quality recording or anything (it was done on a focusrite ), but it's a 'real world' scenario of recording significant amounts of HF and what happens as a result...
Quote:
Originally Posted by scraggs View Post
i have a drum track and/or a full mix at 88.2 we could use if we wanted something transient-heavy to test out.


Fire away!
Old 10th December 2014
  #155
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Old 10th December 2014
  #156
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all very relevant for outdoor distance recording. wait a minute, what about wind direction?
Old 10th December 2014
  #157
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Originally Posted by Timesaver800W View Post
all very relevant for outdoor distance recording. wait a minute, what about wind direction?
Really? How close do you put your mic's in an orchestra setting, then?

You mike the cymbals from 1' away?
Old 11th December 2014
  #158
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with that we've moved well and truly beyond the scope of this thread. mic technique? air absorption/damping as propaganda for bandwidth denial? me think not (no offence).
Old 12th December 2014
  #159
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based on the original test in the thread, i took a 96kHz synth track, *src from 96>48>96kHz and then from each track i removed < 5000kHz (via *src), so imd would be visible there. then i applied the js_saturation to each...

green = original 96kHz track + saturation
red = src 96 > 48 > 96kHz +saturation

saturation @ 20%...



saturation @ 100%...



i got 99 problems but 'extra' imd from more bandwidth ain't one...

(*src = SoX, 'rate -v -s')
Old 12th December 2014
  #160
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Quote:
Originally Posted by stinkyfingers View Post
i got 99 problems but 'extra' imd from more bandwidth ain't one...
How'd you come to that conclusion? I see way more IMD in the green spectrum than the red (look between peaks in the 20 to 500 Hz region).
Old 12th December 2014
  #161
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Quote:
Originally Posted by bogosort View Post
How'd you come to that conclusion? I see way more IMD in the green spectrum than the red (look between peaks in the 20 to 500 Hz region).
by listening

obviously more in = more out...but how much does it take to make a noticeable difference ?
with the fundamental frequencies being so high in level and density, can you really hear all that stuff down below ?

edit: and not only does the analog synth have a high noise floor, but this 'patch' is pretty much imd to begin with...so more will just 're-inforce' what is already there, possibly making it sound 'better'...if it can even be heard, that is...

context is everything...
Old 12th December 2014
  #162
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Indeed, the IMD is lower than the avg noisefloor of outboard gear, as mentioned before, not a real world problem.
Old 12th December 2014
  #163
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Obviously the audibility and "objectionableness" of IMD products will depend on the specifics of the situation, but it is clear that higher bandwidth processing can increase distortion levels. Blanket statements that it's not a real-world problem are assuming too much. Especially considering that many seem to be using double-bandwidth rates specifically to reduce distortion (in the form of aliasing), one would think that this is pertinent.
Old 12th December 2014
  #164
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Same here, I see MUCH more IMD in the green file and really cannot follow your conclusions. The easily 12-20dB higher "noise floor" over the full spectrum is more than obvious. Even DC seems to have grown by ~12dB. After ONE light saturation! Now try this again with 2 or 3 saturators and 192kHz.


We're working hard on a little filter tool which can be simply thrown into a playback or processing chain for direct evaluation in real world situations. Our first tests showed a surprisingly strong, almost exciting effect in hot driven chains. It's easy to hear the mud disappearing, with all low/lowmids clearly becoming more audible. Even simple playback suddenly sounds richer, similar to a reduction in noise floor. Pls give me a few more days to make it available.
Old 12th December 2014
  #165
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For sure I'm going to test this one, once available, curious what the audible difference will be. And we won't be throwing the baby out with the bathwater, a very well isolated quiet room measures something like 25dB even the peaks at -75dB at normal listening levels are not a problem
Quote:
Originally Posted by FabienTDR View Post
Same here, I see MUCH more IMD in the green file and really cannot follow your conclusions. The easily 12-20dB higher "noise floor" over the full spectrum is more than obvious. Even DC seems to have grown by ~12dB. After ONE light saturation! Now try this again with 2 or 3 saturators and 192kHz.


We're working hard on a little filter tool which can be simply thrown into a playback or processing chain for direct evaluation in real world situations. Our first tests showed a surprisingly strong, almost exciting effect in hot driven chains. It's easy to hear the mud disappearing, with all low/lowmids clearly becoming more audible. Even simple playback suddenly sounds richer, similar to a reduction in noise floor. Pls give me a few more days to make it available.
Old 12th December 2014
  #166
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Quote:
Originally Posted by FabienTDR View Post
Now try this again with 2 or 3 saturators and 192kHz.
the real problem here is why are 'audiophiles' using so many saturators in series ? don't they know it's a lot more productive to just straight up clip it ?
Old 12th December 2014
  #167
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Not audophiles, for audio engineers! Real, measurable stuff you know. This is not about resonating stones, CD enhancer sprays or similar.

btw, bandwidth/IMD considerations are very real in radio/tv broadcast tech (and certainly not news, they mess with such problems since decades).

