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

     2 .SH "NAME"

     3 SDL_AudioCVT \- Audio Conversion Structure

     4 .SH "STRUCTURE DEFINITION"

     5 .PP

     6 .nf

     7 \f(CWtypedef struct{

     8   int needed;

     9   Uint16 src_format;

    10   Uint16 dest_format;

    11   double rate_incr;

    12   Uint8 *buf;

    13   int len;

    14   int len_cvt;

    15   int len_mult;

    16   double len_ratio;

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

    18   int filter_index;

    19 } SDL_AudioCVT;\fR

    20 .fi

    21 .PP

    22 .SH "STRUCTURE DATA"

    23 .TP 20

    24 \fBneeded\fR

    25 Set to one if the conversion is possible

    26 .TP 20

    27 \fBsrc_format\fR

    28 Audio format of the source

    29 .TP 20

    30 \fBdest_format\fR

    31 Audio format of the destination

    32 .TP 20

    33 \fBrate_incr\fR

    34 Rate conversion increment

    35 .TP 20

    36 \fBbuf\fR

    37 Audio buffer

    38 .TP 20

    39 \fBlen\fR

    40 Length of the original audio buffer in bytes

    41 .TP 20

    42 \fBlen_cvt\fR

    43 Length of converted audio buffer in bytes (calculated)

    44 .TP 20

    45 \fBlen_mult\fR

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

    47 .TP 20

    48 \fBlen_ratio\fR

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

    50 .TP 20

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

    52 Pointers to functions needed for this conversion

    53 .TP 20

    54 \fBfilter_index\fR

    55 Current conversion function

    56 .SH "DESCRIPTION"

    57 .PP

    58 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\&.

    59 .PP

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

    61 .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\&.

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

    63 .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\&.

    64 .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\&.

    65 .SH "SEE ALSO"

    66 .PP

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

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