Spectrograms - Revision history

Martinwguy: /* Inverse spectrograms */

2025-09-21T08:50:05Z

Inverse spectrograms

← Older revision		Revision as of 08:50, 21 September 2025
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	=[[Inverse spectrograms]]=		=[[Inverse spectrograms]]=
	There are a few reconversions of spectrograms of unpublished music back into rough audio, created by some [https://~~gitlab~~.~~com~~/martinwguy~~/delia-derbyshire/tree/master~~/anal even hairier custom software]:		There are a few reconversions of spectrograms of unpublished music back into rough audio, created by some [https://codeberg.org/martinwguy/anal even hairier custom software]:
	* ''[[Pot Au Feu early version]]'', to get an idea of the audio quality of the reconstructions		* ''[[Pot Au Feu early version]]'', to get an idea of the audio quality of the reconstructions
	* ''[[Singing Waters]]'', a rain-falling effect whose spectrogram resembles the layout of the poem it tells		* ''[[Singing Waters]]'', a rain-falling effect whose spectrogram resembles the layout of the poem it tells

Martinwguy: /* Logarithmic frequency axis */

2023-02-12T14:16:13Z

Logarithmic frequency axis

← Older revision		Revision as of 14:16, 12 February 2023
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	=Logarithmic frequency axis=		=Logarithmic frequency axis=
	[[Image:Sndfile-spectrogram analysis of The Pattern Emerges.png\|thumb\|right\|The Pattern Emerges - Linear spectrogram from 0 to 22kHz of the whole piece (177 sec)]]		[[Image:Sndfile-spectrogram analysis of The Pattern Emerges.png\|thumb\|right\|The Pattern Emerges - Linear spectrogram from 0 to 22kHz of the whole piece (177 sec)]]
	Most FFT-based spectrographic programs' output ~~has~~ a linear frequency axis, usually from 0Hz to 22050Hz for a CD-quality piece, in which the top half of the graph represents the top octave of the sound, the inaudible 11025-22050Hz band, with all the musical detail crushed into the bottom rows of pixels.		Most FFT-based spectrographic programs' output have a linear frequency axis, usually from 0Hz to 22050Hz for a CD-quality piece, in which the top half of the graph represents the top octave of the sound, the mostly inaudible 11025-22050Hz band, with all the musical detail crushed into the bottom rows of pixels.

	[[Image:Sndfile-spectrogram analysis of The Pattern Emerges 8192x4096 cropped.png\|thumb\|right\|The Pattern Emerges - linear spectrogram from 0 to 4kHz of the first 20s (the bottom left corner of the above)]]		[[Image:Sndfile-spectrogram analysis of The Pattern Emerges 8192x4096 cropped.png\|thumb\|right\|The Pattern Emerges - linear spectrogram from 0 to 4kHz of the first 20s (the bottom left corner of the above)]]

Martinwguy: update links to code

2021-07-13T15:03:19Z

update links to code

Martinwguy: /* Inverse spectrograms */

2021-07-13T14:36:07Z

Inverse spectrograms

← Older revision		Revision as of 14:36, 13 July 2021
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	=[[Inverse spectrograms]]=		=[[Inverse spectrograms]]=
	There are a few reconversions of spectrograms of unpublished music back into rough audio, created by some [https://~~github~~.com/martinwguy/delia-derbyshire/tree/master/anal even hairier custom software]:		There are a few reconversions of spectrograms of unpublished music back into rough audio, created by some [https://gitlab.com/martinwguy/delia-derbyshire/tree/master/anal even hairier custom software]:
	* ''[[Pot Au Feu early version]]'', to get an idea of the audio quality of the reconstructions		* ''[[Pot Au Feu early version]]'', to get an idea of the audio quality of the reconstructions
	* ''[[Singing Waters]]'', a rain-falling effect whose spectrogram resembles the layout of the poem it tells		* ''[[Singing Waters]]'', a rain-falling effect whose spectrogram resembles the layout of the poem it tells

Martinwguy: /* Get spectrograms of your music! */

2021-07-13T14:35:00Z

Get spectrograms of your music!

