rtaudio hello world

CMakeLists.txt

@@ -5,6 +5,33 @@ project(sonobulus LANGUAGES CXX)
 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
+# get dependencies
+include(FetchContent)
+set(RTAUDIO_BUILD_TESTING OFF CACHE BOOL "" FORCE)
+set(RTMIDI_BUILD_TESTING OFF CACHE BOOL "" FORCE)
+set(BUILD_TESTING OFF CACHE BOOL "" FORCE)
+set(RTAUDIO_TARGETNAME_UNINSTALL rtaudio-uninstall CACHE STRING "" FORCE)
+set(RTMIDI_TARGETNAME_UNINSTALL rtmidi-uninstall CACHE STRING "" FORCE)
+FetchContent_Declare(
+    rtaudio
+    GIT_REPOSITORY  https://github.com/thestk/rtaudio.git
+    GIT_TAG         6.0.1
+)
+FetchContent_Declare(
+    rtmidi
+    GIT_REPOSITORY  https://github.com/thestk/rtmidi.git
+    GIT_TAG         6.0.0
+)
+# FetchContent_Declare(
+#     libconfig
+#     GIT_REPOSITORY  https://github.com/hyperrealm/libconfig.git
+#     GIT_TAG         v1.8.2
+# )
+FetchContent_MakeAvailable(rtaudio)
+FetchContent_MakeAvailable(rtmidi)
+# FetchContent_MakeAvailable(libconfig)
+
+# needs to be preinstalled
 find_package(Qt6 REQUIRED COMPONENTS
     Core
     Quick  
@@ -13,11 +40,20 @@ find_package(Qt6 REQUIRED COMPONENTS
 qt_standard_project_setup()
 
 add_library(sonobulus_core STATIC
+    src/synth/AudioEngine.cpp
     src/TimerComponent.cpp
 )
 target_link_libraries(sonobulus_core PRIVATE
     Qt6::Core
     Qt6::Quick
+    rtaudio
+    rtmidi
+)
+
+message(STATUS "Looking for compiler dependencies: ${rtaudio_SOURCE_DIR}...")
+
+target_include_directories(sonobulus_core PRIVATE 
+    ${rtaudio_SOURCE_DIR}
 )
 
 qt_add_executable(sonobulus
@@ -30,6 +66,10 @@ qt_add_qml_module(sonobulus
     QML_FILES ui/Main.qml
 )
 
+target_include_directories(sonobulus PRIVATE 
+    ${rtaudio_SOURCE_DIR}
+)
+
 target_link_libraries(sonobulus PRIVATE
     sonobulus_core
     Qt6::Core
@@ -45,6 +85,12 @@ if (WIN32)
         COMMENT "windeployqt..."
         VERBATIM
     )
+    add_custom_command(
+        TARGET sonobulus POST_BUILD
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different
+        $<TARGET_FILE:rtaudio>
+        $<TARGET_FILE_DIR:sonobulus>
+    )
 endif()
 
 # add_subdirectory(src)

README.md

@@ -19,9 +19,9 @@ requirements (hundreds or even thousands of calculations for a single sample at
 to produce somewhat well-sounding instruments and music performance.
 
 ## Development plan: 
-- [ ] Build & project setup, get working hello-world program.
+- [x] Build & project setup, get working hello-world program.
-- [ ] QML hello-world program: basic increment/reset counter
+- [x] QML hello-world program: basic increment/reset counter
-- [ ] RtAudio hello-world: basic sine output
+- [x] RtAudio hello-world: basic sine output
 - [ ] Connect UI control to sound output, add a slider for frequency control
 - [ ] Add note control a keyboard. Coordinate on-off events to
       start and stop tone generation

src/main.cpp

@@ -6,6 +6,7 @@
 #include <QQmlContext>
 
 #include "TimerComponent.hpp"
+#include "synth/AudioEngine.hpp"
 
 int main(int argc, char* argv[]) {
 
@@ -27,6 +28,10 @@ int main(int argc, char* argv[]) {
         return -1;
     }
 
+    // audio synthesizer doohickey
+    AudioEngine audioEngine = AudioEngine();
+    audioEngine.start();
+
     // execute app
     return app.exec();
 }

