124 lines
2.8 KiB
C++
124 lines
2.8 KiB
C++
// Released under the MIT licence.
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// See LICENCE.txt for details.
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#include "Backend.h"
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#include <stddef.h>
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#include <string.h>
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#include <string>
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#include "SDL.h"
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#include "../../Misc.h"
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#define MIN(a, b) ((a) < (b) ? (a) : (b))
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static void (*parent_callback)(long *stream, size_t frames_total);
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static SDL_AudioDeviceID device_id;
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static void Callback(void *user_data, Uint8 *stream_uint8, int len)
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{
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(void)user_data;
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short *stream = (short*)stream_uint8;
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const size_t frames_total = len / sizeof(short) / 2;
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size_t frames_done = 0;
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while (frames_done != frames_total)
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{
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long mix_buffer[0x800 * 2]; // 2 because stereo
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size_t subframes = MIN(0x800, frames_total - frames_done);
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memset(mix_buffer, 0, subframes * sizeof(long) * 2);
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parent_callback(mix_buffer, subframes);
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for (size_t i = 0; i < subframes * 2; ++i)
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{
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if (mix_buffer[i] > 0x7FFF)
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*stream++ = 0x7FFF;
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else if (mix_buffer[i] < -0x7FFF)
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*stream++ = -0x7FFF;
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else
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*stream++ = mix_buffer[i];
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}
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frames_done += subframes;
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}
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}
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unsigned long SoftwareMixerBackend_Init(void (*callback)(long *stream, size_t frames_total))
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{
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if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0)
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{
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std::string errorMessage = std::string("'SDL_InitSubSystem(SDL_INIT_AUDIO)' failed: ") + SDL_GetError();
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Backend_ShowMessageBox("Fatal error (SDL2 audio backend)", errorMessage.c_str());
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return 0;
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}
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Backend_PrintInfo("Available SDL audio drivers:");
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for (int i = 0; i < SDL_GetNumAudioDrivers(); ++i)
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Backend_PrintInfo("%s", SDL_GetAudioDriver(i));
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SDL_AudioSpec specification;
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specification.freq = 48000;
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specification.format = AUDIO_S16;
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specification.channels = 2;
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specification.samples = 0x400; // Roughly 10 milliseconds for 48000Hz
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specification.callback = Callback;
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specification.userdata = NULL;
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SDL_AudioSpec obtained_specification;
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device_id = SDL_OpenAudioDevice(NULL, 0, &specification, &obtained_specification, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE);
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if (device_id == 0)
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{
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std::string error_message = std::string("'SDL_OpenAudioDevice' failed: ") + SDL_GetError();
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Backend_ShowMessageBox("Fatal error (SDL2 audio backend)", error_message.c_str());
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return 0;
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}
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Backend_PrintInfo("Selected SDL audio driver: %s", SDL_GetCurrentAudioDriver());
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parent_callback = callback;
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return obtained_specification.freq;
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}
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void SoftwareMixerBackend_Deinit(void)
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{
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SDL_CloseAudioDevice(device_id);
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SDL_QuitSubSystem(SDL_INIT_AUDIO);
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}
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bool SoftwareMixerBackend_Start(void)
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{
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SDL_PauseAudioDevice(device_id, 0);
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return true;
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}
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void SoftwareMixerBackend_LockMixerMutex(void)
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{
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SDL_LockAudioDevice(device_id);
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}
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void SoftwareMixerBackend_UnlockMixerMutex(void)
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{
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SDL_UnlockAudioDevice(device_id);
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}
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void SoftwareMixerBackend_LockOrganyaMutex(void)
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{
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SDL_LockAudioDevice(device_id);
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}
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void SoftwareMixerBackend_UnlockOrganyaMutex(void)
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{
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SDL_UnlockAudioDevice(device_id);
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}
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