89 lines
3.1 KiB
C++
89 lines
3.1 KiB
C++
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#include "ultra64.h"
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#include "multilibultra.hpp"
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#include "SDL.h"
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#include "SDL_audio.h"
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#include <cassert>
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static SDL_AudioDeviceID audio_device = 0;
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static uint32_t sample_rate = 48000;
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void Multilibultra::init_audio() {
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// Initialize SDL audio.
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SDL_InitSubSystem(SDL_INIT_AUDIO);
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// Pick an initial dummy sample rate; this will be set by the game later to the true sample rate.
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set_audio_frequency(48000);
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}
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void Multilibultra::set_audio_frequency(uint32_t freq) {
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if (audio_device != 0) {
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SDL_CloseAudioDevice(audio_device);
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}
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SDL_AudioSpec spec_desired{
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.freq = (int)freq,
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.format = AUDIO_S16,
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.channels = 2,
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.silence = 0, // calculated
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.samples = 0x100, // Fairly small sample count to reduce the latency of internal buffering
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.padding = 0, // unused
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.size = 0, // calculated
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.callback = nullptr,//feed_audio, // Use a callback as QueueAudio causes popping
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.userdata = nullptr
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};
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audio_device = SDL_OpenAudioDevice(nullptr, false, &spec_desired, nullptr, 0);
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if (audio_device == 0) {
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printf("SDL Error: %s\n", SDL_GetError());
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fflush(stdout);
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assert(false);
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}
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SDL_PauseAudioDevice(audio_device, 0);
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sample_rate = freq;
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}
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void Multilibultra::queue_audio_buffer(RDRAM_ARG PTR(s16) audio_data_, uint32_t byte_count) {
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// Buffer for holding the output of swapping the audio channels. This is reused across
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// calls to reduce runtime allocations.
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static std::vector<uint16_t> swap_buffer;
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// Ensure that the byte count is an integer multiple of samples.
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assert((byte_count & 1) == 0);
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// Calculate the number of samples from the number of bytes.
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uint32_t sample_count = byte_count / sizeof(s16);
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// Make sure the swap buffer is large enough to hold all the incoming audio data.
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if (sample_count > swap_buffer.size()) {
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swap_buffer.resize(sample_count);
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}
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// Swap the audio channels into the swap buffer to correct for the address xor caused by endianness handling.
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s16* audio_data = TO_PTR(s16, audio_data_);
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for (size_t i = 0; i < sample_count; i += 2) {
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swap_buffer[i + 0] = audio_data[i + 1];
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swap_buffer[i + 1] = audio_data[i + 0];
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}
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// Queue the swapped audio data.
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SDL_QueueAudio(audio_device, swap_buffer.data(), byte_count);
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}
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// If there's ever any audio popping, check here first. Some games are very sensitive to
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// the remaining sample count and reporting a number that's too high here can lead to issues.
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// Reporting a number that's too low can lead to audio lag in some games.
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uint32_t Multilibultra::get_remaining_audio_bytes() {
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// Get the number of remaining buffered audio bytes.
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uint32_t buffered_byte_count = SDL_GetQueuedAudioSize(audio_device);
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// Adjust the reported count to be four refreshes in the future, which helps ensure that
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// there are enough samples even if the game experiences a small amount of lag. This prevents
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// audio popping on games that use the buffered audio byte count to determine how many samples
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// to generate.
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uint32_t samples_per_vi = (sample_rate / 60);
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if (buffered_byte_count > (4u * samples_per_vi)) {
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buffered_byte_count -= (4u * samples_per_vi);
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} else {
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buffered_byte_count = 0;
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}
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return buffered_byte_count;
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}
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