sdl-audio/audio.c

#include "audio.h"
#include "log.h"

#include <SDL2/SDL.h>

static SDL_AudioSpec recording_spec;
static SDL_AudioSpec playback_spec;
static SDL_AudioSpec received_recording_spec;
static SDL_AudioSpec received_playback_spec;

int audio_init(audio_state* state)
{
	state->recording_device_id = 0;
	state->playback_device_id = 0;

	SDL_zero(recording_spec);
	recording_spec.freq = 44100;
	recording_spec.format = AUDIO_S16;
	recording_spec.channels = 2;
	recording_spec.samples = 4096;
	recording_spec.callback = audio_recording_callback;
	recording_spec.userdata = state;

	SDL_zero(playback_spec);
	playback_spec.freq = 44100;
	playback_spec.format = AUDIO_S16;
	playback_spec.channels = 2;
	playback_spec.samples = 4096;
	playback_spec.callback = audio_playback_callback;
	playback_spec.userdata = state;

	state->recording_buffer = NULL;
	state->recording_buffer_size = 0;
	state->recording_buffer_position = 0;

	return 1;
}

int audio_recording_init(audio_state* state, int index)
{
	SDL_AudioDeviceID device_id = SDL_OpenAudioDevice(SDL_GetAudioDeviceName(index, 1), 1, &recording_spec, &received_recording_spec, SDL_AUDIO_ALLOW_FORMAT_CHANGE);
	log_message(LOG_INFO, "Recording Device: %s", SDL_GetAudioDeviceName(index, 1));
	if (!device_id) {
		log_message(LOG_INFO, "Failed to open recording device! SDL Error: %s", SDL_GetError());
		return 0;
	}
	state->recording_device_id = device_id;

	unsigned int bytes_per_sample = received_recording_spec.channels * (SDL_AUDIO_BITSIZE(received_recording_spec.format)/8);
	unsigned int bytes_per_second = received_recording_spec.freq * bytes_per_sample;
	state->recording_buffer_size = MAX_RECORDING_SECONDS * bytes_per_second;

	if (state->recording_buffer) free(state->recording_buffer);
	state->recording_buffer = malloc(state->recording_buffer_size);
	memset(state->recording_buffer, 0, state->recording_buffer_size);

	return 1;
}

void audio_destroy(audio_state* state)
{
	free(state->recording_buffer);
	SDL_CloseAudioDevice(state->recording_device_id);
	SDL_CloseAudioDevice(state->playback_device_id);
}

int audio_playback_init(audio_state* state)
{
	if (!state->recording_buffer) {
		log_message(LOG_INFO, "Audio buffer not initialized");
		return 0;
	}

	SDL_AudioDeviceID device_id = SDL_OpenAudioDevice(NULL, 0, &playback_spec, &received_playback_spec, SDL_AUDIO_ALLOW_FORMAT_CHANGE);
	if (!device_id) {
		log_message(LOG_INFO, "Failed to open playback device! SDL Error: %s", SDL_GetError());
		return 0;
	}
	state->playback_device_id = device_id;

	return 1;
}

void audio_recording_callback(void* userdata, uint8_t* stream, int len)
{
	audio_state* state = userdata;

	int space_left = state->recording_buffer_size - state->recording_buffer_position;
	if (space_left <= 0) {
		log_message(LOG_INFO, "Stopping recording ID: %i", state->recording_device_id);
		SDL_PauseAudioDevice(state->recording_device_id, 1);
		return;
	}

	if (len > space_left) {
		len = space_left;
	}

	memcpy(&state->recording_buffer[state->recording_buffer_position], stream, len);
	state->recording_buffer_position += len;

	log_message(LOG_INFO, "Record pos: %u/%u (%u)", state->recording_buffer_position, state->recording_buffer_size, len);
}

void audio_playback_callback(void* userdata, uint8_t* stream, int len)
{
	audio_state* state = userdata;

	int space_left = state->recording_buffer_size - state->recording_buffer_position;
	if (space_left <= 0) {
		log_message(LOG_INFO, "Stopping playback ID: %i", state->recording_device_id);
		SDL_PauseAudioDevice(state->playback_device_id, 1);
		return;
	}

	if (len > space_left) {
		len = space_left;
	}

	memcpy(stream, &state->recording_buffer[state->recording_buffer_position], len);
	state->recording_buffer_position += len;

	log_message(LOG_INFO, "Playback pos: %u/%u (%u)", state->recording_buffer_position, state->recording_buffer_size, len);
}