← Older revision		Revision as of 14:35, 13 July 2021
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	If this interests you, please [[Donate\|Make a small donation]] and email <TT>delia.derbyshire.net@gmail.com</TT> attaching the sound file you would like turned into a picture.		If this interests you, please [[Donate\|Make a small donation]] and email <TT>delia.derbyshire.net@gmail.com</TT> attaching the sound file you would like turned into a picture.

	Alternatively, if you can compile C for Linux, you can fetch [https://~~github~~.com/martinwguy/spettro spettro from ~~github~~], which plays music files while showing a log spectrogram of it scrolling right to left with the current playing time at centre screen.		Alternatively, if you can compile C for Linux, you can fetch [https://gitlab.com/martinwguy/spettro spettro from gitlab], which plays music files while showing a log spectrogram of it scrolling right to left with the current playing time at centre screen.

	=[[Inverse spectrograms]]=		=[[Inverse spectrograms]]=

Martinwguy: /* Get spectrograms of your music! */

2021-07-13T14:34:16Z

Get spectrograms of your music!

← Older revision		Revision as of 14:34, 13 July 2021
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	* number of pixel columns per second on the time axis (usually 50)		* number of pixel columns per second on the time axis (usually 50)

	Optionally the software can superimpose single-pixel black and white lines at the frequencies of the piano keys and three-pixel-wide white lines at the positions of the manuscript ~~stave~~ lines, see the example on the right.		Optionally the software can superimpose single-pixel black and white lines at the frequencies of the piano keys and three-pixel-wide white lines at the positions of the manuscript staff lines, see the example on the right.

	If this interests you, please [[Donate\|Make a small donation]] and email <TT>delia.derbyshire.net@gmail.com</TT> attaching the sound file you would like turned into a picture.		If this interests you, please [[Donate\|Make a small donation]] and email <TT>delia.derbyshire.net@gmail.com</TT> attaching the sound file you would like turned into a picture.

Martinwguy: /* Software */

2020-05-08T05:40:31Z

Software

← Older revision		Revision as of 05:40, 8 May 2020
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	{{Thumb\|Noah - Grayscale spectrogram by mkjpg}}		{{Thumb\|Noah - Grayscale spectrogram by mkjpg}}

	The WikiDelia's spectrum analyser, [https://github.com/martinwguy/delia-derbyshire/tree/master/anal "mkjpg"], was written specifically for it using a modified version of [http://www.mega-nerd.com/libsndfile/tools/#spectrogram sndfile-spectrogram] to prepare a linear spectrogram which is then distorted by ~~[https://github.com/martinwguy/delia-derbyshire/tree/master/anal~~ an ImageMagick script] to give it a logarithmic frequency axis.		The WikiDelia's spectrum analyser, [https://github.com/martinwguy/delia-derbyshire/tree/master/anal "mkjpg"], was written specifically for it using a modified version of [http://www.mega-nerd.com/libsndfile/tools/#spectrogram sndfile-spectrogram] to prepare a linear spectrogram which is then distorted by an ImageMagick script to give it a logarithmic frequency axis.

	The program "Sox" can also be used to produce the linear spectrogram, but you need [http://github.com/martinwguy/sox this modified version] to remove the limits on output image size, to normalise the output's brightness, and to make it 250 times faster and not need 16GB of RAM.		The program "Sox" can also be used to produce the linear spectrogram, but you need [http://github.com/martinwguy/sox this modified version] to remove the limits on output image size, to normalise the output's brightness, and to make it 250 times faster and not need 16GB of RAM.

Martinwguy: /* Usage in the WikiDelia */

2019-02-10T13:00:32Z

Usage in the WikiDelia

← Older revision		Revision as of 13:00, 10 February 2019
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	=Usage in the WikiDelia=		=Usage in the WikiDelia=
	The spectrogram of a piece goes in ~~three~~ places:		The spectrogram of a piece goes in two places:
	* On the piece's page in a section '''Spectrogram''' usually just above '''Availability''' so that the Listen button is near.		* On the piece's page in a section '''Spectrogram''' usually just above '''Availability''' so that the Listen button is near.
	* Spectrograms of complete pieces are on the [[Audio]] page		* Spectrograms of complete pieces are on the [[Audio]] page
	* in delia-derbyshire.net/spectrograms
	For example the piece [[Air]] has [[:File:Air.ogg]] and [[:File:Air - Spectrogram.jpg]], used by the MediaWiki macros <TT><nowiki>{{Spectrogram\|Air - Spectrogram}}</nowiki></TT> and <TT><nowiki>{{Spectrogallery\|Air}}</nowiki></TT>		For example the piece [[Air]] has [[:File:Air.ogg]] and [[:File:Air - Spectrogram.jpg]], used by the MediaWiki macros <TT><nowiki>{{Spectrogram\|Air - Spectrogram}}</nowiki></TT> and <TT><nowiki>{{Spectrogallery\|Air}}</nowiki></TT>

