SDL_AudioSpec

Name

SDL_AudioSpec -- Audio Specification Structure

Structure Definition

typedef struct{
  int freq;
  Uint16 format;
  Uint8 channels;
  Uint8 silence;
  Uint16 samples;
  Uint32 size;
  void (*callback)(void *userdata, Uint8 *stream, int len);
  void *userdata;
} SDL_AudioSpec;

Structure Data

freq

Audio frequency in samples per second

format

Audio data format

channels

Number of channels: 1 mono, 2 stereo, 4 surround, 6 surround with center and lfe

silence

Audio buffer silence value (calculated)

samples

Audio buffer size in samples

size

Audio buffer size in bytes (calculated)

callback(..)

Callback function for filling the audio buffer

userdata

Pointer the user data which is passed to the callback function

Description

The SDL_AudioSpec structure is used to describe the format of some audio data. This structure is used by SDL_OpenAudio and SDL_LoadWAV. While all fields are used by SDL_OpenAudio, only freq, format, samples and channels are used by SDL_LoadWAV. We will detail these common members here.

freq

The number of samples sent to the sound device every second. Common values are 11025, 22050 and 44100. The higher the better.

format

Specifies the size and type of each sample element. Values it can take are:

AUDIO_U8

Unsigned 8-bit samples.

AUDIO_S8

Signed 8-bit samples.

AUDIO_U16 or AUDIO_U16LSB

not supported by all hardware (unsigned 16-bit little-endian)

AUDIO_S16 or AUDIO_S16LSB

not supported by all hardware (signed 16-bit little-endian)

AUDIO_U16MSB

not supported by all hardware (unsigned 16-bit big-endian)

AUDIO_S16MSB

not supported by all hardware (signed 16-bit big-endian)

AUDIO_U16SYS

Either AUDIO_U16LSB or AUDIO_U16MSB depending on hardware CPU endianness

AUDIO_S16SYS

Either AUDIO_S16LSB or AUDIO_S16MSB depending on hardware CPU endianness

channels

The number of separate sound channels. 1 is mono (single channel), 2 is stereo (dual channel).

samples

When used with SDL_OpenAudio this refers to the size of the audio buffer in samples. A sample is a chunk of audio data of the size specified in format multiplied by the number of channels. When the SDL_AudioSpec is used with SDL_LoadWAV samples is set to 4096.

See Also

SDL_OpenAudio, SDL_LoadWAV

SDL_AudioSpec (last edited 2008-04-17 08:18:09 by localhost)