X-Git-Url: https://scm.cri.ensmp.fr/git/Faustine.git/blobdiff_plain/1059e1cc0c2ecfa237406949aa26155b6a5b9154..66f23d4fabf89ad09adbd4dfc15ac6b5b2b7da83:/interpreter/preprocessor/faust-0.9.47mr3/tools/faust2pd/examples/synth/compressor.dsp

diff --git a/interpreter/preprocessor/faust-0.9.47mr3/tools/faust2pd/examples/synth/compressor.dsp b/interpreter/preprocessor/faust-0.9.47mr3/tools/faust2pd/examples/synth/compressor.dsp
new file mode 100644
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+++ b/interpreter/preprocessor/faust-0.9.47mr3/tools/faust2pd/examples/synth/compressor.dsp
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+
+/* Compressor unit. */
+
+declare name "compressor -- compressor/limiter unit";
+declare author "Albert Graef";
+declare version "1.0";
+
+import("music.lib");
+
+/* Controls. */
+
+// partition the controls into these three groups
+comp_group(x)	= hgroup("1-compression", x);
+env_group(x)	= vgroup("2-envelop", x);
+gain_group(x)	= vgroup("3-gain", x);
+
+// compressor controls: ratio, threshold and knee size
+ratio		= comp_group(nentry("ratio", 2, 1, 20, 0.1));
+threshold	= comp_group(nentry("threshold", -20, -96, 10, 0.1));
+knee		= comp_group(nentry("knee", 3, 0, 20, 0.1));
+
+// attack and release controls; clamped to a minimum of 1 sample
+attack		= env_group(hslider("attack", 0.002, 0, 1, 0.001)) : max(1/SR);
+release		= env_group(hslider("release", 0.5, 0, 10, 0.01)) : max(1/SR);
+
+// gain controls: make-up gain, compression gain meter
+makeup_gain	= gain_group(hslider("makeup gain", 0, -96, 96, 0.1));
+gain(x)		= attach(x, x : gain_group(hbargraph("gain", -96, 0)));
+
+/* Envelop detector. This is basically the same as in amp.dsp. */
+
+t		= 0.1;
+g		= exp(-1/(SR*t));
+env		= abs : *(1-g) : + ~ *(g);
+rms		= sqr : *(1-g) : + ~ *(g) : sqrt;
+sqr(x)		= x*x;
+
+/* Compute the envelop of a stereo signal. Replace env with rms if you want to
+   use the RMS value instead. */
+
+env2(x,y)	= max(env(x),env(y));
+
+/* Compute the compression factor for the current input level. The gain is
+   always 0 dB if we're below the reduced threshold, threshold-knee. Beyond
+   the real threshold value the level is scaled by 1/ratio. Between these two
+   extremes we return a convex combination of those factors. This is also
+   known as "soft-knee" compression: the compression kicks in gradually at
+   threshold-knee and reaches its full value at threshold. For special
+   effects, you can also achieve old-school "hard-knee" compression by setting
+   the knee value to zero. Also note that, before computing the gain, the
+   input level is first smoothed out using a 1 pole IIR to prevent clicks when
+   the input level changes abruptly. The attack and release times of this
+   filter are configured with the corresponding envelop controls of the
+   compressor. */
+
+compress(env)	= level*(1-r)/r
+with {
+	// the (filtered) input level above the threshold
+	level	= env : h ~ _ : linear2db : (_-threshold+knee) : max(0)
+	with {
+		h(x,y)	= f*x+(1-f)*y with { f = (x<y)*ga+(x>=y)*gr; };
+		ga	= exp(-1/(SR*attack));
+		gr	= exp(-1/(SR*release));
+	};
+	// the knee factor, clamped to 0..1; we add a small perturbation in
+	// the denominator to prevent infinities and nan when knee<<1
+	p	= level/(knee+eps) : max(0) : min(1) with { eps = 0.001; };
+	// the actual compression ratio
+	r	= 1-p+p*ratio;
+};
+
+process(x,y)	= (g*x,g*y)
+with {
+	g	= env2(x,y) : compress : gain : +(makeup_gain) : db2linear;
+};