Synthio: switch to per-note biquad filtering

ports/unix/variants/coverage/mpconfigvariant.mk

@@ -45,6 +45,7 @@ SRC_BITMAP := \
 	shared-bindings/synthio/MidiTrack.c \
 	shared-bindings/synthio/LFO.c \
 	shared-bindings/synthio/Note.c \
+	shared-bindings/synthio/Biquad.c \
 	shared-bindings/synthio/Synthesizer.c \
 	shared-bindings/traceback/__init__.c \
 	shared-bindings/util.c \
@@ -70,6 +71,7 @@ SRC_BITMAP := \
 	shared-module/synthio/MidiTrack.c \
 	shared-module/synthio/LFO.c \
 	shared-module/synthio/Note.c \
+	shared-module/synthio/Biquad.c \
 	shared-module/synthio/Synthesizer.c \
 	shared-module/traceback/__init__.c \
 	shared-module/zlib/__init__.c \

py/circuitpy_defns.mk

@@ -650,6 +650,7 @@ SRC_SHARED_MODULE_ALL = \
 	struct/__init__.c \
 	supervisor/__init__.c \
 	supervisor/StatusBar.c \
+	synthio/Biquad.c \
 	synthio/LFO.c \
 	synthio/Math.c \
 	synthio/MidiTrack.c \

shared-bindings/synthio/Biquad.c

@@ -0,0 +1,110 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Artyom Skrobov
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <math.h>
+#include <string.h>
+
+#include "py/enum.h"
+#include "py/mperrno.h"
+#include "py/obj.h"
+#include "py/objnamedtuple.h"
+#include "py/runtime.h"
+
+#include "shared-bindings/synthio/__init__.h"
+#include "shared-bindings/synthio/LFO.h"
+#include "shared-bindings/synthio/Math.h"
+#include "shared-bindings/synthio/MidiTrack.h"
+#include "shared-bindings/synthio/Note.h"
+#include "shared-bindings/synthio/Synthesizer.h"
+
+#include "shared-module/synthio/LFO.h"
+
+#define default_attack_time (MICROPY_FLOAT_CONST(0.1))
+#define default_decay_time (MICROPY_FLOAT_CONST(0.05))
+#define default_release_time (MICROPY_FLOAT_CONST(0.2))
+#define default_attack_level (MICROPY_FLOAT_CONST(1.))
+#define default_sustain_level (MICROPY_FLOAT_CONST(0.8))
+
+static const mp_arg_t biquad_properties[] = {
+    { MP_QSTR_a1, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_obj = MP_ROM_NONE} },
+    { MP_QSTR_a2, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_obj = MP_ROM_NONE} },
+    { MP_QSTR_b0, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_obj = MP_ROM_NONE} },
+    { MP_QSTR_b1, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_obj = MP_ROM_NONE} },
+    { MP_QSTR_b2, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_obj = MP_ROM_NONE} },
+};
+
+//| class Biquad:
+//|     def __init__(self, b0: float, b1: float, b2: float, a1: float, a2: float) -> None:
+//|         """Construct a normalized biquad filter object.
+//|
+//|         This implements the "direct form 1" biquad filter, where each coefficient
+//|         has been pre-divided by a0.
+//|
+//|         Biquad objects are usually constructed via one of the related methods on a `Synthesizer` object
+//|         rather than directly from coefficients.
+//|
+//|         https://github.com/WebAudio/Audio-EQ-Cookbook/blob/main/Audio-EQ-Cookbook.txt
+//|         """
+//|
+STATIC mp_obj_t synthio_biquad_make_new(const mp_obj_type_t *type_in, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
+    mp_arg_val_t args[MP_ARRAY_SIZE(biquad_properties)];
+    mp_arg_parse_all_kw_array(n_args, n_kw, all_args, MP_ARRAY_SIZE(biquad_properties), biquad_properties, args);
+
+    for (size_t i = 0; i < MP_ARRAY_SIZE(biquad_properties); i++) {
+        args[i].u_obj = mp_obj_new_float(mp_arg_validate_type_float(args[i].u_obj, biquad_properties[i].qst));
+    }
+
+    MP_STATIC_ASSERT(sizeof(mp_arg_val_t) == sizeof(mp_obj_t));
+    return namedtuple_make_new(type_in, MP_ARRAY_SIZE(args), 0, &args[0].u_obj);
+}
+
+const mp_obj_namedtuple_type_t synthio_biquad_type_obj = {
+    .base = {
+        .base = {
+            .type = &mp_type_type
+        },
+        .flags = MP_TYPE_FLAG_EXTENDED,
+        .name = MP_QSTR_Biquad,
+        .print = namedtuple_print,
+        .parent = &mp_type_tuple,
+        .make_new = synthio_biquad_make_new,
+        .attr = namedtuple_attr,
+        MP_TYPE_EXTENDED_FIELDS(
+            .unary_op = mp_obj_tuple_unary_op,
+            .binary_op = mp_obj_tuple_binary_op,
+            .subscr = mp_obj_tuple_subscr,
+            .getiter = mp_obj_tuple_getiter,
+            ),
+    },
+    .n_fields = 5,
+    .fields = {
+        MP_QSTR_a1,
+        MP_QSTR_a2,
+        MP_QSTR_b0,
+        MP_QSTR_b1,
+        MP_QSTR_b2,
+    },
+};

