Trumco is a Java command which can generate high quality spectrograms.
It was developed as a personal programming exercise, and to research waveform analysis with very little knowledge of how spectrograms are traditionally computed or understood. As a result of its experimental nature Trumco provides uncommon configuration options, and can achieve visually striking levels of plot detail.
In addition to the normal spectra displayed in green and blue channels, Trumco renders 'solvency' in red, which was first implemented as a test channel and is included as a curiosity and visual depth enhancement over the standard spectrogram. Technically, red values are high when the sinusoid which is indicated by the greenblue, value reduces the waveform complexity by the same measure of its own complexity when subtracted from the waveform:
red= greenblue //
*( integral(abs(derivative(waveform)))
-integral(abs(derivative(waveform-sinusoid))) )
/( integral(abs(derivative(sinusoid))) );
Trumco is different in permitting transform windows of arbitrary length from 1 to about 100,000 samples, and output image sizes from 1 by 1 to over 10,000 by 10,000 pixels. However, it does employ a lot of working memory, especially to produce big images with big transform windows.
The 2 main factors of working memory demand are image height and transform window size. A 1000 pixel high plot, with 10,000 sample window requires approx 10 * 1000 * 10,000 bytes = ~100 Megabytes of system RAM to run. Output plot length has relatively little effect on required RAM but is a factor of plot generation time.
Trumcos performance is not shabby, but very large plots with long windows may take some time to complete, perhaps minutes. On such occasions, to relieve the suspense, an estimate of plot generation time is reported.
Trumco runs from a command window or script.
java trumco.class sourcetrack.wav
- makes a plot of the whole file.
java trumco.class sourcetrack.wav -aplts 10 -ovlap 100 -pltln 1000
- makes 10 overlapped plots of the whole file.
-pltht n
- set plot height in pixels
-pltln n
- set plot length in pixels
-ovlap n
- set plot overlap in pixels, for multiple output plots.
- (to improve readability of plot sequences).
-noaxt
- dont draw time axis
-noaxf
- dont draw frequency axis
-fiwvl
- label frequency in wavelengths instead of Hertz
-logfs
- plot frequency axis as logarithmic progression instead of linear.
- ( tends to overplot lower frequencies and sparsely plot highs )
-gamma n
- applies gamma adjustment to plot rendering
- (can improve appearance but distorts measurements)
- If set to 1, green and blue pixel values of 255 will indicate a potential sinusoidal component with amplitude equal or exceeding -mxamp. Pixel values under 255 will indicate an amplitude of mxamp*value/255
-aplts n
- 'autoplots' sets measure leap (time resolution) automatically to produce the specified number of plots for given audio file or a specified time range within file.
-tprpl n
- 'time per plot', auto sets measureleap to fit time per plot (in millisecs)
-lpsmp n
- 'leap samples' Number of samples progressed for every measure.
- (This sets the time-scale of the horizontal axis)
-lptim n
- same as -lpsmp, expressed in millisecs. (millisecs per pixel)
-rleap n
- round 'measure leap' down to whole sample length, (fwiw).
-dursp n
- duration to plot in millisecs
-stspc n
- start plot at n millisecs
-fnspc n
- finish plot at n millisecs
-mxamp n
- maximum amplitude to expect in audio,
- affects brightness of spectrogram.
-pxamp n
- precalculate maximum amplitude and adjust by factor n.
- plot range is pre-passed to estimate maximum amplitude before plotting, and optionally adjusted by factor n.
- e.g. "-pxamp 0.5" sets mxamp to 0.5 * maximum amplitude estimated by pre-pass.
-minwv n
- maximum hertz to render, expressed in wavelength as samples
-maxhz n
- same as minwv, expressed in hertz
-maxwv n
- minimum hertz to render, expressed in wavelength as samples
-minhz n
- same as maxwv, expressed in hertz
-mrsmp n
- set size of measurement window in samples.
- analogous to a transform window length (number of samples 'heard' in one pixel)
-mrtim n
- same as mrsmp only expressed in milliseconds.
-chnnl n
- for stereo tracks, sets channel to render ( 0 or 1 )
-chnnl 2
- for stereo tracks, downmixes channels.
-chnnl 3
- for stereo tracks, renders the difference between channels
-rawfl [samplerate] [channels] [bytes per sample] [endian]
-
to read as raw pcm, this switch and details must follow the filename in order:- any samplerate stated in hertz, 1|2 channels, 1|2 bytes per channel, big endian word order is default, add 'e' for little endian.
-
e.g. java -jar trumco.jar filename.aif -rawfl 44100 2 2 e -stspc 2
-namex ext
-
adds an extension ext to output file names, to avoid overwrites.
-
e.g. srcfileext.00.bmp, srcfileext.01.bmp, etc..
....