X-Git-Url: https://main.carlh.net/gitweb/?a=blobdiff_plain;f=libs%2Fardour%2Fardour%2Fdsp_filter.h;h=994d8725ea418576c6c3edacfacd779f49f8dcb1;hb=02db39c1bc63da52c21d77cc8f840d5d3233f301;hp=0ecf08cf44f1752e164e9d57807e8175d11e8853;hpb=581e25f3699132628785943e770c2653f5d09efc;p=ardour.git

diff --git a/libs/ardour/ardour/dsp_filter.h b/libs/ardour/ardour/dsp_filter.h
index 0ecf08cf44..994d8725ea 100644
--- a/libs/ardour/ardour/dsp_filter.h
+++ b/libs/ardour/ardour/dsp_filter.h
@@ -27,18 +27,20 @@
 
 namespace ARDOUR { namespace DSP {
 
-	/** C Shared Memory
+	/** C/C++ Shared Memory
 	 *
-	 * A convenience class representing a C array or float[] or int32_t[]
+	 * A convenience class representing a C array of float[] or int32_t[]
 	 * data values. This is useful for lua scripts to perform DSP operations
-	 * directly using C, C++.
-	 * Access to this memory area is always 4 byte aligned: float, int.
+	 * directly using C/C++ with CPU Hardware acceleration.
 	 *
-	 * This memory area can also be shared between different instances.
+	 * Access to this memory area is always 4 byte aligned. The data
+	 * is interpreted either as float or as int.
+	 *
+	 * This memory area can also be shared between different instances
+	 * or the same lua plugin (DSP, GUI).
 	 *
 	 * Since memory allocation is not realtime safe it should be
 	 * allocated during dsp_init() or dsp_configure().
-	 *
 	 * The memory is free()ed automatically when the lua instance is
 	 * destroyed.
 	 */
@@ -191,7 +193,7 @@ namespace ARDOUR { namespace DSP {
 	};
 
 	/** Biquad Filter */
-	class LIBARDOUR_API BiQuad {
+	class LIBARDOUR_API Biquad {
 		public:
 			enum Type {
 				LowPass,
@@ -209,8 +211,8 @@ namespace ARDOUR { namespace DSP {
 			 *
 			 * @param samplerate Samplerate
 			 */
-			BiQuad (double samplerate);
-			BiQuad (const BiQuad &other);
+			Biquad (double samplerate);
+			Biquad (const Biquad &other);
 
 			/** process audio data
 			 *
@@ -220,12 +222,19 @@ namespace ARDOUR { namespace DSP {
 			void run (float *data, const uint32_t n_samples);
 			/** setup filter, compute coefficients
 			 *
-			 * @param t filter type
+			 * @param t filter type (LowPass, HighPass, etc)
 			 * @param freq filter frequency
 			 * @param Q filter quality
 			 * @param gain filter gain
 			 */
 			void compute (Type t, double freq, double Q, double gain);
+
+			/** filter transfer function (filter response for spectrum visualization)
+			 * @param freq frequency
+			 * @return gain at given frequency in dB (clamped to -120..+120)
+			 */
+			float dB_at_freq (float freq) const;
+
 			/** reset filter state */
 			void reset () { _z1 = _z2 = 0.0; }
 		private: