.TH "SDL_AudioCVT" "3" "Tue 11 Sep 2001, 22:58" "SDL" "SDL API Reference" 

.SH "NAME"

SDL_AudioCVT \- Audio Conversion Structure

.SH "STRUCTURE DEFINITION"

.PP

.nf

\f(CWtypedef struct{

  int needed;

  Uint16 src_format;

  Uint16 dest_format;

  double rate_incr;

  Uint8 *buf;

  int len;

  int len_cvt;

  int len_mult;

  double len_ratio;

  void (*filters[10])(struct SDL_AudioCVT *cvt, Uint16 format);

  int filter_index;

} SDL_AudioCVT;\fR

.fi

.PP

.SH "STRUCTURE DATA"

.TP 20

\fBneeded\fR

Set to one if the conversion is possible

.TP 20

\fBsrc_format\fR

Audio format of the source

.TP 20

\fBdest_format\fR

Audio format of the destination

.TP 20

\fBrate_incr\fR

Rate conversion increment

.TP 20

\fBbuf\fR

Audio buffer

.TP 20

\fBlen\fR

Length of the original audio buffer in bytes

.TP 20

\fBlen_cvt\fR

Length of converted audio buffer in bytes (calculated)

.TP 20

\fBlen_mult\fR

\fBbuf\fR must be \fBlen\fR*\fBlen_mult\fR bytes in size(calculated)

.TP 20

\fBlen_ratio\fR

Final audio size is \fBlen\fR*\fBlen_ratio\fR

.TP 20

\fBfilters[10](\&.\&.)\fR

Pointers to functions needed for this conversion

.TP 20

\fBfilter_index\fR

Current conversion function

.SH "DESCRIPTION"

.PP

The \fBSDL_AudioCVT\fR is used to convert audio data between different formats\&. A \fBSDL_AudioCVT\fR structure is created with the \fI\fBSDL_BuildAudioCVT\fP\fR function, while the actual conversion is done by the \fI\fBSDL_ConvertAudio\fP\fR function\&.

.PP

Many of the fields in the \fBSDL_AudioCVT\fR structure should be considered private and their function will not be discussed here\&.

.IP "\fBUint8 *\fP\fBbuf\fR" 10This points to the audio data that will be used in the conversion\&. It is both the source and the destination, which means the converted audio data overwrites the original data\&. It also means that the converted data may be larger than the original data (if you were converting from 8-bit to 16-bit, for instance), so you must ensure \fBbuf\fR is large enough\&. See below\&.

.IP "\fBint\fP \fBlen\fR" 10This is the length of the original audio data in bytes\&.

.IP "\fBint\fP \fBlen_mult\fR" 10As explained above, the audio buffer needs to be big enough to store the converted data, which may be bigger than the original audio data\&. The length of \fBbuf\fR should be \fBlen\fR*\fBlen_mult\fR\&.

.IP "\fBdouble\fP \fBlen_ratio\fR" 10When you have finished converting your audio data, you need to know how much of your audio buffer is valid\&. \fBlen\fR*\fBlen_ratio\fR is the size of the converted audio data in bytes\&. This is very similar to \fBlen_mult\fR, however when the convert audio data is shorter than the original \fBlen_mult\fR would be 1\&. \fBlen_ratio\fR, on the other hand, would be a fractional number between 0 and 1\&.

.SH "SEE ALSO"

.PP

\fI\fBSDL_BuildAudioCVT\fP\fR, \fI\fBSDL_ConvertAudio\fP\fR, \fI\fBSDL_AudioSpec\fR\fR

...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 22:58