Re: Spectral Editing is Not User Friendly

Actually you can export not the exact spectrogram, but just the
intensities of each frequency (first member of each complex tuple
produced by FFT). Then apply it on import to a sound file of user's
choice. Editing such image would produce well defined and intuitive
effect, just like equalizer pass filter does, but more precise. I.e.
you can take spectral shape of one sound and apply it to another.

On 10/9/17, Steve the Fiddle <[email protected]> wrote:
> On 9 October 2017 at 00:34, Federico Miyara <[email protected]>
> wrote:
>
>>
>> Steve and friends,
>>
>> I like the idea of being able to export the spectrogram, edit in an image
>> editor, and then import back into Audacity. I presume that what you have
>> in
>> mind is similar to the software "Photosounder"
>> (http://photosounder.com/).
>> That would be a totally new feature, with only superficial similarity to
>> the current "spectral edit" feature.
>>
>>
>> I don't think it is theoretically possible to edit the spectrogram in an
>> image processor (even if it were a customized one for Audacity) and get a
>> valid spectrogram of the processed signal from which the processed signal
>> could be recovered.
>>
>
>
> See this video:
> https://www.youtube.com/watch?time_continue=37&v=W8MCAXhEsy4
>
> Editing any of those images in an image processor prior to 'converting'
> them to sound does change the sound that is produced. Editing a spectrogram
> in an image processor may not give intuitively predictable effects, but it
> certainly would give an effect. For 'creative' use, the technical
> limitations may be an asset.
>
> Steve
>
>
>
>>
>> First of all, the spectrogram has no phase information, so colors alone
>> cannot represent the correct sound, even the original one. In other
>> words,
>> the spectrogram drawing is not a reversible operation, even if no
>> transformation or effect is applied.
>>
>> Second, the color map is a single-dimension one, defined by the linear
>> interpolation of five colors which are just points on a bi-dimensional
>> color map. Unless we could ensure the map color of the image processor is
>> restricted to the colors contained in the piecewise linear path
>> representing amplitudes, we would get meaningless spectrograms.
>>
>> Third, there is a limitation in resolution given by the size of the
>> window
>> so spectrograms do not present a continuous spatial transition of colors.
>> Instead there are small but noticeable rectangles whose areas depend on
>> the
>> time-frequency uncertainty principle. If the FFT size is large, they are
>> very short (high frequency resolution) and wide (low time resolution); if
>> FFT size is small, they are very tall and narrow instead.
>>
>> A possibility would be to take advantage of the bi-dimensional nature of
>> the full visible color map and represent the FFT complex numbers
>> (retaining
>> the phase information), which are also bi-dimensional, as colors. I guess
>> several people have already tried some experiments on this (I mean the
>> graphic representation; the concept of complex spectrogram is frequently
>> used in signal processing). I also guess the spectrogram image would be
>> stunning but far from being intuitive. Moreover, it would be very
>> difficult
>> to figure out the result of a given graphic effect, as well as what to do
>> with the image to get the desired signal effect.
>>
>> The only practical approach is to simulate the spectrogram editing for
>> very simple operations, such as zero or one gain (or real gain or
>> attenuation).
>>
>> This is the approach we had presented (with Luciano). Our plugin allowed
>> to draw closed regions of arbitrary shape to be either filtered out or
>> retained . The plugin was based on overlapping time-varying FFT filter.
>> Whatever
>> the case, the retained part has gain 1 and the rejected part has gain 0.
>> The
>> idea could be extended to support drawing with an "attenuating pencil"
>> which would apply a given gain (picked from a gray shade map).
>>
>> You mentioned Photosouder. I skimmed through the user guide and there is
>> no hint as to what is actually doing when importing an image. What I'm
>> pretty sure is that when editing an already loaded or computed
>> spectrogram
>> it does not re-synthesize the sound from the image, but processes the
>> signal and recalculates the spectrogram.
>>
>> In other words, for an arbitrary image (say, a photo), it tries to
>> represent it within the available color map and spectral and time
>> resolution without concern for phase, but they have the advantage that we
>> don't know a priori how the image "sounds"... And for a true spectrogram,
>> it just simulates the image editing.
>>
>> Regards,
>>
>> Federico
>>
>>
>>
>> On 06/10/2017 11:19, Steve the Fiddle wrote:
>>
>> Hi Nikita,
>>
>> Spectral Editing in Audacity is a fairly new, and not yet fully
>> developed,
>> feature. Despite its shortcomings, it was considered to still be useful
>> enough to include in the Audacity release.
>>
>> I like the idea of being able to export the spectrogram, edit in an image
>> editor, and then import back into Audacity. I presume that what you have
>> in
>> mind is similar to the software "Photosounder"
>> (http://photosounder.com/).
>> That would be a totally new feature, with only superficial similarity to
>> the current "spectral edit" feature.
>>
>> The current feature is really a 'simulation' of editing the spectrogram,
>> rather than actually editing it. How it works is that the selected
>> spectral
>> region sets two frequency parameters (high and low). Specially crafted
>> effects (the "Spectral" effects) can then use these parameters to control
>> their behaviour. The effects then process the audio data as would any
>> other
>> audio effect. So the effect is not actually acting on the spectrogram -
>> it
>> acts on the audio, and the spectrogram is updated from the processed
>> audio.
>>
>> Steve
>>
>> On 6 October 2017 at 13:38, Nikita Sadkov <[email protected]> wrote:
>>
>>> Hi! It was an amazing discovery, that Audacity now supports spectral
>>> editing - arguably one of the most fundamental features, especially if
>>> you want to synth custom sfx for your project or edit some badly
>>> recorded material from https://freesound.org
>>>
>>> My complain is that it is very obscure and tedious to use in its
>>> current form. You have to separately enable spectral selection and use
>>> "Spectral edit ..." tools under "Effect" menu. I.e. you can't just
>>> press Del to clear the frequencies or use Draw Tool (F3) to paint your
>>> sfx with mouse.
>>>
>>> So I think it would make Audacity order of magnitude more useful, if
>>> it copies UI from Sony SpectraLayers, together with layers, which
>>> works just like a raster editor, but unfortunately lacks waveform
>>> editing capabilities. Also, it would be nice feature to export
>>> spectrum plot into png files, so people could edit it in GIMP and then
>>> import back into Audacity.
>>>
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>>
>>
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>> X
>> 10.5.1)
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>> > About
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When asking for help on this list, please include the following information, so we can
help you properly:

* What operating system you are using (for example, Windows XP or Mac OS X 10.5.1)

* Exactly what three digit version number of Audacity you are using (Help > About
   Audacity, or Audacity >  About Audacity on a Mac computer)

* If this is a recording problem, what equipment you are recording with, and how is it
   connected to the computer?

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