Add loop_start and loop_end properties to synthio.Note for waveshaping and sampling capabilities.

shared-bindings/synthio/Note.c

@@ -45,6 +45,8 @@ static const mp_arg_t note_properties[] = {
     { 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 } },
+    { MP_QSTR_loop_start, MP_ARG_OBJ, {.u_obj = MP_ROM_INT(0) } },
+    { MP_QSTR_loop_end, MP_ARG_OBJ, {.u_obj = MP_ROM_INT(0) } },
 };
 //| class Note:
 //|     def __init__(
@@ -60,6 +62,8 @@ static const mp_arg_t note_properties[] = {
 //|         ring_frequency: float = 0.0,
 //|         ring_bend: float = 0.0,
 //|         ring_waveform: Optional[ReadableBuffer] = 0.0,
+//|         loop_start: int = 0,
+//|         loop_end: int = 0,
 //|     ) -> None:
 //|         """Construct a Note object, with a frequency in Hz, and optional panning, waveform, envelope, tremolo (volume change) and bend (frequency change).
 //|
@@ -296,6 +300,43 @@ MP_PROPERTY_GETSET(synthio_note_ring_waveform_obj,
     (mp_obj_t)&synthio_note_get_ring_waveform_obj,
     (mp_obj_t)&synthio_note_set_ring_waveform_obj);
 
+//|     loop_start: int
+//|     """The index of where to begin looping waveform data. Must be greater than 0 and less than the total size of the waveform data."""
+STATIC mp_obj_t synthio_note_get_loop_start(mp_obj_t self_in) {
+    synthio_note_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    return mp_obj_new_int(common_hal_synthio_note_get_loop_start(self));
+}
+MP_DEFINE_CONST_FUN_OBJ_1(synthio_note_get_loop_start_obj, synthio_note_get_loop_start);
+
+STATIC mp_obj_t synthio_note_set_loop_start(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_loop_start(self, mp_obj_get_int(arg));
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(synthio_note_set_loop_start_obj, synthio_note_set_loop_start);
+MP_PROPERTY_GETSET(synthio_note_loop_start_obj,
+    (mp_obj_t)&synthio_note_get_loop_start_obj,
+    (mp_obj_t)&synthio_note_set_loop_start_obj);
+
+//|     loop_end: int
+//|     """The index of where to end looping waveform data. Must be greater than 0 or ``loop_start`` and less than the total size of the waveform data."""
+//|
+STATIC mp_obj_t synthio_note_get_loop_end(mp_obj_t self_in) {
+    synthio_note_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    return mp_obj_new_int(common_hal_synthio_note_get_loop_end(self));
+}
+MP_DEFINE_CONST_FUN_OBJ_1(synthio_note_get_loop_end_obj, synthio_note_get_loop_end);
+
+STATIC mp_obj_t synthio_note_set_loop_end(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_loop_end(self, mp_obj_get_int(arg));
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(synthio_note_set_loop_end_obj, synthio_note_set_loop_end);
+MP_PROPERTY_GETSET(synthio_note_loop_end_obj,
+    (mp_obj_t)&synthio_note_get_loop_end_obj,
+    (mp_obj_t)&synthio_note_set_loop_end_obj);
+
 
 
 static void note_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
@@ -314,6 +355,8 @@ STATIC const mp_rom_map_elem_t synthio_note_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_ring_frequency), MP_ROM_PTR(&synthio_note_ring_frequency_obj) },
     { MP_ROM_QSTR(MP_QSTR_ring_bend), MP_ROM_PTR(&synthio_note_ring_bend_obj) },
     { MP_ROM_QSTR(MP_QSTR_ring_waveform), MP_ROM_PTR(&synthio_note_ring_waveform_obj) },
+    { MP_ROM_QSTR(MP_QSTR_loop_start), MP_ROM_PTR(&synthio_note_loop_start_obj) },
+    { MP_ROM_QSTR(MP_QSTR_loop_end), MP_ROM_PTR(&synthio_note_loop_end_obj) },
 };
 STATIC MP_DEFINE_CONST_DICT(synthio_note_locals_dict, synthio_note_locals_dict_table);
 

shared-bindings/synthio/Note.h

@@ -35,3 +35,9 @@ void common_hal_synthio_note_set_ring_waveform(synthio_note_obj_t *self, mp_obj_
 
 mp_obj_t common_hal_synthio_note_get_envelope_obj(synthio_note_obj_t *self);
 void common_hal_synthio_note_set_envelope(synthio_note_obj_t *self, mp_obj_t value);
+
+mp_int_t common_hal_synthio_note_get_loop_start(synthio_note_obj_t *self);
+void common_hal_synthio_note_set_loop_start(synthio_note_obj_t *self, mp_int_t value_in);
+
+mp_int_t common_hal_synthio_note_get_loop_end(synthio_note_obj_t *self);
+void common_hal_synthio_note_set_loop_end(synthio_note_obj_t *self, mp_int_t value_in);

shared-module/synthio/Note.c

@@ -135,6 +135,24 @@ void common_hal_synthio_note_set_ring_waveform(synthio_note_obj_t *self, mp_obj_
     self->ring_waveform_obj = ring_waveform_in;
 }
 
