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Initial revision
author Sam Lantinga <slouken@lokigames.com>
date Thu, 26 Apr 2001 16:45:43 +0000
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1 .TH "SDL_AudioCVT" "3" "Mon 12 Mar 2001, 01:02" "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, Mon 12 Mar 2001, 01:02