The benefit of the C-language implementation is that C-SPAN programs can make use of all the facilities of the C language in addition to the commands provided by C_SPAN which are detailed below. Thus a C-SPAN program can use global and local variables, call sub-routines and use the C pre-processor to modify the command language.
/* comments */
SYNTH()
{
/* parameter settings in here */
}
LENGTH(t) This sets the overall length of the synthesis to t milliseconds. The default length is taken from the lastest time at which an assignment is made. You need this command if modifications to a synthesis reduce its length.
CLEAR This clears the entire synthesis table, and resets the start time and end times to zero.
FLUSH This command forces construction of the synthesizer parameter table at this point in the specification. The synthesizer parameter table is constructed automatically at the end of the SYNTH() routine, so you only need this command if your program builds more than one synthesis.
SAVE This command saves the current time position in the synthesis on an internal stack. Since all settings of AT(t) and WAIT(t) affect the current time position, regardless of whether they are made in SYNTH() or in a subroutine, you may need to save the current time to make local parameter settings and then restore it.
RESTORE This command restores the last current time position save with SAVE.
FX(v,i) Fundamental frequency (Hz).
F1(v,i) Frequency of formant 1 (Hz).
A1(v,i) Amplitude of formant 1 (dB).
F2(v,i) Frequency of formant 2 (Hz).
A2(v,i) Amplitude of formant 2 (dB).
F3(v,i) Frequency of formant 3 (Hz).
A3(v,i) Amplitude of formant 3 (dB).
F4(v,i) Frequency of formant 4 (Hz).
A4(v,i) Amplitude of formant 4 (dB).
FN(v,i) Frequency of nasal formant (Hz).
AN(v,i) Amplitude of nasal formant (dB).
VR(v,i) Voicing ratio, in range 0(unvoiced) to 248(voiced).
and where <value> is a decimal number representing the value to which to set the control parameter at the current time. The value NUL can be used to signify that no change to the currently specified value at this position is requested (if only the interpolation type was to be changed, for example).
The parameter <interpolation> is from this list:
FIX Set value at this time with no interpolation.
LIN Set value at this time and interpolate to the first subsequent specification for this parameter. Interpolations are actually performed after all specifications are made, so you do not need to specify the end value of the interpolation before the start value.
LOG Set value at this time and logarithmically interpolate to the first subsequent setting of this parameter.
NUL Make no changes to the interpolation setting currently specified at this time position.
In addition to these parameter settings the command GET(p,t) returns the value of parameter p (FX,F1, etc) at time t. The global variable NOW contains the current time position. This command does not make any changes to the parameter table. If you request the value of a parameter in an interpolated region, GET returns the interpolated value using the current specifications for the start and end points.
There is no range checking on the values used in these parameter settings. The allowed ranges will depend on the formant synthesizer that you will be using to make the synthetic speech. Similarly, some synthesizers may not make use of all the parameters (e.g. the JSRU system has a fixed F4 and AN is linked to A1). There is no synthesizer specific code in the C-SPAN language.
AT(t) Set the current time position in the synthesis to absolute t milliseconds. Only one current time position is maintained globally, so be careful of constructions such as:
AT(100);
rampamplitudes();
FX(90,FIX); /* does NOT change FX at time 100 */
:
:
rampamplitudes()
{
A1(NUL,LIN); A2(NUL,LIN); A3(NUL,LIN);
WAIT(50);
A1(0,FIX); A2(0,FIX); A3(0,FIX);
}
Use the SAVE and RESTORE commands within subroutines to preserve the current
time position outside the routine.
WAIT(t) Move the current time position on by t milliseconds.
The global variable NOW contains the current time position.
/* test.spn - demonstration C-SPAN program */
#define SILENCE A1(0,LIN);A2(0,LIN);A3(0,LIN);A4(0,LIN);AN(0,LIN);
SYNTH()
{
/* Synthesis 0 */
AT(0);
/* set up central vowel */
FX(120,LOG); VR(248,LIN);
F1(500,LIN); F2(1000,LIN); F3(1500,LIN);
SILENCE;
WAIT(50);
/* ramp up amplitudes */
A1(40,FIX); A2(35,FIX); A3(30,FIX); AN(GET(A1,NOW),FIX);
AT(500);
/* ramp down amplitudes */
A1(NUL,LIN); A2(NUL,LIN); A3(NUL,LIN); AN(NUL,LIN);
WAIT(50);
/* end at /i/ vowel */
FX(90,FIX);
F1(250,FIX); F2(2500,FIX); F3(3300,FIX);
SILENCE;
/* make this synthesis */
FLUSH;
/* Synthesis 1 */
AT(550);
/* change end to /a/ vowel */
F1(600,FIX); F2(750,FIX); F3(2500,FIX);
/* and re-make it */
FLUSH;
}
1.0 Mark Huckvale