+mp_int_t common_hal_synthio_note_get_loop_start(synthio_note_obj_t *self) {
+    return self->loop_start;
+}
+
+void common_hal_synthio_note_set_loop_start(synthio_note_obj_t *self, mp_int_t value_in) {
+    mp_int_t val = mp_arg_validate_int_range(value_in, 0, 32767, MP_QSTR_loop_start);
+    self->loop_start = val;
+}
+
+mp_int_t common_hal_synthio_note_get_loop_end(synthio_note_obj_t *self) {
+    return self->loop_end;
+}
+
+void common_hal_synthio_note_set_loop_end(synthio_note_obj_t *self, mp_int_t value_in) {
+    mp_int_t val = mp_arg_validate_int_range(value_in, 0, 32767, MP_QSTR_loop_end);
+    self->loop_end = val;
+}
+
 void synthio_note_recalculate(synthio_note_obj_t *self, int32_t sample_rate) {
     if (sample_rate == self->sample_rate) {
         return;

shared-module/synthio/Note.h

@@ -50,6 +50,8 @@ typedef struct synthio_note_obj {
     mp_buffer_info_t waveform_buf;
     mp_buffer_info_t ring_waveform_buf;
     synthio_envelope_definition_t envelope_def;
+
+    uint32_t loop_start, loop_end;
 } synthio_note_obj_t;
 
 void synthio_note_recalculate(synthio_note_obj_t *self, int32_t sample_rate);

shared-module/synthio/__init__.c

@@ -180,6 +180,7 @@ static bool synth_note_into_buffer(synthio_synth_t *synth, int chan, int32_t *ou
 
     uint32_t dds_rate;
     const int16_t *waveform = synth->waveform_bufinfo.buf;
+    uint32_t waveform_start = 0;
     uint32_t waveform_length = synth->waveform_bufinfo.len;
 
     uint32_t ring_dds_rate = 0;
@@ -202,8 +203,14 @@ static bool synth_note_into_buffer(synthio_synth_t *synth, int chan, int32_t *ou
         if (note->waveform_buf.buf) {
             waveform = note->waveform_buf.buf;
             waveform_length = note->waveform_buf.len;
+            if (note->loop_start > 0 && note->loop_start < waveform_length) {
+                waveform_start = note->loop_start;
             }
-        dds_rate = synthio_frequency_convert_scaled_to_dds((uint64_t)frequency_scaled * waveform_length, sample_rate);
+            if (note->loop_end > waveform_start && note->loop_end < waveform_length) {
+                waveform_length = note->loop_end;
+            }
+        }
+        dds_rate = synthio_frequency_convert_scaled_to_dds((uint64_t)frequency_scaled * (waveform_length - waveform_start), sample_rate);
         if (note->ring_frequency_scaled != 0 && note->ring_waveform_buf.buf) {
             ring_waveform = note->ring_waveform_buf.buf;
             ring_waveform_length = note->ring_waveform_buf.len;
@@ -215,6 +222,7 @@ static bool synth_note_into_buffer(synthio_synth_t *synth, int chan, int32_t *ou
         }
     }
 
+    uint32_t offset = waveform_start << SYNTHIO_FREQUENCY_SHIFT;
     uint32_t lim = waveform_length << SYNTHIO_FREQUENCY_SHIFT;
     uint32_t accum = synth->accum[chan];
 
@@ -225,7 +233,7 @@ static bool synth_note_into_buffer(synthio_synth_t *synth, int chan, int32_t *ou
 
     // can happen if note waveform gets set mid-note, but the expensive modulo is usually avoided
     if (accum > lim) {
-        accum %= lim;
+        accum = accum % lim + offset;
     }
 
     // first, fill with waveform
@@ -233,7 +241,7 @@ static bool synth_note_into_buffer(synthio_synth_t *synth, int chan, int32_t *ou
         accum += dds_rate;
         // because dds_rate is low enough, the subtraction is guaranteed to go back into range, no expensive modulo needed
         if (accum > lim) {
-            accum -= lim;
+            accum = accum - lim + offset;
         }
         int16_t idx = accum >> SYNTHIO_FREQUENCY_SHIFT;
         out_buffer32[i] = waveform[idx];