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// This file is part of the 64k demo project.
// It implements the multi-voice additive synthesis engine.
// Supports real-time spectrogram updates and peak detection.
#include "synth.h"
#include "audio/dct.h"
#include "audio/window.h"
#include <atomic>
#include <math.h>
#include <stdio.h> // For printf
#include <string.h> // For memset
struct Voice {
bool active;
int spectrogram_id;
float volume;
float pan_left;
float pan_right;
int current_spectral_frame;
int total_spectral_frames;
float time_domain_buffer[DCT_SIZE];
int buffer_pos;
const volatile float *active_spectral_data;
};
static struct {
Spectrogram spectrograms[MAX_SPECTROGRAMS];
const volatile float *active_spectrogram_data[MAX_SPECTROGRAMS];
bool spectrogram_registered[MAX_SPECTROGRAMS];
} g_synth_data;
static Voice g_voices[MAX_VOICES];
static volatile float g_current_output_peak = 0.0f; // Global peak for visualization
static float g_hamming_window[WINDOW_SIZE]; // Static window for optimization
void synth_init() {
memset(&g_synth_data, 0, sizeof(g_synth_data));
memset(g_voices, 0, sizeof(g_voices));
g_current_output_peak = 0.0f;
// Initialize the Hamming window once
hamming_window_512(g_hamming_window);
}
void synth_shutdown() {
// Nothing to do here since we are not allocating memory
}
int synth_register_spectrogram(const Spectrogram *spec) {
for (int i = 0; i < MAX_SPECTROGRAMS; ++i) {
if (!g_synth_data.spectrogram_registered[i]) {
g_synth_data.spectrograms[i] = *spec;
g_synth_data.active_spectrogram_data[i] = spec->spectral_data_a;
g_synth_data.spectrogram_registered[i] = true;
return i;
}
}
return -1; // No free slots
}
void synth_unregister_spectrogram(int spectrogram_id) {
if (spectrogram_id >= 0 && spectrogram_id < MAX_SPECTROGRAMS) {
g_synth_data.spectrogram_registered[spectrogram_id] = false;
}
}
float *synth_begin_update(int spectrogram_id) {
if (spectrogram_id < 0 || spectrogram_id >= MAX_SPECTROGRAMS ||
!g_synth_data.spectrogram_registered[spectrogram_id]) {
return nullptr;
}
const volatile float *active_ptr =
g_synth_data.active_spectrogram_data[spectrogram_id];
if (active_ptr == g_synth_data.spectrograms[spectrogram_id].spectral_data_a) {
return const_cast<float *>(
g_synth_data.spectrograms[spectrogram_id].spectral_data_b);
} else {
return const_cast<float *>(
g_synth_data.spectrograms[spectrogram_id].spectral_data_a);
}
}
void synth_commit_update(int spectrogram_id) {
if (spectrogram_id < 0 || spectrogram_id >= MAX_SPECTROGRAMS ||
!g_synth_data.spectrogram_registered[spectrogram_id]) {
return;
}
const volatile float *old_active_ptr =
g_synth_data.active_spectrogram_data[spectrogram_id];
const float *new_active_ptr =
(old_active_ptr ==
g_synth_data.spectrograms[spectrogram_id].spectral_data_a)
? g_synth_data.spectrograms[spectrogram_id].spectral_data_b
: g_synth_data.spectrograms[spectrogram_id].spectral_data_a;
// Atomic swap using GCC/Clang builtins for thread safety
__atomic_store_n(
(const float **)&g_synth_data.active_spectrogram_data[spectrogram_id],
new_active_ptr, __ATOMIC_RELEASE);
}
void synth_trigger_voice(int spectrogram_id, float volume, float pan) {
if (spectrogram_id < 0 || spectrogram_id >= MAX_SPECTROGRAMS ||
!g_synth_data.spectrogram_registered[spectrogram_id]) {
return;
}
for (int i = 0; i < MAX_VOICES; ++i) {
if (!g_voices[i].active) {
Voice &v = g_voices[i];
v.active = true;
v.spectrogram_id = spectrogram_id;
v.volume = volume;
// Simple linear panning
v.pan_left = (pan > 0.0f) ? (1.0f - pan) : 1.0f;
v.pan_right = (pan < 0.0f) ? (1.0f + pan) : 1.0f;
v.current_spectral_frame = 0;
v.total_spectral_frames =
g_synth_data.spectrograms[spectrogram_id].num_frames;
v.buffer_pos = DCT_SIZE; // Force IDCT on first render
v.active_spectral_data =
g_synth_data.active_spectrogram_data[spectrogram_id];
return; // Voice triggered
}
}
}
void synth_render(float *output_buffer, int num_frames) {
// Use the pre-calculated window
// float window[WINDOW_SIZE];
// hamming_window_512(window);
// Faster decay for more responsive visuals
g_current_output_peak *= 0.90f;
for (int i = 0; i < num_frames; ++i) {
float left_sample = 0.0f;
float right_sample = 0.0f;
for (int v_idx = 0; v_idx < MAX_VOICES; ++v_idx) {
Voice &v = g_voices[v_idx];
if (!v.active)
continue;
if (v.buffer_pos >= DCT_SIZE) {
if (v.current_spectral_frame >= v.total_spectral_frames) {
v.active = false;
continue;
}
// Fetch the latest active spectrogram pointer for this voice
v.active_spectral_data =
g_synth_data.active_spectrogram_data[v.spectrogram_id];
const float *spectral_frame = (const float *)v.active_spectral_data +
(v.current_spectral_frame * DCT_SIZE);
float windowed_frame[DCT_SIZE];
for (int j = 0; j < DCT_SIZE; ++j) {
windowed_frame[j] = spectral_frame[j] * g_hamming_window[j]; // Use static window
}
idct_512(windowed_frame, v.time_domain_buffer);
v.buffer_pos = 0;
v.current_spectral_frame++;
}
float voice_sample = v.time_domain_buffer[v.buffer_pos] * v.volume;
left_sample += voice_sample * v.pan_left;
right_sample += voice_sample * v.pan_right;
v.buffer_pos++;
}
output_buffer[i * 2] = left_sample;
output_buffer[i * 2 + 1] = right_sample;
// Update the peak with the new max (attack)
g_current_output_peak =
fmaxf(g_current_output_peak,
fmaxf(fabsf(left_sample), fabsf(right_sample)));
}
}
int synth_get_active_voice_count() {
int count = 0;
for (int i = 0; i < MAX_VOICES; ++i) {
if (g_voices[i].active) {
count++;
}
}
return count;
}
float synth_get_output_peak() {
return g_current_output_peak;
}
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