src/synth/AudioEngine.cpp

@@ -1,2 +1,85 @@
 
 #include "AudioEngine.hpp"
+
+#include <iostream>
+#include <cmath>
+#include <numbers>
+
+AudioEngine::AudioEngine() {
+
+    if(audioDevice_.getDeviceCount() < 1) {
+        std::cout << "No audio devices found" << std::endl;
+    }
+
+}
+
+AudioEngine::~AudioEngine() {
+    (void)stop();
+}
+
+bool AudioEngine::start() {
+
+    // initialize the audio engine
+    RtAudio::StreamParameters params;
+    params.deviceId = audioDevice_.getDefaultOutputDevice();
+    params.nChannels = channels_; // we're doing two duplicate channels for pseudo-mono
+    params.firstChannel = 0;
+
+    RtAudio::StreamOptions options;
+    options.flags = RTAUDIO_MINIMIZE_LATENCY;
+
+    RtAudioErrorType status = audioDevice_.openStream(&params, nullptr, RTAUDIO_FLOAT32, sampleRate_, &bufferFrames_, &AudioEngine::audioCallback, this, &options);
+    if(status != RTAUDIO_NO_ERROR) {
+        std::cout << "Error opening RtAudio stream" << std::endl;
+        return false;
+    } 
+    
+    status = audioDevice_.startStream();
+    if(status != RTAUDIO_NO_ERROR) {
+        std::cout << "Error starting RtAudio stream" << std::endl;
+        return false;
+    } 
+
+    // sanity check
+    std::cout << "sample rate: " << sampleRate_ << "  buffer frames: " << bufferFrames_ << std::endl;
+    return true;
+
+}
+
+bool AudioEngine::stop() {
+
+    if(audioDevice_.isStreamRunning()) audioDevice_.stopStream();
+    if(audioDevice_.isStreamOpen()) audioDevice_.closeStream();
+
+    return true;
+
+}
+
+int32_t AudioEngine::audioCallback(void* outputBuffer, void* inputBuffer, uint32_t nFrames, double, RtAudioStreamStatus status, void* userData) {
+
+    // error if the callback is late
+    if(status) std::cout << "stream underflow" << std::endl;
+
+    return static_cast<AudioEngine*>(userData)->process(static_cast<float*>(outputBuffer), static_cast<size_t>(nFrames));
+
+}
+
+int32_t AudioEngine::process(float* out, size_t nFrames) {
+
+    for(size_t i = 0; i < nFrames; i++) {
+
+        // simulate a sine wave
+        phase_ += 0.04f;
+        const float twoPi = 2.0f*std::numbers::pi_v<float>;
+        if(phase_ > twoPi) {
+            phase_ -= twoPi;
+        }
+        float outSample = std::sin(phase_) / 4.0f;
+
+        out[2*i] = outSample;
+        out[2*i+1] = outSample;
+    }
+
+    return 0;
+
+}

src/synth/AudioEngine.hpp

@@ -1,2 +1,39 @@
 
 // The audio engine handles the RtAudio implementation of outputing samples to audio. the audio callback fills a buffer of audio samples and submits it for playback
+
+#pragma once
+
+#include <RtAudio.h>
+
+#if defined(_WIN32)
+    #define AUDIO_API RtAudio::WINDOWS_WASAPI
+#else
+    #define AUDIO_API RtAudio::LINUX_ALSA
+#endif
+
+class AudioEngine {
+
+public:
+
+    AudioEngine();
+    ~AudioEngine();
+
+    bool start();
+    bool stop();
+
+private:
+
+    static int32_t audioCallback(void* outputBuffer, void* inputBuffer, uint32_t nFrames, double streamtime, RtAudioStreamStatus status, void* userData);
+
+    int32_t process(float* out, size_t nFrames);
+
+    RtAudio audioDevice_ { AUDIO_API };
+
+    // TODO: make these configurable
+    uint32_t sampleRate_ = 44100;
+    uint32_t bufferFrames_ = 512;
+    uint32_t channels_ = 2;
+
+    float phase_ = 0.0f;
+
+};