Super wide bandwidths raise new questions (both for storage, processing and playback). It's important to be aware of these effects, that's all. I am certain that most people will hear the (negative) effects of IMD if presented in an accessible, easily comparable manner.
Old 12th December 2014
  #168
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Let's wait what your new baby will bring, you have a reputation to live up to with your previous releases, So i expect to hear immediate upside
Old 12th December 2014
  #169
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Quote:
Originally Posted by FabienTDR View Post
We're working hard on a little filter tool which can be simply thrown into a playback or processing chain for direct evaluation in real world situations. Our first tests showed a surprisingly strong, almost exciting effect in hot driven chains. It's easy to hear the mud disappearing, with all low/lowmids clearly becoming more audible. Even simple playback suddenly sounds richer, similar to a reduction in noise floor. Pls give me a few more days to make it available.
Please put it into Slick EQ GE's filter section too. I've been experimenting recently with leaving the 40kHz LPF on in SlickEQ just before the analogue chain, and again, just before the final digital limiter, for just the reasons outlined in this thread, and I think I can hear a difference, although I haven't tried ABXing it yet. Would be great if it was built in as then wouldn't need to have another plugin/more screen real estate etc.
Old 12th December 2014
  #170
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Quote:
Originally Posted by Hermetech Mastering View Post
Please put it into Slick EQ GE's filter section too. I've been experimenting recently with leaving the 40kHz LPF on in SlickEQ just before the analogue chain, and again, just before the final digital limiter, for just the reasons outlined in this thread, and I think I can hear a difference, although I haven't tried ABXing it yet. Would be great if it was built in as then wouldn't need to have another plugin/more screen real estate etc.
I think this LPF should be hardcoded (the user must not adjust its parameters). Check attached image for UAD Massive Passive MST (default settings) built-in LPF. 88.2k sample rate was used.

The problem with SlickEQ is because this LPF contradicts with "delta" signal processing used. So we must add another processing option, something like "limited bandwidth mode". But we can add it when we find the best sounding LPF.
Attached Thumbnails
Some thoughts on &quot;high resolution&quot; audio processing-massivepassive.jpg  
Old 13th December 2014
  #171
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What name will they think of next?

Un-Doppelganger?
Old 16th December 2014
  #172
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Ok, we (Vlad and myself) finally found the time to set up a first version of an ultrasonic filter meant to address the problem. This is an alpha version, this means that detailed documentation is still missing and basically everything is potentially subject to change. Also, we haven't tested this plug-in in the wild yet, expect some hick-ups here and there...



Win (installer)
http://www.tokyodawn.net/labs/Ultras...installer).zip

Win (no installer)
http://www.tokyodawn.net/labs/Ultras...installer).zip

Mac bundle
http://www.tokyodawn.net/labs/Ultras...c%20Filter.dmg


Behind the interface lies a very precise linear phase filter specifically tuned for the task of IMD optimisation in super-wideband processing chains (and playback!).

It offers 3 simple parameters and a bypass button:

- The corner frequency (specified as the point where the filter achieves 0.1dB of attenuation).
- The filter slope steepness.
- Amount (similar to a simple dry/mix function, but dB based).


To be honest, I was shocked to hear the difference it made when playing back 96kHz masters. My monitoring chain certainly isn't the worst, but the effect of the filter is easily ABX'able for most "hotter" tracks. I start to feel like an audiophile salesman, so I'll stop here (lol, the tool is free, no worries ). But let me know your thoughts!



Specifically, I'd love to hear your feedback for the following use-cases:

- Using the filter in front of the final limiter during mastering.
- Using the filter to improve playback quality of wideband systems/configurations.
- Using the filter to remove/reduce excessive "out of band" content (for restoration).
Old 16th December 2014
  #173
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Quote:
Originally Posted by FabienTDR View Post
Ok, we (Vlad and myself) finally found the time to set up a first version of an ultrasonic filter meant to address the problem.
Thank you - looking forward to trying it out.

Based on much of what has been discussed above it seems the best places to use it is:

A) to immediately process a high SR capture on recording (i.e. limit the signal bandwidth before you do anything else to it).

b) following nonlinear processes (saturation, compression, etc.)

Yes/no?
Old 16th December 2014
  #174
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Well, both are certainly worth a try, and now, just a click away!
Old 16th December 2014
  #175
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I think before the non-linear processes would be the better bet, but yeah, it's free to try and A/B it for ourselves. Congrats and thanks Fabien!
Old 16th December 2014
  #176
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Will check it out for sure, is audible high-low shelving part of the intended result?
In other words using EQ low high pass filters obviously alter sound, is above supposed to be transparent other than chopping off the bad stuff?
Old 16th December 2014
  #177
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Just tested VST 32 on Win 7 64 in RX4 Advanced and Audiomulch, with both 44.1 and 96kHz files, offline and realtime. Whatever I do it just tells me: "System bandwidth close to audible bandwidth. Filter bypassed". Is that normal? When I apply/render in RX4 it DOES work though (can see its effect on the spectrogram).
Old 16th December 2014
  #178
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@analogue Mastering: It's purely meant to remove the "bad stuff" that could trouble fidelity of processing and playback. The filter is specified at the -0.1dB point (rather than the -3dB typically used to specify filters) and the frequency cut-off range is restricted to 20kHz-25kHz. Passband ripple is almost unmeasurable. All this is meant to reliably prevent the filter from affecting the audible band. In other words, it's maximally transparent ("as much as possible"). The idea is to give the engineer an easy way to A/B the benefits and drawbacks of the filter.

@Hermetech Mastering: This is interesting, we'll have a closer look at the issue. We switch the filter off for Bandwidths smaller than 24kHz, and enable it as soon the host reports an adequate samplerate. It seems that there's a problem somewhere, we'll try to reproduce and fix the issue.
Old 16th December 2014
  #179
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Cheers Fabien, it is strange! Using an RME HDSPe AES clocked externally by a Crookwood converter, if that helps at all.

Very similar to the filters used in sample rate conversion, right? Best of those I've heard (more like not heard, haha) is the one in FinalCD, although not sure if that would be possible in a real time plugin.

http://www.sonicillusions.co.uk/finalcd.htm
Old 16th December 2014
  #180
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It's probably just a DAW/plugin communication problem, a small bug in our code.

Yes, it's similar to SRC filters, but much less aggressive. That is, the ultrasonic filter can use smoother filtering than most SRC's situations ask for.

Quality wise, there's nothing to worry about. Behind all this is a brute force FIR filter, an exceptionally precise filter structure.
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