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First shot at new audio data types (int32 and float32). Notable changes: - Converters between types are autogenerated. Instead of making multiple passes over the data with seperate filters for endianess, size, signedness, etc, converting between data types is always one specialized filter. This simplifies SDL_BuildAudioCVT(), which otherwise had a million edge cases with the new types, and makes the actually conversions more CPU cache friendly. Left a stub for adding specific optimized versions of these routines (SSE/MMX/Altivec, assembler, etc) - Autogenerated converters are built by SDL/src/audio/sdlgenaudiocvt.pl. This does not need to be run unless tweaking the code, and thus doesn't need integration into the build system. - Went through all the drivers and tried to weed out all the "Uint16" references that are better specified with the new SDL_AudioFormat typedef. - Cleaned out a bunch of hardcoded bitwise magic numbers and replaced them with new SDL_AUDIO_* macros. - Added initial float32 and int32 support code. Theoretically, existing drivers will push these through converters to get the data they want to feed to the hardware. Still TODO: - Optimize and debug new converters. - Update the CoreAudio backend to accept float32 data directly. - Other backends, too? - SDL_LoadWAV() needs to be updated to support int32 and float32 .wav files (both of which exist and can be generated by 'sox' for testing purposes). - Update the mixer to handle new datatypes. - Optionally update SDL_sound and SDL_mixer, etc.
author Ryan C. Gordon <icculus@icculus.org>
date Thu, 24 Aug 2006 12:10:46 +0000 (2006-08-24)
parents e5bc29de3f0a
children 546f7c1eb755
line wrap: on
line source
.TH "SDL_AudioSpec" "3" "Tue 11 Sep 2001, 22:58" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_AudioSpec\- Audio Specification Structure
.SH "STRUCTURE DEFINITION"
.PP
.nf
\f(CWtypedef 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;\fR
.fi
.PP
.SH "STRUCTURE DATA"
.TP 20
\fBfreq\fR
Audio frequency in samples per second
.TP 20
\fBformat\fR
Audio data format
.TP 20
\fBchannels\fR
Number of channels: 1 mono, 2 stereo
.TP 20
\fBsilence\fR
Audio buffer silence value (calculated)
.TP 20
\fBsamples\fR
Audio buffer size in samples
.TP 20
\fBsize\fR
Audio buffer size in bytes (calculated)
.TP 20
\fBcallback(\&.\&.)\fR
Callback function for filling the audio buffer
.TP 20
\fBuserdata\fR
Pointer the user data which is passed to the callback function
.SH "DESCRIPTION"
.PP
The \fBSDL_AudioSpec\fR structure is used to describe the format of some audio data\&. This structure is used by \fI\fBSDL_OpenAudio\fP\fR and \fI\fBSDL_LoadWAV\fP\fR\&. While all fields are used by \fBSDL_OpenAudio\fP only \fBfreq\fR, \fBformat\fR, \fBsamples\fR and \fBchannels\fR are used by \fBSDL_LoadWAV\fP\&. We will detail these common members here\&.
.TP 20
\fBfreq\fR
The number of samples sent to the sound device every second\&. Common values are 11025, 22050 and 44100\&. The higher the better\&.
.TP 20
\fBformat\fR
Specifies the size and type of each sample element 
.IP "\fBAUDIO_U8\fP" 10Unsigned 8-bit samples
.IP "\fBAUDIO_S8\fP" 10Signed 8-bit samples
.IP "\fBAUDIO_U16\fP or \fBAUDIO_U16LSB\fP" 10Unsigned 16-bit little-endian samples
.IP "\fBAUDIO_S16\fP or \fBAUDIO_S16LSB\fP" 10Signed 16-bit little-endian samples
.IP "\fBAUDIO_U16MSB\fP" 10Unsigned 16-bit big-endian samples
.IP "\fBAUDIO_S16MSB\fP" 10Signed 16-bit big-endian samples
.IP "\fBAUDIO_U16SYS\fP" 10Either \fBAUDIO_U16LSB\fP or \fBAUDIO_U16MSB\fP depending on you systems endianness
.IP "\fBAUDIO_S16SYS\fP" 10Either \fBAUDIO_S16LSB\fP or \fBAUDIO_S16MSB\fP depending on you systems endianness
.TP 20
\fBchannels\fR
The number of seperate sound channels\&. 1 is mono (single channel), 2 is stereo (dual channel)\&.
.TP 20
\fBsamples\fR
When used with \fI\fBSDL_OpenAudio\fP\fR this refers to the size of the audio buffer in samples\&. A sample a chunk of audio data of the size specified in \fBformat\fR mulitplied by the number of channels\&. When the \fBSDL_AudioSpec\fR is used with \fI\fBSDL_LoadWAV\fP\fR \fBsamples\fR is set to 4096\&.
.SH "SEE ALSO"
.PP
\fI\fBSDL_OpenAudio\fP\fR, \fI\fBSDL_LoadWAV\fP\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 22:58