MQPLOT

2D and 3D display of SNDAN  .mq format analysis files

associated programs: Running mqplot
Internal commands
 

mqplot is a recent merger of the two original SNDAN programs mqdisp and mqdistr. These are also included in this version of SNDAN, for the sake of completion, but are not included in this documentation set. Unlike the much more comprehensive display program for .an format files, monan, mqplot provides no transformation facilities. It will display individual tracks using either 2D or 3D co-ordinate displays, with the ability to 'project' the net amplitude and frequency profiles to the respective axis plane. A track can thus appear as an object in a 3-dimensional space, casting a virtual shadow in two directions.
 

Running mqplot.

mqplot requires several parameters. Typing the program name by itself prints a usage message. If the remaining required parameters are not entered on the command line, they are requested interactively. This is generally the most convenient way to use the program. In some cases, internal defaults are activated if no value is entered. There are further optional parameters (shown enclosed in square brackets), which can also be set using internal commands.
 
mqplot  file.mq  minf  maxf  dur [plot-type] [3D_flag] [start_time] [minamp] [maxamp]

file.mq

The name of the input .mq format analysis file.
minf
The minimum  frequency to plot (Hz). Should normally be at or below the analysis frequency for the file (use showhdr to find this if necessary). Set it higher if you want to zoom in on a frequency range of special interest.
maxf
The maximum frequency to plot (Hz). The upper limit is the Nyquist rate for the analysed soundfile. Unless the sound is known to have prominent high frequency components, setting an upper limit between 2000 to 6000 Hz will display all significant tracks clearly.

In interactive mode, both minf and maxf are requested together.

dur
        The duration to plot (seconds), relative to start-time (which defaults to 0).
plot-type
Type "2" for a 2D plot (frequency/ time), or "3" for a 3D plot (amplitude/frequency/time)
3D-flag
Type 1 to activate projection dots, 0 to deactivate.
The projection dots are used to cast a virtual shadow from tracks to either the amplitude and/or the frequency axis. They are most effective when the plot itself is fairly sparse. In other cases they can be difficult to distinguish from tracks, and are then best left deactivated.
start-time
Use this to set a non-zero start-time (seconds) for the time axis - for example, to zoom in on the decay segment of a sound.
minamp
Sets the amplitude threshold (range 0 to 32767) for the display of partial tracks. Setting a non-zero value excludes low-level components that may be attributable to noise, or artefacts of the analysis. It can also be used to highlight the regions of the brightest timbre in the sound.
maxamp
Sets the maximum amplitude to plot, and hence the scale of the vertical axis.

Note:  this is a required parameter for the 3D plot option only. If not included in the command line (which would therefore require all other optional parameters to be entered), it is asked for interactively.

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Internal commands

When mqplot has obtained all required parameters, it cretaes an eps file (launching GSVIEW or the equivalent), and presents a command prompt. These enable switching between 2d and 3D views, range changes, and (for the 3D plots) re-orientation of the axes.
 
h            :      (help) lists available commands
q or x     :     (quit) (exit)  exit the program
2            :     draw a  2D plot  ( time/ frequency)
3            :      draw a 3D (perspective) plot  ( time/ frequency/amplitude)
                        requires an updated maxamp value each time
A           :       change display angles (3D only)
requests two parameters, alpha and beta. Values are in degrees. alpha  sets the angle (relative to horizontal) of the time axis. beta sets the angle (relative to the horizontal) of the frequency axis. Although the original documentation stipulates that alpha plus   beta must not exceed 90, it has been found that so long as neither exceeds 90, the program works correctly. Some experimentation is worthwhile here, as the relationship between the given values and the appearance of the resulting display is not always obvious.
   a         :     change amplitude axis (3D only)
   d         :     choose projection trace dots (3D only)
Activates and deactivates projection against the amplitude and frequency axes. Each axis is queried in turn; take care to activate the one you want!
 v or f     :    change frequency scale
enter the new values for minf and maxf (Hz)
 n or b    :    change frame axis
The new start frame, and the number of frames to display, are required. A value for the latter can be found by experiment, or, for an accurate range, refer to the frame duration given in the analysis file header - this is displayed when the program is launched.
   T        :     change time axis
start time and duration (seconds) are required.
   t         :     change amplitude threshold. Corresponds to maxamp.

   u        :      update display

repeat the plot with the current settings, in case you missed it the first time.


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