Mercurial > sdl-ios-xcode

view docs/man3/SDL_AudioSpec.3 @ 1542:a8bf1aa21020

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Fixed bug #15 SDL_blit_A.mmx-speed.patch.txt -- Speed improvements and a bugfix for the current GCC inline mmx asm code: - Changed some ops and removed some resulting useless ones. - Added some instruction parallelism (some gain) The resulting speed on my Xeon improved upto 35% depending on the function (measured in fps). - Fixed a bug where BlitRGBtoRGBSurfaceAlphaMMX() was setting the alpha component on the destination surfaces (to opaque-alpha) even when the surface had none. SDL_blit_A.mmx-msvc.patch.txt -- MSVC mmx intrinsics version of the same GCC asm code. MSVC compiler tries to parallelize the code and to avoid register stalls, but does not always do a very good job. Per-surface blending MSVC functions run quite a bit faster than their pure-asm counterparts (upto 55% faster for 16bit ones), but the per-pixel blending runs somewhat slower than asm. - BlitRGBtoRGBSurfaceAlphaMMX and BlitRGBtoRGBPixelAlphaMMX (and all variants) can now also handle formats other than (A)RGB8888. Formats like RGBA8888 and some quite exotic ones are allowed -- like RAGB8888, or actually anything having channels aligned on 8bit boundary and full 8bit alpha (for per-pixel alpha blending). The performance cost of this change is virtually 0 for per-surface alpha blending (no extra ops inside the loop) and a single non-MMX op inside the loop for per-pixel blending. In testing, the per-pixel alpha blending takes a ~2% performance hit, but it still runs much faster than the current code in CVS. If necessary, a separate function with this functionality can be made. This code requires Processor Pack for VC6.
author Sam Lantinga <slouken@libsdl.org>
date Wed, 15 Mar 2006 15:39:29 +0000
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