looper/playback.cpp

#include "playback.h"
#include "SDL_mixer.h"
#include <SDL_audio.h>
#include <SDL.h>
#include <exception>
#include <thread>
#include <cmath>
#ifdef __linux__
#include <pthread.h>
#endif
using namespace std::chrono;
size_t CalculateBufSize(SDL_AudioSpec *obtained, double seconds, double max_seconds, size_t samples_override = 0) {
    return ((((samples_override == 0) ? obtained->samples : samples_override) * std::min(seconds, max_seconds)) + 1) * sizeof(SAMPLETYPE) * obtained->channels;
}
void Playback::SDLCallbackInner(Uint8 *stream, int len) {
    SDL_memset((void*)stream, 0, len);
    if (!playback_ready.load()) {
        return;
    }
    size_t i = 0;
    size_t max = 0;
    size_t unit = sizeof(SAMPLETYPE) * spec.channels;
    size_t bytes_per_iter = std::min(((bufsize / unit)) * unit, (size_t)fakespec.size);
    while (st->numSamples() <= (uint)len) {
        if (general_mixer == nullptr) {
            return;
        }
        general_mixer(NULL, buf + i, bytes_per_iter);
        i += bytes_per_iter;
        max = i + bytes_per_iter;
        if (i + bytes_per_iter >= bufsize) {
            st->putSamples((SAMPLETYPE*)buf, i / unit);
            max = 0;
            i = 0;
            SDL_memset((void*)buf, 0, bufsize);
        }
    }
    st->putSamples((SAMPLETYPE*)buf, max / unit);
    st->receiveSamples((SAMPLETYPE*)stream, len / unit);
}
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::UpdateST() {
    if (speed > 0.0f) {
        st->setRate(speed);
    }
    if (tempo > 0.0f) {
        st->setTempo(tempo);
    }
    if (pitch > 0.0f) {
        st->setPitch(pitch);
    }
}
double Playback::GetMaxSeconds() {
    return std::max(MaxSpeed * MaxTempo, st->getInputOutputSampleRatio());
}
void Playback::ThreadFunc() {
    #ifdef __linux__
    pthread_setname_np(pthread_self(), "Playback control thread");
    #endif
    bool reload = false;
    while (running) {
        playback_ready.store(false);
        if (reload) {
            printf("Resuming playback...\n");
        }
        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 = 1024;
        desired.channels = 2;
        desired.callback = Playback::SDLCallback;
        desired.userdata = this;
        st = new SoundTouch();
        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, SDL_AUDIO_ALLOW_CHANNELS_CHANGE|SDL_AUDIO_ALLOW_FREQUENCY_CHANGE|SDL_AUDIO_ALLOW_SAMPLES_CHANGE)) == 0) {
            printf("Error opening audio device: '%s'\n", SDL_GetError());
            throw std::exception();
        }
        spec = obtained;
        st->setSampleRate(spec.freq);
        st->setChannels(spec.channels);
        UpdateST();
        bufsize = 0;
        fakespec = spec;
        double maxSeconds = GetMaxSeconds();
        fakespec.size *= maxSeconds;
        fakespec.samples *= maxSeconds;
        size_t new_bufsize = CalculateBufSize(&spec, GetMaxSeconds(), MaxSeconds);
        buf = (Uint8*)malloc(new_bufsize);
        if (buf == NULL) {
            throw std::exception();
        }
        bufsize = new_bufsize;
        general_mixer = Mix_GetGeneralMixer();
        Mix_InitMixer(&fakespec, SDL_TRUE);
        SDL_PauseAudioDevice(device, 0);
        Mix_Music *music = Load(filePath.c_str());
        if (reload) {
            Seek(position);
        }
        reload = false;
        playback_ready.store(true);
        while (running && !reload) {
            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);
                    UpdateST();
                    size_t correct_buf_size = CalculateBufSize(&spec, GetMaxSeconds(), MaxSeconds);
                    size_t max_buf_size = correct_buf_size * 10;
                    bool too_large = max_buf_size < bufsize;
                    bool too_small = correct_buf_size > bufsize;
                    if (too_large) {
                        printf("Bufsize is too large - ");
                    } else if (too_small) {
                        printf("Bufsize is too small - ");
                    }
                    if (too_large || too_small) {
                        printf("Resizing buffer...\n");
                        general_mixer = nullptr;
                        bufsize = 0;
                        buf = (Uint8*)realloc((void*)buf, correct_buf_size);
                        if (buf == NULL) {
                            break;
                        }
                        bufsize = correct_buf_size;
                    }
                    SDL_UnlockAudioDevice(device);
                }
                flag_mutex.unlock();
            }
            position = Mix_GetMusicPosition(music);
            std::this_thread::sleep_for(20ms);
        }
        playback_ready.store(false);
        // ====
        Unload(music);
        SDL_CloseAudioDevice(device);
        Mix_CloseAudio();
        Mix_Quit();
        SDL_QuitSubSystem(SDL_INIT_AUDIO);
        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();
    this->position = 0.0;
    seeking.store(true);
    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;
}