shared-bindings/synthio/Biquad.h

@@ -0,0 +1,9 @@
+#pragma once
+
+#include "py/obj.h"
+#include "py/objnamedtuple.h"
+
+extern const mp_obj_namedtuple_type_t synthio_biquad_type_obj;
+mp_obj_t common_hal_synthio_new_lpf(mp_float_t w0, mp_float_t Q);
+mp_obj_t common_hal_synthio_new_hpf(mp_float_t w0, mp_float_t Q);
+mp_obj_t common_hal_synthio_new_bpf(mp_float_t w0, mp_float_t Q);

shared-bindings/synthio/Note.c

@@ -41,7 +41,7 @@ static const mp_arg_t note_properties[] = {
     { MP_QSTR_bend, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_INT(0) } },
     { MP_QSTR_waveform, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_NONE } },
     { MP_QSTR_envelope, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_NONE } },
-    { MP_QSTR_filter, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_INT(1) } },
+    { MP_QSTR_filter, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_NONE } },
     { MP_QSTR_ring_frequency, MP_ARG_OBJ, {.u_obj = MP_ROM_INT(0) } },
     { MP_QSTR_ring_bend, MP_ARG_OBJ, {.u_obj = MP_ROM_INT(0) } },
     { MP_QSTR_ring_waveform, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = MP_ROM_NONE } },
@@ -56,6 +56,7 @@ static const mp_arg_t note_properties[] = {
 //|         envelope: Optional[Envelope] = None,
 //|         amplitude: BlockInput = 0.0,
 //|         bend: BlockInput = 0.0,
+//|         filter: Optional[Biquad] = None,
 //|         ring_frequency: float = 0.0,
 //|         ring_bend: float = 0.0,
 //|         ring_waveform: Optional[ReadableBuffer] = 0.0,
@@ -97,17 +98,21 @@ MP_PROPERTY_GETSET(synthio_note_frequency_obj,
     (mp_obj_t)&synthio_note_get_frequency_obj,
     (mp_obj_t)&synthio_note_set_frequency_obj);
 
-//|     filter: bool
-//|     """True if the note should be processed via the synthesizer's FIR filter."""
+//|     filter: Optional[Biquad]
+//|     """If not None, the output of this Note is filtered according to the provided coefficients.
+//|
+//|     Construct an appropriate filter by calling a filter-making method on the
+//|     `Synthesizer` object where you plan to play the note, as filter coefficients depend
+//|     on the sample rate"""
 STATIC mp_obj_t synthio_note_get_filter(mp_obj_t self_in) {
     synthio_note_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    return mp_obj_new_bool(common_hal_synthio_note_get_filter(self));
+    return common_hal_synthio_note_get_filter_obj(self);
 }
 MP_DEFINE_CONST_FUN_OBJ_1(synthio_note_get_filter_obj, synthio_note_get_filter);
 
