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[i]Please Help Me![/i]: Waveform vs Envelope:

Discussion in 'Sound Science' started by TheSonicTruth, Sep 26, 2018.
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  1. TheSonicTruth

    Well, since no one here can make make up their minds!

    And again it's the goobers on rec.audio.pro that are so hung up on terminology instead of technique.
     
  2. bigshot
    It really isn't a failure to communicate on my part. I don't know how I could possibly have explained the difference between a waveform and an envelope around a waveform clearer. I don't think you are dumb. You're perfectly capable of understanding what I said, you just didn't want to because it didn't fit your preconceived ideas. That isn't a cognitive problem. It's personality based. You seem to run into that in other forums too. The problem isn't all the engineers in the world. It's you.
     
    Last edited: Sep 9, 2019
  3. TheSonicTruth

    Everyone: Skim through this article. About halfway down, determine if the author is using the right terminology:

    http://seanrose.com/Audio/beatlesdmm/
     
  4. TheSonicTruth
  5. bigshot
    no thanks
     
  6. Sonic Defender Contributor
    All I can say is wow.
     
  7. TheSonicTruth

    You don't have to be a fan of KISS or the Beatles. All I'm asking of you all is to determine if the authors of those reviews are using the correct terminology, given the context of those articles.
     
  8. gregorio
    1. The correct term would be "Graphical representation of digital audio data".
    1a. However, that's not "widely used". The most widely used industry term would be "waveform", even though it isn't a waveform! This is because the early designers of graphical representations of digital audio data decided to use a representation which resembled a waveform, so analogue engineers would find it easier to relate to. You can easily see this, zoom right in and you will see a series of steps, not a waveform (which is a continuous function that doesn't have any steps)!

    2. Again, neither! Although "waveform" would be more common.

    We've been through all this before!

    What I described was the origin of the term in music production, many decades ago. However, it's now quite often used for other purposes, as @bigshot stated. Agreed that it's use is therefore rather ambiguous but in practice it's not too bad, usually it's meaning is obvious within the context of discussion or, we can simply ask for clarification if necessary.

    G
     
  9. TheSonicTruth
    1a & 2: THANK YOU! Although you'd get a vicious argument from geoff, Trevor, et al, on Usenet rec.audio.pro on that one! They insist on the term 'envelope', at least in the DAW screen context, and the waveform images I linked to, above.


    Zooming in on a piece of music in Audacity at least, what I see is not steps - stair or otherwise - but random jagged lines connected by dots(samples?). Zooming in on a pure sine wave, IE: 1kHz, I see an approximation of actual waves, again connected by those dots. No stair - or other -steps.
     
    Last edited: Sep 10, 2019
  10. bigshot
    The envelope is the lines around the waveform. It's processing being applied to the sound.
     
  11. VNandor
    This is because what audacity accurately shows you are the sample points. Audacity takes those sample points and connects them with a straight line. It's a reasonable approximation of the actual waveform that's supposed to come out of the DAC at lower frequencies but eventually it won't look anything like the actual waveform as you go higher in frequencies. So, saying that you look at the waveform if you zoom in with audacity would tecnically not be correct, because what you see are the sample points being connected with straight lines (which isn't the same as the actual waveform if that wasn't already clear).
     
    Last edited: Sep 10, 2019
  12. TheSonicTruth

    So basically, whether to call it a series of sample points, a waveform, or an envelope all depend on the frequencies being represented, and the level of magnification.

    There is no cut & dry answer.
     
  13. gregorio
    1. Ah, OK. I've never used Audacity as a professional tool (and technically one could argue it's not a DAW but an Audio Editor) and haven't seen it for quite a few years. There was a time when all DAWs and Audio Editors showed the staircase at maximum zoom but these days it can vary. Izotope for example, has the option of displaying the digital data either as the traditional staircase or with an applied reconstruction filter, which therefore technically doesn't display the digital data but what the analogue waveform would look like. I think Premiere also does this. The most common DAWs (ProTools, Cubase, Logic) show a staircase. The reason for this is that it requires processing time to calculate a waveform view and more processing time to calculate it with an applied reconstruction filter and this has to be recalculated every time the waveform moves (in time, when the zoom level is altered, etc). This can add up to quite a chunk of processing when there are dozens of tracks being displayed (in a multi-track session), which slows down the system and uses processing resources required for real-time plugins. In fact, old versions of Pro Tools avoided this processing hit by not calculating display views during playback, it calculated them on track creation and then wrote/read these views to disk. With today's powerful workstations this really isn't an issue any more and that's why some Audio Editors now display the data differently (not as a staircase) or provide different options.

    You MUST also consider that the "waveform" view has to be effectively quantized to the screen resolution (IE. Quantized to the pixel or block of pixels). So, when you are fully zoomed out, small variations in amplitude cannot be displayed. For example, all digital audio sample values between say +30,000 and +32,767 (16bit max peak value) could/would be displayed as the same value. In other words, when fully zoomed out (and depending on the material of course), we could see a "waveform view" with the characteristic "flat top" or "sausage shape" where all peak values appear to be limited to the same value but in fact the underlying sample data is NOT "flat topped", many/most/all of the peak values could be different but we wouldn't see that unless we zoom in!

    2. Generally you can call it a "waveform", if you're describing the outline-shape of the waveform you can call it an "envelope" but it's a bit ambiguous.
    2a. Correct!!

    G
     
  14. TheSonicTruth
    Thanks Gregorio. I think we've finally cleared it up.

    But to get along with certain denizens of Rec.Audio.Pro, I will use the term 'envelope' in those threads. Annoying some of them! If you have a Google Acct. you should drop in via Google Groups. :D
     
  15. danadam
    Audacity has an option: Preferences -> Tracks -> Display Samples, which lets you choose if from some zoom level it should keep using connected dots or display what they call stems.

    Connected dots:
    connected.dots.png

    Stem plot:
    stem.plot.png
     
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