adafruit · gamblor21 · Jan 23, 2025 · Oct 23, 2024 · Oct 31, 2024 · Oct 31, 2024
diff --git a/shared-module/audiodelays/Echo.c b/shared-module/audiodelays/Echo.c
@@ -258,32 +258,6 @@ void common_hal_audiodelays_echo_stop(audiodelays_echo_obj_t *self) {
     return;
 }
 
-#define RANGE_LOW_16 (-28000)
-#define RANGE_HIGH_16 (28000)
-#define RANGE_SHIFT_16 (16)
-#define RANGE_SCALE_16 (0xfffffff / (32768 * 2 - RANGE_HIGH_16)) // 2 for echo+sample
-
-// dynamic range compression via a downward compressor with hard knee
-//
-// When the output value is within the range +-28000 (about 85% of full scale),
-// it is unchanged. Otherwise, it undergoes a gain reduction so that the
-// largest possible values, (+32768,-32767) * 2 (2 for echo and sample),
-// still fit within the output range
-//
-// This produces a much louder overall volume with multiple voices, without
-// much additional processing.
-//
-// https://en.wikipedia.org/wiki/Dynamic_range_compression
-static
-int16_t mix_down_sample(int32_t sample) {
-    if (sample < RANGE_LOW_16) {
-        sample = (((sample - RANGE_LOW_16) * RANGE_SCALE_16) >> RANGE_SHIFT_16) + RANGE_LOW_16;
-    } else if (sample > RANGE_HIGH_16) {
-        sample = (((sample - RANGE_HIGH_16) * RANGE_SCALE_16) >> RANGE_SHIFT_16) + RANGE_HIGH_16;
-    }
-    return sample;
-}
-
 audioio_get_buffer_result_t audiodelays_echo_get_buffer(audiodelays_echo_obj_t *self, bool single_channel_output, uint8_t channel,
     uint8_t **buffer, uint32_t *buffer_length) {
 
@@ -454,7 +428,7 @@ audioio_get_buffer_result_t audiodelays_echo_get_buffer(audiodelays_echo_obj_t *
                     }
 
                     if (MP_LIKELY(self->bits_per_sample == 16)) {
-                        word = mix_down_sample(word);
+                        word = synthio_mix_down_sample(word);
                         if (self->freq_shift) {
                             for (uint32_t j = echo_buffer_pos >> 8; j < next_buffer_pos >> 8; j++) {
                                 echo_buffer[j % echo_buf_len] = (int16_t)word;
@@ -479,7 +453,7 @@ audioio_get_buffer_result_t audiodelays_echo_get_buffer(audiodelays_echo_obj_t *
                     }
 
                     word = echo + sample_word;
-                    word = mix_down_sample(word);
+                    word = synthio_mix_down_sample(word);
 
                     if (MP_LIKELY(self->bits_per_sample == 16)) {
                         word_buffer[i] = (int16_t)((sample_word * (MICROPY_FLOAT_CONST(1.0) - mix)) + (word * mix));

diff --git a/shared-module/audiodelays/Echo.h b/shared-module/audiodelays/Echo.h
@@ -8,6 +8,7 @@
 #include "py/obj.h"
 
 #include "shared-module/audiocore/__init__.h"
+#include "shared-module/synthio/__init__.h"
 #include "shared-module/synthio/block.h"
 
 extern const mp_obj_type_t audiodelays_echo_type;

diff --git a/shared-module/audiofilters/Filter.c b/shared-module/audiofilters/Filter.c
@@ -212,32 +212,6 @@ void common_hal_audiofilters_filter_stop(audiofilters_filter_obj_t *self) {
     return;
 }
 
