(20111213)

Audio.c

@@ -0,0 +1,259 @@
+#ifdef WIN32
+	#define _WIN32_WINNT 0x0501
+	#include <windows.h>
+#endif
+#include <SDL/SDL.h>
+
+#include "Audio.h"
+
+static void Audio_MixerCallback(void *ud,Uint8 *stream,int l);
+
+
+////////////////////////////////////////////////
+// AudioWave //
+///////////////
+// Reference to a sound.
+typedef struct Tag_AudioWave {
+	SDL_AudioSpec spec;
+	Uint32 len;
+	Uint8 *buffer;
+
+	struct Tag_AudioWave *next;
+} AudioWave;
+AudioWave *_waves=NULL;
+
+
+////////////////////////////////////////////////
+// AudioChan //
+///////////////
+// Reference to a sound.
+typedef struct Tag_AudioChan {
+	AudioWave *wave;
+	Uint32 pos;
+	unsigned char rightvol;
+	unsigned char leftvol;
+
+	struct Tag_AudioChan *next;
+} AudioChan;
+AudioChan *_channels=NULL;
+AudioChan *_free_channels=NULL;
+
+/////////////////////////////
+// Audio_Init
+//
+// Initializes the game audio.
+int Audio_Init(){
+	SDL_AudioSpec as;
+	SDL_AudioSpec as2;
+
+	// Initialize audio subsistem
+#ifdef WIN32
+	// Force DSound Driver on win32
+	putenv("SDL_AUDIODRIVER=dsound");
+#endif
+	if(SDL_InitSubSystem(SDL_INIT_AUDIO) < 0){
+		printf("Audio_Init: Failure initializing SDL Audio.\n");
+		printf("Audio_Init: SDL Error: %s\n",SDL_GetError());
+		return(0);
+	}
+
+	// Open the audio device using the desired parameters
+	as.freq = 44100;
+	as.format = AUDIO_S16SYS;
+	as.channels = 2;
+	as.samples = 1024;
+	as.callback = Audio_MixerCallback;
+	if(SDL_OpenAudio(&as, &as2) < 0){
+		printf("Audio_Init: Failure opening audio.\n");
+		printf("Audio_Init: SDL Error: %s\n",SDL_GetError());
+		return(0);
+	}
+
+	// Asert results
+	if(	as2.format   != AUDIO_S16SYS ||
+		as2.freq     != 44100 ||
+		as2.channels != 2 )
+	{
+		printf("Audio_Init: Failure opening audio. (44.1Khz/16b/2c).\n");
+		SDL_CloseAudio();
+		return(0);
+	}
+
+	// Unpause and ready to go
+	SDL_PauseAudio(0);
+
+	return(1);
+}
+
+
+/////////////////////////////
+// Audio_MixerCallback
+//
+// Mixes the audio channels.
+static void Audio_MixerCallback(void *ud,Uint8 *stream,int l){
+	signed short *ptr_out,*ptr_wave;
+	AudioChan *prevchan;
+	AudioChan *chan;
+	AudioWave *wave;
+	int len=l/4; // Asume 16bpb and 2 output chan
+	int chan_remain;
+	int len_mix;
+	int i;
+
+	// Clean
+	memset(stream,0,len);
+
+	// Mix all the channels
+	prevchan=NULL;
+	chan=_channels;
+	while(chan){
+		if(!chan->wave){
+			// Remove finished channels
+			AudioChan *aux_chan=chan->next;
+			chan->next=_free_channels;
+			_free_channels=chan;
+			chan=aux_chan;
+			if(prevchan){
+				prevchan->next=chan;
+			}else{
+				_channels=chan;
+			}
+			continue;
+		}
+
+		// Prepare the pointers
+		ptr_out=(signed short *)stream;
+		ptr_wave=((signed short *)chan->wave->buffer)+chan->pos;
+		wave=chan->wave;
+
+		// Determine mixing lenght
+		chan_remain=wave->len-chan->pos;
+		if(chan_remain>len){
+			len_mix=len;
+		}else{
+			len_mix=chan_remain;
+			chan->wave=NULL;
+		}
+
+		// Mix the buffer
+		for(i=0;i<len_mix;i++){
+			int temp;
+
+			// Left Channel
+			temp=ptr_out[0];
+			temp+=(ptr_wave[0]*chan->leftvol)>>8;
+			if(temp>(1<<14)){
+				ptr_out[0]=1<<14;
+			}else if(temp<-(1<<14)){
+				ptr_out[0]=-(1<<14);
+			}else{
+				ptr_out[0]=temp;
+			}
+
+			// Right Channel
+			temp=ptr_out[1];
+			temp+=(ptr_wave[0]*chan->rightvol)>>8;
+			if(temp>(1<<14)){
+				ptr_out[1]=1<<14;
+			}else if(temp<-(1<<14)){
+				ptr_out[1]=-(1<<14);
+			}else{
+				ptr_out[1]=temp;
+			}
+
+			// Next sample
+			ptr_out+=2;
+			ptr_wave++;
+		}
+		chan->pos+=len_mix;
+
+		// Next channel
+		prevchan=chan;
+		chan=chan->next;
+	}
+}
+
+
+/////////////////////////////
+// Audio_Frame
+//
+// Notify a frame update to the audio subsystem.
+void Audio_Frame(){
+
+}
+
+
+/////////////////////////////
+// Audio_LoadSound
+//
+// Loads a sound, giving a reference.
+AudioSnd Audio_LoadSound(char *filename){
+	AudioWave *wave;
+
+	// Allocate and load the sound
+	wave=malloc(sizeof(AudioWave));
+	if( SDL_LoadWAV(filename,
+		&wave->spec, &wave->buffer, &wave->len) == NULL )
+	{
+		printf("Audio_LoadSound: Failure Loading sound: %s\n",filename);
+		printf("Audio_LoadSound: SDL Error: %s\n",SDL_GetError());
+		free(wave);
+		return(NULL);
+	}
+
+	// Asert results
+	if(	wave->spec.format   != AUDIO_S16 ||
+		wave->spec.freq     != 44100 ||
+		wave->spec.channels != 1 )
+	{
+		printf("Audio_LoadSound: Failure opening sound. (44.1Khz/16b/1c).\n");
+		SDL_FreeWAV(wave->buffer);
+		free(wave);
+		return(0);
+	}
+
+	// Correct the lenght
+	wave->len/=2;
+
+	// Take a reference
+	wave->next=_waves;
+	_waves=wave;
+
+	return((AudioSnd)wave);
+}
+
+
+/////////////////////////////
+// Audio_PlaySound
+//
+// Loads a sound, giving a reference.
+void Audio_PlaySound(AudioSnd snd,
+	float leftvol, float rightvol)
+{
+	AudioChan *chan;
+	AudioWave *wave;
+	if(!snd)
+		return;
+
+	// Cast AudioSnd to AudioWave
+	wave=snd;
+
+	// Get a free channel
+	if(_free_channels){
+		chan=_free_channels;
+		_free_channels=chan->next;
+		chan->next=NULL;
+	}else{
+		chan=malloc(sizeof(AudioChan));
+		chan->next=NULL;
+	}
+
+	// Initialize the channel
+	chan->wave=wave;
+	chan->pos=0;
+	chan->rightvol=(rightvol*255);
+	chan->leftvol=(leftvol*255);
+	chan->next=_channels;
+	_channels=chan;
+}
+