From 297616c4ff4bbc7aa53c48eceeb5fa73deb0707f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Bourdeauducq?= <sb@m-labs.hk>
Date: Fri, 27 Dec 2024 16:31:44 +0800
Subject: [PATCH] make more generic, independent modulation channels

---
 sndlock.cpp | 46 +++++++++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/sndlock.cpp b/sndlock.cpp
index 27db760..162762b 100644
--- a/sndlock.cpp
+++ b/sndlock.cpp
@@ -11,16 +11,14 @@
 #include "imgui_impl_glfw.h"
 #include "imgui_impl_opengl3.h"
 
-static std::atomic<bool> shutdown_threads;
-static std::atomic<float> frequency = 440.0f;
-
-#define SND_SIG 1
 #define SND_BITS 16
 #define SND_PCHAN 2
-#define SND_RCHAN 1
 #define SND_RATE 44100
 #define SND_BUFLEN 4096
 
+static std::atomic<bool> shutdown_threads;
+static std::atomic<float> frequency[SND_PCHAN];
+
 static void dsp_thread()
 {
     struct sio_hdl *hdl;
@@ -32,10 +30,10 @@ static void dsp_thread()
         return;
     }
     sio_initpar(&par);
-    par.sig = SND_SIG;
+    par.sig = 1;
     par.bits = SND_BITS;
     par.pchan = SND_PCHAN;
-    par.pchan = SND_RCHAN;
+    par.rchan = 1;
     par.rate = SND_RATE;
     par.le = SIO_LE_NATIVE;
     par.xrun = SIO_ERROR;
@@ -56,7 +54,7 @@ static void dsp_thread()
         return;
     }
 
-    uint32_t phase = 0;
+    uint32_t phase_out[SND_PCHAN] = { 0 };
 
     int16_t buf_out[SND_BUFLEN*SND_PCHAN];
     size_t buf_out_idx = SND_BUFLEN*SND_PCHAN;
@@ -68,13 +66,18 @@ static void dsp_thread()
         poll(pfd, nfds, INFTIM);
         int revents = sio_revents(hdl, pfd);
 
+        uint32_t ftw[SND_PCHAN];
+        for(int i=0;i<SND_PCHAN;i++)
+            ftw[i] = frequency[i]*(float)UINT32_MAX/SND_RATE;
+
         if(revents & POLLOUT) {
+            float scale = powf(2.0f, SND_BITS-1) - 1.0f;
             if(buf_out_idx == SND_BUFLEN*SND_PCHAN) {
-                uint32_t ftw = frequency*(float)UINT32_MAX/SND_RATE;
-                for(int i=0;i<SND_BUFLEN;i++) {
-                    buf_out[2*i] = buf_out[2*i+1] = (INT16_MAX-1)*sinf(phase*2.0f*(float)M_PI/(float)UINT32_MAX);
-                    phase += ftw;
-                }
+                for(int i=0;i<SND_PCHAN;i++)
+                    for(int j=0;j<SND_BUFLEN;j++) {
+                        buf_out[2*j+i] = scale*sinf(phase_out[i]*2.0f*(float)M_PI/(float)UINT32_MAX);
+                        phase_out[i] += ftw[i];  // wraps on overflow
+                    }
                 buf_out_idx = 0;
             }
             size_t written = sio_write(hdl, &buf_out[buf_out_idx], sizeof(buf_out) - buf_out_idx*sizeof(buf_out[0]));
@@ -82,7 +85,7 @@ static void dsp_thread()
         }
 
         if(revents & POLLIN) {
-            int16_t buf_in[SND_BUFLEN*SND_RCHAN];
+            int16_t buf_in[SND_BUFLEN];
             sio_read(hdl, buf_in, sizeof(buf_in));
             for(int i=0;i<10;i++)
               std::cout << buf_in[i] << " ";
@@ -135,6 +138,9 @@ int main(int argc, char* argv[])
     ImGui_ImplOpenGL3_Init("#version 130");
     std::atexit(ImGui_ImplOpenGL3_Shutdown);
 
+    for(int i=0;i<SND_PCHAN;i++)
+        frequency[i] = 441.0 + 202.0*i;
+
     static std::thread dsp_thread_h = std::thread(dsp_thread);
     static auto JoinDSP = []() {
         dsp_thread_h.join();
@@ -162,9 +168,15 @@ int main(int argc, char* argv[])
         ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
         ImGui::Begin("sndlock", nullptr, ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_NoResize);
 
-        float frequency_l = frequency;
-        ImGui::SliderFloat("Frequency", &frequency_l, 50.0f, 8000.0f);
-        frequency = frequency_l;
+        if(ImGui::CollapsingHeader("Modulation", ImGuiTreeNodeFlags_DefaultOpen)) {
+            for(int i=0;i<SND_PCHAN;i++) {
+                char str[64];
+                sprintf(str, "Frequency ch%d", i);
+                float frequency_l = frequency[i];
+                ImGui::SliderFloat(str, &frequency_l, 50.0f, 8000.0f);
+                frequency[i] = frequency_l;
+            }
+        }
         if(ImGui::Button("Exit"))
             exit = true;