-#define RANGE_LOW_16 (-28000)
-#define RANGE_HIGH_16 (28000)
-#define RANGE_SHIFT_16 (16)
-#define RANGE_SCALE_16 (0xfffffff / (32768 * 2 - RANGE_HIGH_16)) // 2 for echo+sample
-
-// dynamic range compression via a downward compressor with hard knee
-//
-// When the output value is within the range +-28000 (about 85% of full scale),
-// it is unchanged. Otherwise, it undergoes a gain reduction so that the
-// largest possible values, (+32768,-32767) * 2 (2 for echo and sample),
-// still fit within the output range
-//
-// This produces a much louder overall volume with multiple voices, without
-// much additional processing.
-//
-// https://en.wikipedia.org/wiki/Dynamic_range_compression
-static
-int16_t mix_down_sample(int32_t sample) {
-    if (sample < RANGE_LOW_16) {
-        sample = (((sample - RANGE_LOW_16) * RANGE_SCALE_16) >> RANGE_SHIFT_16) + RANGE_LOW_16;
-    } else if (sample > RANGE_HIGH_16) {
-        sample = (((sample - RANGE_HIGH_16) * RANGE_SCALE_16) >> RANGE_SHIFT_16) + RANGE_HIGH_16;
-    }
-    return sample;
-}
-
 audioio_get_buffer_result_t audiofilters_filter_get_buffer(audiofilters_filter_obj_t *self, bool single_channel_output, uint8_t channel,
     uint8_t **buffer, uint32_t *buffer_length) {
     (void)channel;
@@ -341,7 +315,7 @@ audioio_get_buffer_result_t audiofilters_filter_get_buffer(audiofilters_filter_o
                     // Mix processed signal with original sample and transfer to output buffer
                     for (uint32_t j = 0; j < n_samples; j++) {
                         if (MP_LIKELY(self->bits_per_sample == 16)) {
-                            word_buffer[i + j] = mix_down_sample((int32_t)((sample_src[i + j] * (MICROPY_FLOAT_CONST(1.0) - mix)) + (self->filter_buffer[j] * mix)));
+                            word_buffer[i + j] = synthio_mix_down_sample((int32_t)((sample_src[i + j] * (MICROPY_FLOAT_CONST(1.0) - mix)) + (self->filter_buffer[j] * mix)));
                             if (!self->samples_signed) {
                                 word_buffer[i + j] ^= 0x8000;
                             }

diff --git a/shared-module/audiofilters/Filter.h b/shared-module/audiofilters/Filter.h
@@ -9,6 +9,7 @@
 
 #include "shared-bindings/synthio/Biquad.h"
 #include "shared-module/audiocore/__init__.h"
+#include "shared-module/synthio/__init__.h"
 #include "shared-module/synthio/block.h"
 #include "shared-module/synthio/Biquad.h"
 

diff --git a/shared-module/synthio/__init__.c b/shared-module/synthio/__init__.c
@@ -145,8 +145,7 @@ static synthio_envelope_definition_t *synthio_synth_get_note_envelope(synthio_sy
 // much additional processing.
 //
 // https://en.wikipedia.org/wiki/Dynamic_range_compression
-static
-int16_t mix_down_sample(int32_t sample) {
+int16_t synthio_mix_down_sample(int32_t sample) {
     if (sample < RANGE_LOW) {
         sample = (((sample - RANGE_LOW) * RANGE_SCALE) >> RANGE_SHIFT) + RANGE_LOW;
     } else if (sample > RANGE_HIGH) {
@@ -345,7 +344,7 @@ void synthio_synth_synthesize(synthio_synth_t *synth, uint8_t **bufptr, uint32_t
     // mix down audio
     for (size_t i = 0; i < dur * synth->channel_count; i++) {
         int32_t sample = out_buffer32[i];
-        out_buffer16[i] = mix_down_sample(sample);
+        out_buffer16[i] = synthio_mix_down_sample(sample);
     }
 
     // advance envelope states

diff --git a/shared-module/synthio/__init__.h b/shared-module/synthio/__init__.h
@@ -79,6 +79,8 @@ bool synthio_span_change_note(synthio_synth_t *synth, mp_obj_t old_note, mp_obj_
 void synthio_envelope_step(synthio_envelope_definition_t *definition, synthio_envelope_state_t *state, int n_samples);
 void synthio_envelope_definition_set(synthio_envelope_definition_t *envelope, mp_obj_t obj, uint32_t sample_rate);
 
+int16_t synthio_mix_down_sample(int32_t sample);
+
 uint64_t synthio_frequency_convert_float_to_scaled(mp_float_t frequency_hz);
 uint32_t synthio_frequency_convert_float_to_dds(mp_float_t frequency_hz, int32_t sample_rate);
 uint32_t synthio_frequency_convert_scaled_to_dds(uint64_t frequency_scaled, int32_t sample_rate);