looper/playback.cpp

#include "playback.h"
#include "SDL_mixer.h"
#include <SDL_audio.h>
#include <SDL.h>
#include <exception>
#include <thread>
using namespace std::chrono;
size_t CalculateBufSize(SDL_AudioSpec *obtained, double max_seconds, size_t samples_override = 0) {
    return ((((samples_override == 0) ? obtained->samples : samples_override) * max_seconds) + 1) * sizeof(SAMPLETYPE) * obtained->channels;
}
void Playback::SDLCallbackInner(Uint8 *stream, int len) {
    while (st->numSamples() < len) {
        general_mixer(NULL, buf, bufsize);
        st->putSamples((SAMPLETYPE*)buf, bufsize / sizeof(SAMPLETYPE) / spec.channels);
    }
    SDL_memset((void*)stream, 0, len);
    st->receiveSamples((SAMPLETYPE*)stream, len / sizeof(SAMPLETYPE) / spec.channels);
}
void Playback::SDLCallback(void *userdata, Uint8 *stream, int len) {
    ((Playback*)userdata)->SDLCallbackInner(stream, len);
}
Mix_Music *Playback::Load(const char *file) {
    Mix_Music *output = Mix_LoadMUS(file);
    if (!output) {
        printf("Error loading music '%s': %s\n", file, Mix_GetError());
        throw std::exception();
    }
    Mix_PlayMusicStream(output, -1);
    length = Mix_MusicDuration(output);
    update.store(true);
    return output;
}
void Playback::Unload(Mix_Music *music) {
    Mix_HaltMusicStream(music);
    Mix_FreeMusic(music);
}
void Playback::ThreadFunc() {
    if (!SDL_WasInit(SDL_INIT_AUDIO)) {
        if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) {
            printf("Error initializing SDL: '%s'\n", SDL_GetError());
            throw std::exception();
        }
    }
    SDL_AudioSpec obtained;
    SDL_AudioSpec desired;
    desired.format = 
    #ifdef SOUNDTOUCH_INTEGER_SAMPLES
        AUDIO_S16SYS;
    #else
        AUDIO_F32SYS;
    #endif
    desired.freq = 48000;
    desired.samples = 128;
    desired.channels = 2;
    desired.callback = Playback::SDLCallback;
    desired.userdata = this;
    st = new SoundTouch();
    st->setSampleRate(desired.freq);
    st->setChannels(desired.channels);
    Mix_Init(MIX_INIT_FLAC|MIX_INIT_MID|MIX_INIT_MOD|MIX_INIT_MP3|MIX_INIT_OGG|MIX_INIT_OPUS|MIX_INIT_WAVPACK);
    if ((device = SDL_OpenAudioDevice(NULL, 0, &desired, &obtained, 0)) == 0) {
        printf("Error opening audio device: '%s'\n", SDL_GetError());
        throw std::exception();
    }
    spec = obtained;
    bufsize = spec.size;
    buf = (Uint8*)malloc(bufsize);
    general_mixer = Mix_GetGeneralMixer();
    Mix_InitMixer(&spec, SDL_TRUE);
    SDL_PauseAudioDevice(device, 0);
    Mix_Music *music = Load(filePath.c_str());

    while (running) {
        if (file_changed.exchange(false)) {
            Unload(music);
            music = Load(filePath.c_str());
        }
        if (flag_mutex.try_lock()) {
            if (seeking.exchange(false)) {
                Mix_SetMusicPositionStream(music, position);
            }
            if (paused) {
                Mix_PauseMusicStream(music);
            } else {
                Mix_ResumeMusicStream(music);
            }
            if (update.exchange(false)) {
                Mix_VolumeMusicStream(music, (volume / 100.0 * MIX_MAX_VOLUME));
                SDL_LockAudioDevice(device);
                if (speed > 0.0f) {
                    st->setRate(speed);
                }
                if (tempo > 0.0f) {
                    st->setTempo(tempo);
                }
                if (pitch > 0.0f) {
                    st->setPitch(pitch);
                }
                SDL_UnlockAudioDevice(device);
            }
            flag_mutex.unlock();
        }
        position = Mix_GetMusicPosition(music);
        std::this_thread::sleep_for(20ms);
    }
    // ====
    Unload(music);
    Mix_CloseAudio();
    Mix_Quit();
    SDL_CloseAudioDevice(device);
    delete st;
    free(buf);
}

Playback::Playback() {
    running = false;
    paused = true;
    position = 0;
    length = 0;
    volume = 100.0;
    speed = 1.0;
    pitch = 1.0;
    tempo = 1.0;
}

Playback::~Playback() {
    Stop();
}

void Playback::Start(std::string filePath) {
    this->filePath = filePath;
    printf("Playing %s...\n", filePath.c_str());
    flag_mutex.lock();
    paused = false;
    Update();
    if (running.exchange(true)) {
        file_changed.store(true);
    } else {
        thread = std::thread(&Playback::ThreadFunc, this);
    }
    flag_mutex.unlock();
}
double Playback::GetPosition() {
    return position;
}
double Playback::GetLength() {
    return length;
}

void Playback::Seek(double position) {
    flag_mutex.lock();
    this->position = position;
    seeking.store(true);
    flag_mutex.unlock();
}

void Playback::Pause() {
    flag_mutex.lock();
    paused = !paused;
    flag_mutex.unlock();
}

bool Playback::IsPaused() {
    return paused;
}

void Playback::Stop() {
    if (running.exchange(false)) {
        thread.join();
    }
}

void Playback::Update() {
    update.store(true);
}

bool Playback::IsStopped() {
    return !running;
}