 STATIC mp_obj_t synthio_note_set_filter(mp_obj_t self_in, mp_obj_t arg) {
     synthio_note_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    common_hal_synthio_note_set_filter(self, mp_obj_is_true(arg));
+    common_hal_synthio_note_set_filter(self, arg);
     return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_2(synthio_note_set_filter_obj, synthio_note_set_filter);

shared-bindings/synthio/Note.h

@@ -9,8 +9,8 @@ typedef enum synthio_bend_mode_e synthio_bend_mode_t;
 mp_float_t common_hal_synthio_note_get_frequency(synthio_note_obj_t *self);
 void common_hal_synthio_note_set_frequency(synthio_note_obj_t *self, mp_float_t value);
 
-bool common_hal_synthio_note_get_filter(synthio_note_obj_t *self);
-void common_hal_synthio_note_set_filter(synthio_note_obj_t *self, bool value);
+mp_obj_t common_hal_synthio_note_get_filter_obj(synthio_note_obj_t *self);
+void common_hal_synthio_note_set_filter(synthio_note_obj_t *self, mp_obj_t biquad);
 
 mp_obj_t common_hal_synthio_note_get_panning(synthio_note_obj_t *self);
 void common_hal_synthio_note_set_panning(synthio_note_obj_t *self, mp_obj_t value);

shared-bindings/synthio/Synthesizer.c

@@ -32,6 +32,7 @@
 #include "py/objproperty.h"
 #include "py/runtime.h"
 #include "shared-bindings/util.h"
+#include "shared-bindings/synthio/Biquad.h"
 #include "shared-bindings/synthio/Synthesizer.h"
 #include "shared-bindings/synthio/LFO.h"
 #include "shared-bindings/synthio/__init__.h"
@@ -52,7 +53,6 @@
 //|         channel_count: int = 1,
 //|         waveform: Optional[ReadableBuffer] = None,
 //|         envelope: Optional[Envelope] = None,
-//|         filter: Optional[ReadableBuffer] = None,
 //|     ) -> None:
 //|         """Create a synthesizer object.
 //|
@@ -65,17 +65,15 @@
 //|         :param int sample_rate: The desired playback sample rate; higher sample rate requires more memory
 //|         :param int channel_count: The number of output channels (1=mono, 2=stereo)
 //|         :param ReadableBuffer waveform: A single-cycle waveform. Default is a 50% duty cycle square wave. If specified, must be a ReadableBuffer of type 'h' (signed 16 bit)
-//|         :param ReadableBuffer filter: Coefficients of an FIR filter to apply to notes with ``filter=True``. If specified, must be a ReadableBuffer of type 'h' (signed 16 bit)
 //|         :param Optional[Envelope] envelope: An object that defines the loudness of a note over time. The default envelope, `None` provides no ramping, voices turn instantly on and off.
 //|         """
 STATIC mp_obj_t synthio_synthesizer_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
-    enum { ARG_sample_rate, ARG_channel_count, ARG_waveform, ARG_envelope, ARG_filter };
+    enum { ARG_sample_rate, ARG_channel_count, ARG_waveform, ARG_envelope };
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_sample_rate, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 11025} },
         { MP_QSTR_channel_count, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 1} },
         { MP_QSTR_waveform, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none } },
         { MP_QSTR_envelope, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none } },
-        { MP_QSTR_filter, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none } },
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all_kw_array(n_args, n_kw, all_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
@@ -87,7 +85,6 @@ STATIC mp_obj_t synthio_synthesizer_make_new(const mp_obj_type_t *type, size_t n
         args[ARG_sample_rate].u_int,
         args[ARG_channel_count].u_int,
         args[ARG_waveform].u_obj,
-        args[ARG_filter].u_obj,
         args[ARG_envelope].u_obj);
 
     return MP_OBJ_FROM_PTR(self);
@@ -292,6 +289,114 @@ MP_PROPERTY_GETTER(synthio_synthesizer_blocks_obj,
 //|     """Maximum polyphony of the synthesizer (read-only class property)"""
 //|
 