Martinwguy: /* Logarithmic frequency axis */

2019-02-10T12:59:11Z

Logarithmic frequency axis

← Older revision		Revision as of 12:59, 10 February 2019
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	What we would like is for each octave to be given the same height in the graph.		What we would like is for each octave to be given the same height in the graph.

	The spectrograms used in the WikiDelia are not the usual kind. Their vertical scale is logarithmic, which gives the same number of pixel rows per ~~semitone~~.		The spectrograms used in the WikiDelia are not the usual kind. Their vertical scale is logarithmic, which gives the same number of pixel rows per octave.

	Not only does this give a graphic representation to music similar to conventional score notation for the notes and rhythms		Not only does this give a graphic representation to music similar to conventional score notation for the notes and rhythms

Martinwguy: /* Get spectrograms of your music! */

2019-01-12T19:53:40Z

Get spectrograms of your music!

← Older revision		Revision as of 19:53, 12 January 2019
Line 66:		Line 66:
	If this interests you, please [[Donate\|Make a small donation]] and email <TT>delia.derbyshire.net@gmail.com</TT> attaching the sound file you would like turned into a picture.		If this interests you, please [[Donate\|Make a small donation]] and email <TT>delia.derbyshire.net@gmail.com</TT> attaching the sound file you would like turned into a picture.

	Alternatively, if you can compile C for Linux, you can ~~get the~~ [https://github.com/martinwguy/spettro spettro on github] which plays music files ~~and show~~ a log spectrogram of it scrolling right to left.		Alternatively, if you can compile C for Linux, you can fetch [https://github.com/martinwguy/spettro spettro from github], which plays music files while showing a log spectrogram of it scrolling right to left with the current playing time at centre screen.

	=[[Inverse spectrograms]]=		=[[Inverse spectrograms]]=

← Older revision		Revision as of 15:03, 13 July 2021
Line 34:		Line 34:
	{{Thumb\|Noah - Grayscale spectrogram by mkjpg}}		{{Thumb\|Noah - Grayscale spectrogram by mkjpg}}

	The WikiDelia's spectrum analyser, [https://~~github~~.com/martinwguy/delia-derbyshire/tree/master/anal "mkjpg"], was written specifically for it using a modified version of [http://www.mega-nerd.com/libsndfile/tools/#spectrogram sndfile-spectrogram] to prepare a linear spectrogram which is then distorted by an ImageMagick script to give it a logarithmic frequency axis.		The WikiDelia's spectrum analyser, [https://gitlab.com/martinwguy/delia-derbyshire/tree/master/anal "mkjpg"], was written specifically for it using a modified version of [http://www.mega-nerd.com/libsndfile/tools/#spectrogram sndfile-spectrogram] to prepare a linear spectrogram which is then distorted by an ImageMagick script to give it a logarithmic frequency axis.

	The program "Sox" can also be used to produce the linear spectrogram, but you need [~~http~~://~~github~~.~~com~~/martinwguy/sox this modified version] to remove the limits on output image size, to normalise the output's brightness, and to make it 250 times faster and not need 16GB of RAM.		The program "Sox" can also be used to produce the linear spectrogram, but you need [https://sourceforge.net/u/martinwguy/sox this modified version] to remove the limits on output image size, to normalise the output's brightness, and to make it 250 times faster and not need 16GB of RAM.

