cspect is a real-time signal analysis program for SGI computers. On launch, the "time display" window is displayed and the program starts reading in data from the microphone input (this can be changed to a line input or an aiff/aiffc soundfile) and displays the RMS level of the input in a rolling display.
cspect-2.2.1996: description + notes
Basic Controls
SPACE BAR- Pressing the space bar pauses/unpauses the input.
AXIS BUTTONS- The buttons to the left of the level axis change the axis range. The upper two buttons expand and contract the scale while the lower two buttons shift the scae up and down.
The buttons to the left of the frequency axis on the spectrogram display change the axis range by incrementing and decrementing the frequency values at the beginning and end of the axis. The two upper buttons increment and decrement the end of the axis and the two upper buttons increment and decrement the beginning of the axis.
The buttons at the bottom right of the time and frequency axes shift the display left or right. If a duration or frequency range has been selected then the step size is equal to the selected duration/frequency range. If spectra are being calculated during shifting, the step size is divided by the FFT Overlap value. If Play has just been performed on the selected duration, the selected duration is played for each shift. Likewise, if Spectrum has been requested, the spectrum is calculated for each successive position of the selected duration.
LEFT MOUSE- When the input is paused, dragging the left mouse button across the display selects a range of the input to zoom in to, play, or compute the spectrum of. The selected area is colored blue and the selected time/frequency is displayed above.
MIDDLE MOUSE- Clicking the middle mouse button within the display produces a cursor with the time/frequency and level corresponding to the cursor position displayed above.
RIGHT MOUSE- The right mouse button produces a pop-up menu. The various components of the menu for the different displays are described below.
Time Display pop-up menu
Zoom In- zoom in to selected duration or decrease time axis range by a factor of 2.
Zoom Out- undo previous zoom in.
Play- plays selected duration over headphones or speaker.
Spectrum- if input is paused, calculates spectrum of selected time using FFT. The size of the FFT depends on the selected duration. A four second selection will take some time but give frequency resolution down to 0.25 Hz! The spectrum is displayed in the "spectral display" window.
Trigger- if selected, then the input will keep running until the input level exceeds the value on the right of the display, after which 3/4 of the display will be filled then the input will be paused.
Input Source- Microphone, Line, or Soundfile. If the latter, then a Motif FileSelectionBox is displayed. An input file can also be put on the command line, i.e. "
cspect filename".Input Channel- Left or Right.
Ordinate Units- Volts: linear amplitude (this probably isn't calibrated right - I guessed). If Envelope is selected then two lines are displayed joining max and min amplitude values. A middle mouse click above 0 V puts the cursor on the upper envelope, a middle mouse click below 0 V puts the cursor on the lower envelope. RMS dB: a running RMS level in dB is displayed.
Sample Rate- input sample rate.
DC Correction- Default: uses values defined in main.c to remove DC - may need to be modified according to input source etc. Auto: removes DC on the fly using IIR filter. May slow things up a bit and can filter out very low frequencies. Keep: uses last calculated DC correction value. Off: no DC correction.
Hint: use Auto to get DC correction then Keep for speed and to avoid removing low frequency components.
Display- can have all or any of Time Waveform, Spectrum, Spectrogram, or Waterfall.
Save As ASCII- save x,y coordinates of plot to text file (time normalised to start at zero). In Envelope mode, max and min curves are listed consecutively.
Spectrum Display pop-up menu
Zoom In- zoom in to selected range or decrease frequency axis range by a factor of 2.
Zoom Out- undo previous zoom in.
Average- if selected, perform running spectral average of incoming waveform. Stopped by pausing input with the space bar.
Excitation- if selected, display cochlear excitation pattern (shows vibration of basilar membrane as a function of centre frequency).
Pre-emphasis- 6-dB/Octave spectral pre-emphasis.
Ordinate Units- Spectral Envelope or Spectrum Level (= power per Hz).
FFT Size- number of points in FFT for real-time spectrum.
FFT Overlap- FFTs are spaced (FFT Size)/(FFT Overlap) samples apart.
Window Type- windowing performed on input prior to FFT. Can have: Rectangular (no windowing), Hamming, Hanning, Bartlett, Blackman, or Blackman-Harris.
Display- same as time display popup.
Save As ASCII- save x,y coordinates of plot to text file.
Spectrogram Display pop-up menu
Boost- increase intensity.
Unboost- decrease intensity.
Excitation- same as spectral display popup.
Pre-emphasis- same as spectral display popup.
Color- nauseating colors. In decreasing intensity - white < yellow < red < blue.
Invert Colors- inverted grey scale or even more nauseating colors.
Plot Mode- Scroll: left to right overwriting previous. Roll: right to left moving display.
FFT Size- same as spectral display popup.
FFT Overlap- same as spectral display popup.
Window Type- same as spectral display popup.
Display- same as time display popup.
Waterfall Display pop-ups
Click with the right hand mouse to the left of the display to get the time display popup, click to the right of the display to get the spectrum display popup. These control the time and frequency aspects of the display respectively.
Save As ASCII saves all the data as time,frequency,level.
Notes: The spectrogram and waterfall displays work by moving great chunks of the screen pixel data around. To avoid messy graphic effects they always try to pop themselves to the top of the window stack when plotting data. The only way to disable this is to turn the display off using the Display option in the popup menu.
To auto-install this package, go back and click on the respective install icon.