+//|     def low_pass_filter(cls, frequency: float, q_factor: float = 0.7071067811865475) -> Biquad:
+//|         """Construct a low-pass filter with the given parameters.
+//|
+//|         ``frequency``, called f0 in the cookbook, is the corner frequency in Hz
+//|         of the filter.
+//|
+//|         ``q_factor``, called ``Q`` in the cookbook.  Controls how peaked the response will be at the cutoff frequency. A large value makes the response more peaked.
+//|         """
+
+enum passfilter_arg_e { ARG_f0, ARG_Q };
+
+// M_PI is not part of the math.h standard and may not be defined
+// And by defining our own we can ensure it uses the correct const format.
+#define MP_PI MICROPY_FLOAT_CONST(3.14159265358979323846)
+
+static const mp_arg_t passfilter_properties[] = {
+    { MP_QSTR_frequency, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_obj = MP_ROM_NONE} },
+    { MP_QSTR_Q, MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL } },
+};
+
+STATIC mp_obj_t synthio_synthesizer_lpf(size_t n_pos, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    mp_arg_val_t args[MP_ARRAY_SIZE(passfilter_properties)];
+
+    mp_obj_t self_in = pos_args[0];
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+
+    mp_arg_parse_all(n_pos - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(passfilter_properties), passfilter_properties, args);
+
+    mp_float_t f0 = mp_arg_validate_type_float(args[ARG_f0].u_obj, MP_QSTR_f0);
+    mp_float_t Q =
+        args[ARG_Q].u_obj == MP_OBJ_NULL ? MICROPY_FLOAT_CONST(0.7071067811865475) :
+        mp_arg_validate_type_float(args[ARG_Q].u_obj, MP_QSTR_Q);
+
+    mp_float_t w0 = f0 / self->synth.sample_rate * 2 * MP_PI;
+
+    return common_hal_synthio_new_lpf(w0, Q);
+
+}
+
+MP_DEFINE_CONST_FUN_OBJ_KW(synthio_synthesizer_lpf_fun_obj, 1, synthio_synthesizer_lpf);
+
+//|     def high_pass_filter(
+//|         cls, frequency: float, q_factor: float = 0.7071067811865475
+//|     ) -> Biquad:
+//|         """Construct a high-pass filter with the given parameters.
+//|
+//|         ``frequency``, called f0 in the cookbook, is the corner frequency in Hz
+//|         of the filter.
+//|
+//|         ``q_factor``, called ``Q`` in the cookbook.  Controls how peaked the response will be at the cutoff frequency. A large value makes the response more peaked.
+//|         """
+
+STATIC mp_obj_t synthio_synthesizer_hpf(size_t n_pos, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    mp_arg_val_t args[MP_ARRAY_SIZE(passfilter_properties)];
+
+    mp_obj_t self_in = pos_args[0];
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+
+    mp_arg_parse_all(n_pos - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(passfilter_properties), passfilter_properties, args);
+
+    mp_float_t f0 = mp_arg_validate_type_float(args[ARG_f0].u_obj, MP_QSTR_f0);
+    mp_float_t Q =
+        args[ARG_Q].u_obj == MP_OBJ_NULL ? MICROPY_FLOAT_CONST(0.7071067811865475) :
+        mp_arg_validate_type_float(args[ARG_Q].u_obj, MP_QSTR_Q);
+
+    mp_float_t w0 = f0 / self->synth.sample_rate * 2 * MP_PI;
+
+    return common_hal_synthio_new_hpf(w0, Q);
+
+}
+
+//|     def band_pass_filter(
+//|         cls, frequency: float, q_factor: float = 0.7071067811865475
+//|     ) -> Biquad:
+//|         """Construct a band-pass filter with the given parameters.
+//|
+//|         ``frequency``, called f0 in the cookbook, is the center frequency in Hz
+//|         of the filter.
+//|
+//|         ``q_factor``, called ``Q`` in the cookbook.  Controls how peaked the response will be at the cutoff frequency. A large value makes the response more peaked.
+//|
+//|         The coefficients are scaled such that the filter has a 0dB peak gain.
+//|         """
+//|
+
+MP_DEFINE_CONST_FUN_OBJ_KW(synthio_synthesizer_hpf_fun_obj, 1, synthio_synthesizer_hpf);
+
+STATIC mp_obj_t synthio_synthesizer_bpf(size_t n_pos, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    mp_arg_val_t args[MP_ARRAY_SIZE(passfilter_properties)];
+
+    mp_obj_t self_in = pos_args[0];
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+
+    mp_arg_parse_all(n_pos - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(passfilter_properties), passfilter_properties, args);
+
+    mp_float_t f0 = mp_arg_validate_type_float(args[ARG_f0].u_obj, MP_QSTR_f0);
+    mp_float_t Q =
+        args[ARG_Q].u_obj == MP_OBJ_NULL ? MICROPY_FLOAT_CONST(0.7071067811865475) :
+        mp_arg_validate_type_float(args[ARG_Q].u_obj, MP_QSTR_Q);
+
+    mp_float_t w0 = f0 / self->synth.sample_rate * 2 * MP_PI;
+
+    return common_hal_synthio_new_bpf(w0, Q);
+
+}
+
+MP_DEFINE_CONST_FUN_OBJ_KW(synthio_synthesizer_bpf_fun_obj, 1, synthio_synthesizer_bpf);
+
 STATIC const mp_rom_map_elem_t synthio_synthesizer_locals_dict_table[] = {
     // Methods
     { MP_ROM_QSTR(MP_QSTR_press), MP_ROM_PTR(&synthio_synthesizer_press_obj) },
@@ -304,6 +409,9 @@ STATIC const mp_rom_map_elem_t synthio_synthesizer_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR___enter__), MP_ROM_PTR(&default___enter___obj) },
     { MP_ROM_QSTR(MP_QSTR___exit__), MP_ROM_PTR(&synthio_synthesizer___exit___obj) },
 