	{{Thumb\|Noah - Grayscale spectrogram by logft}}		{{Thumb\|Noah - Grayscale spectrogram by logft}}
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	An alternative technique would be to perform a Constant-Q tranform directly instead of distorting a linear spectrogram. Candidates are:		An alternative technique would be to perform a Constant-Q tranform directly instead of distorting a linear spectrogram. Candidates are:
	* Judith Brown's brute force algorithm, [http://~~github~~.com/martinwguy/logft "logft"] from 1988-91.		* Judith Brown's brute force algorithm, [http://gitlab.com/martinwguy/logft "logft"] from 1988-91.
	* Brown and Puckett's efficient algorithm,<ref>[http://academics.wellesley.edu/Physics/brown/pubs/effalgV92P2698-P2701.pdf An efficient algorithm for the calculation of a constant Q transform] by Brown and Puckette.</ref><ref>[http://wwwmath.uni-muenster.de/logik/Personen/blankertz/constQ/constQ.html ''The Constant Q Transform''], an implementation in Matlab by Benjamin Blankertz</ref><ref>[http://sourceforge.net/p/sc3-plugins/code/ci/master/tree/source/PitchDetection/Qitch.cpp An earlier implementation in more C-like C++] in a pitch detection plugin for Supercollider, licensed under GPL.</ref> using a precomputed FFT temporal kernel (a what?)		* Brown and Puckett's efficient algorithm,<ref>[http://academics.wellesley.edu/Physics/brown/pubs/effalgV92P2698-P2701.pdf An efficient algorithm for the calculation of a constant Q transform] by Brown and Puckette.</ref><ref>[http://wwwmath.uni-muenster.de/logik/Personen/blankertz/constQ/constQ.html ''The Constant Q Transform''], an implementation in Matlab by Benjamin Blankertz</ref><ref>[http://sourceforge.net/p/sc3-plugins/code/ci/master/tree/source/PitchDetection/Qitch.cpp An earlier implementation in more C-like C++] in a pitch detection plugin for Supercollider, licensed under GPL.</ref> using a precomputed FFT temporal kernel (a what?)
	* An optimized version of the above, "constant-q-cpp", doing octave decimation of the signal to save compute time.<ref>[http://iem.kug.ac.at/fileadmin/media/iem/projects/2010/smc10_schoerkhuber.pdf Constant-Q Transform Toolbox for Music Processing]: An optimization in MATLAB of Brown and Puckette's efficient Constant-Q algorithm.</ref><ref>[https://code.soundsoftware.ac.uk/projects/constant-q-cpp ''C++ Constant-Q''] at soundsoftware.co.uk, a C++ implementation of the above with permissive license.</ref>		* An optimized version of the above, "constant-q-cpp", doing octave decimation of the signal to save compute time.<ref>[http://iem.kug.ac.at/fileadmin/media/iem/projects/2010/smc10_schoerkhuber.pdf Constant-Q Transform Toolbox for Music Processing]: An optimization in MATLAB of Brown and Puckette's efficient Constant-Q algorithm.</ref><ref>[https://code.soundsoftware.ac.uk/projects/constant-q-cpp ''C++ Constant-Q''] at soundsoftware.co.uk, a C++ implementation of the above with permissive license.</ref>
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	* the free audio editor [http://www.audacityteam.org Audacity], though the output is blockier than ours		* the free audio editor [http://www.audacityteam.org Audacity], though the output is blockier than ours
	* the free audio file viewer "[http://www.sonicvisualiser.org sonic-visualiser]", which also has a Constant-Q spectrogram VAMP plugin		* the free audio file viewer "[http://www.sonicvisualiser.org sonic-visualiser]", which also has a Constant-Q spectrogram VAMP plugin
	* the ~~next~~ release of [http://www.mega-nerd.com/libsndfile/tools/ sndfile-tools] (~~after~~ 1.03) ~~will include~~ a new <TT>--log-freq</TT> option to <TT>sndfile-spectrogram</TT> achieving the same effect as here. ~~In the meantime, if~~ you can compile C, you can [https://github.com/erikd/sndfile-tools get it on github].		* the latest release of [http://www.mega-nerd.com/libsndfile/tools/ sndfile-tools] (1.04 or later) includes a new <TT>--log-freq</TT> option to <TT>sndfile-spectrogram</TT> achieving the same effect as here. If your OS has an older version and you can compile C, you can [https://github.com/erikd/sndfile-tools get it on github].

	=Get spectrograms of your music!=		=Get spectrograms of your music!=