atari2600/source/speaker.cpp

#include "speaker.h"
#include <SDL3/SDL.h>
#include <vector>
#include <stdlib.h>

namespace speaker
{
    int sampling_freq = 44100;
    uint16_t audio_buffer_size = 1024;
    SDL_AudioStream* sdlAudioStream = nullptr;
    uint8_t *sound_buffer = nullptr;
    uint16_t sound_pos=0;
    float t_sound=0.0f;
    float cycles_per_sample = 0.0f;

    std::vector<uint8_t(*)()> sources;

    void init(float clock_frequency)
    {
        if (sound_buffer) quit();

        SDL_AudioSpec audioSpec{SDL_AUDIO_U8, 1, sampling_freq};

        sdlAudioStream = SDL_OpenAudioDeviceStream(SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK, &audioSpec, nullptr, nullptr);

        cycles_per_sample = clock_frequency / (float)sampling_freq;
        sound_buffer = (uint8_t*)malloc(audio_buffer_size);
        sound_pos = 0;
        t_sound = 0.0f;
        
        enable();
    }

    void quit()
    {
        disable();
        sources.clear();
        if (sound_buffer) {
            free(sound_buffer);
            sound_buffer = nullptr;
        }
        if (sdlAudioStream) {
            SDL_DestroyAudioStream(sdlAudioStream);
            sdlAudioStream = nullptr;
        }
    }

    void enable()
    {
        SDL_ResumeAudioStreamDevice(sdlAudioStream);
    }

    void disable()
    {
        SDL_PauseAudioStreamDevice(sdlAudioStream);
    }

    void register_source(uint8_t(*callback)())
    {
        sources.push_back(callback);
    }

    void update(const uint32_t dt)
    {
        t_sound += (float)dt;
        if (t_sound >= cycles_per_sample)
        {
            t_sound -= cycles_per_sample;

            uint32_t sample = 0;
            for (auto callback : sources) sample += callback();
            sample /= sources.size();
            
            sound_buffer[sound_pos++] = (uint8_t)sample;
        }

        if (sound_pos >= audio_buffer_size)
        {
            SDL_PutAudioStreamData(sdlAudioStream, sound_buffer, sound_pos);
            sound_pos = 0;
            
            while (SDL_GetAudioStreamQueued(sdlAudioStream) > 2048)
            { 
                SDL_Delay(1); 
            }
        }
    }
}