+    { MP_ROM_QSTR(MP_QSTR_low_pass_filter), MP_ROM_PTR(&synthio_synthesizer_lpf_fun_obj) },
+    { MP_ROM_QSTR(MP_QSTR_high_pass_filter), MP_ROM_PTR(&synthio_synthesizer_hpf_fun_obj) },
+    { MP_ROM_QSTR(MP_QSTR_band_pass_filter), MP_ROM_PTR(&synthio_synthesizer_bpf_fun_obj) },
     // Properties
     { MP_ROM_QSTR(MP_QSTR_envelope), MP_ROM_PTR(&synthio_synthesizer_envelope_obj) },
     { MP_ROM_QSTR(MP_QSTR_sample_rate), MP_ROM_PTR(&synthio_synthesizer_sample_rate_obj) },

shared-bindings/synthio/Synthesizer.h

@@ -32,7 +32,7 @@
 extern const mp_obj_type_t synthio_synthesizer_type;
 
 void common_hal_synthio_synthesizer_construct(synthio_synthesizer_obj_t *self,
-    uint32_t sample_rate, int channel_count, mp_obj_t waveform_obj, mp_obj_t filter_obj,
+    uint32_t sample_rate, int channel_count, mp_obj_t waveform_obj,
     mp_obj_t envelope_obj);
 void common_hal_synthio_synthesizer_deinit(synthio_synthesizer_obj_t *self);
 bool common_hal_synthio_synthesizer_deinited(synthio_synthesizer_obj_t *self);

shared-bindings/synthio/__init__.c

@@ -36,6 +36,7 @@
 #include "extmod/vfs_posix.h"
 
 #include "shared-bindings/synthio/__init__.h"
+#include "shared-bindings/synthio/Biquad.h"
 #include "shared-bindings/synthio/LFO.h"
 #include "shared-bindings/synthio/Math.h"
 #include "shared-bindings/synthio/MidiTrack.h"
@@ -310,6 +311,7 @@ MP_DEFINE_CONST_FUN_OBJ_VAR(synthio_lfo_tick_obj, 1, synthio_lfo_tick);
 
 STATIC const mp_rom_map_elem_t synthio_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_synthio) },
+    { MP_ROM_QSTR(MP_QSTR_Biquad), MP_ROM_PTR(&synthio_biquad_type_obj) },
     { MP_ROM_QSTR(MP_QSTR_Math), MP_ROM_PTR(&synthio_math_type) },
     { MP_ROM_QSTR(MP_QSTR_MathOperation), MP_ROM_PTR(&synthio_math_operation_type) },
     { MP_ROM_QSTR(MP_QSTR_MidiTrack), MP_ROM_PTR(&synthio_miditrack_type) },