SDL_!OpenAudio?
NAME SYNOPSIS DESCRIPTION EXAMPLES SEE ALSO
SDL_!OpenAudio?- Opens the audio device with the desired parameters.
#include
int SDL_!OpenAudio?(SDL_!AudioSpec? *desired, SDL_!AudioSpec? *obtained);
This function opens the audio device with the desired parameters, and returns 0 if successful, placing the actual hardware parameters in the structure pointed to by obtained. If obtained is NULL, the audio data passed to the callback function will be guaranteed to be in the requested format, and will be automatically converted to the hardware audio format if necessary. This function returns -1 if it failed to open the audio device, or couldn't set up the audio thread.
To open the audio device a desired SDL_!AudioSpec? must be created.
SDL_!AudioSpec? *desired; . . desired=(SDL_!AudioSpec? *)malloc(sizeof(SDL_!AudioSpec?)); You must then fill this structure with your desired audio specifications.
desired-freq
desired-format
desired-samples
desired-callback
void callback(void *userdata, Uint8 *stream, int len); userdata is the pointer stored in userdata field of the SDL_!AudioSpec?. stream is a pointer to the audio buffer you want to fill with information and len is the length of the audio buffer in bytes.
desired-userdata
SDL_!OpenAudio? reads these fields from the desired SDL_!AudioSpec? structure pass to the function and attempts to find an audio configuration matching your desired. As mentioned above, if the obtained parameter is NULL then SDL with convert from your desired audio settings to the hardware settings as it plays.
If obtained is NULL then the desired SDL_!AudioSpec? is your working specification, otherwise the obtained SDL_!AudioSpec? becomes the working specification and the desirec specification can be deleted. The data in the working specification is used when building SDL_AudioCVT's for converting loaded data to the hardware format.
SDL_!OpenAudio? calculates the size and silence fields for both the desired and obtained specifications. The size field stores the total size of the audio buffer in bytes, while the silence stores the value used to represent silence in the audio buffer
The audio device starts out playing silence when it's opened, and should be enabled for playing by calling SDL_!PauseAudio?(0) when you are ready for your audio callback function to be called. Since the audio driver may modify the requested size of the audio buffer, you should allocate any local mixing buffers after you open the audio device.
/* Prototype of our callback function / void my_audio_callback(void userdata, Uint8 stream, int len); / Open the audio device / SDL_!AudioSpec? *desired, *obtained; SDL_!AudioSpec? *hardware_spec; / Allocate a desired SDL_!AudioSpec? */ desired=(SDL_!AudioSpec? *)malloc(sizeof(SDL_!AudioSpec?)); / Allocate space for the obtained SDL_!AudioSpec? */ obtained=(SDL_!AudioSpec? *)malloc(sizeof(SDL_!AudioSpec?)); / 22050Hz - FM Radio quality */ desired-
SDL_!AudioSpec?, SDL_!LockAudio?, SDL_!UnlockAudio?, SDL_!PauseAudio?
One page links to SDL_OpenAudio(3):
