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1 .TH "SDL_AudioCVT" "3" "Mon 12 Mar 2001, 01:02" "SDL" "SDL API Reference"
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2 .SH "NAME"
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3 SDL_AudioCVT\- Audio Conversion Structure
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4 .SH "STRUCTURE DEFINITION"
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5 .PP
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6 .nf
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7 \f(CWtypedef struct{
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8 int needed;
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9 Uint16 src_format;
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10 Uint16 dest_format;
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11 double rate_incr;
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12 Uint8 *buf;
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13 int len;
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14 int len_cvt;
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15 int len_mult;
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16 double len_ratio;
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17 void (*filters[10])(struct SDL_AudioCVT *cvt, Uint16 format);
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18 int filter_index;
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19 } SDL_AudioCVT;\fR
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20 .fi
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21 .PP
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22 .SH "STRUCTURE DATA"
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23 .TP 20
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24 \fBneeded\fR
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25 Set to one if the conversion is possible
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26 .TP 20
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27 \fBsrc_format\fR
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28 Audio format of the source
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29 .TP 20
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30 \fBdest_format\fR
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31 Audio format of the destination
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32 .TP 20
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33 \fBrate_incr\fR
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34 Rate conversion increment
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35 .TP 20
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36 \fBbuf\fR
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37 Audio buffer
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38 .TP 20
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39 \fBlen\fR
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40 Length of the original audio buffer in bytes
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41 .TP 20
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42 \fBlen_cvt\fR
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43 Length of converted audio buffer in bytes (calculated)
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44 .TP 20
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45 \fBlen_mult\fR
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46 \fBbuf\fR must be \fBlen\fR*\fBlen_mult\fR bytes in size(calculated)
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47 .TP 20
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48 \fBlen_ratio\fR
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49 Final audio size is \fBlen\fR*\fBlen_ratio\fR
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50 .TP 20
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51 \fBfilters[10](\&.\&.)\fR
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52 Pointers to functions needed for this conversion
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53 .TP 20
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54 \fBfilter_index\fR
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55 Current conversion function
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56 .SH "DESCRIPTION"
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57 .PP
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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\&.
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59 .PP
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60 Many of the fields in the \fBSDL_AudioCVT\fR structure should be considered private and their function will not be discussed here\&.
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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\&.
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62 .IP "\fBint\fP \fBlen\fR" 10This is the length of the original audio data in bytes\&.
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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\&.
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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\&.
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65 .SH "SEE ALSO"
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66 .PP
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67 \fI\fBSDL_BuildAudioCVT\fP\fR, \fI\fBSDL_ConvertAudio\fP\fR, \fI\fBSDL_AudioSpec\fR\fR
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68 ...\" created by instant / docbook-to-man, Mon 12 Mar 2001, 01:02
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