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2 | <HTML> | |
3 | ||
4 | <HEAD> | |
5 | <TITLE> | |
6 | Secret Rabbit Code (aka libsamplerate) | |
7 | </TITLE> | |
8 | <META NAME="Author" CONTENT="Erik de Castro Lopo (erikd AT mega-nerd DOT com)"> | |
9 | <META NAME="Version" CONTENT="libsamplerate-0.1.8"> | |
10 | <META NAME="Description" CONTENT="The Secret Rabbit Code Home Page"> | |
11 | <META NAME="Keywords" CONTENT="libsamplerate sound resample audio dsp Linux"> | |
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21 | <BR> | |
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23 | <TABLE ALIGN="center" WIDTH="98%"> | |
24 | <TR> | |
25 | <TD VALIGN="top"> | |
26 | <BR> | |
27 | <DIV CLASS="nav"> | |
28 | <BR> | |
29 | <A HREF="index.html">Home</A><BR> | |
30 | <BR> | |
31 | <A HREF="api_simple.html">Simple API</A><BR> | |
32 | <A HREF="api_full.html">Full API</A><BR> | |
33 | <A HREF="api_callback.html">Callback API</A><BR> | |
34 | <A HREF="api_misc.html">Miscellaneous</A><BR> | |
35 | <A HREF="api_misc.html#ErrorReporting">Error Handling</A><BR> | |
36 | <BR> | |
37 | <DIV CLASS="block"> | |
38 | Author :<BR>Erik de Castro Lopo | |
39 | <!-- pepper --> | |
40 | <BR><BR> | |
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42 | ||
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44 | <IMG SRC= | |
45 | "/cgi-bin/Count.cgi?ft=6|frgb=55;55;55|tr=0|md=6|dd=B|st=1|sh=1|df=src_api.dat" | |
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48 | ||
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50 | <!-- pepper --> | |
51 | <!-- ######################################################################## --> | |
52 | <!-- pepper --> | |
53 | <TD VALIGN="top"> | |
54 | <DIV CLASS="block"> | |
55 | ||
56 | <H1><B>Simple API</B></H1> | |
57 | ||
58 | <P> | |
59 | <B>Important Note:</B> | |
60 | The simple API is not designed to work on small chunks of a larger piece of | |
61 | audio. | |
62 | If you attempt to use it this way you are doing it wrong and will not get the | |
63 | results you want. | |
64 | For processing audio data in chunks you <b>must</b> use the | |
65 | <a href="api_full.html">full api</a> | |
66 | or the | |
67 | <a href="api_callback.html">callback based api</a>. | |
68 | </P> | |
69 | ||
70 | <br/><br/> | |
71 | ||
72 | <P> | |
73 | The simple API consists of a single function : | |
74 | </P> | |
75 | <PRE> | |
76 | int src_simple (SRC_DATA *data, int converter_type, int channels) ; | |
77 | </PRE> | |
78 | <P> | |
79 | The use of this function rather than the more fully featured API requires the caller | |
80 | to know the total length of the input data before hand and that all input and output | |
81 | data can be held in the system's memory at once. | |
82 | It also assumes that there is a single constant ratio between input and output sample | |
83 | rates. | |
84 | <!-- | |
85 | If these conditions cannot be met, the full featured API should be used instead. | |
86 | In addition, this documentation is complemented by this | |
87 | <A HREF="ex_simple.html">example code</A>. --> | |
88 | </P> | |
89 | ||
90 | <P> | |
91 | Dealing with the easy stuff first, the <B>converter_type</B> parameter should be | |
92 | one of the values defined in <B>samplerate.h</B> and documented | |
93 | <A HREF="api_misc.html#Converters">here</A> while the <b>channels</b> parameter | |
94 | specifies the number of interleaved channels that the sample rate converter | |
95 | is being asked to process (number of input channels and output channels is always | |
96 | equal). | |
97 | There is no hard upper limit on the number of channels; it is limited purely | |
98 | by the amount of memory available. | |
99 | </P> | |
100 | ||
101 | ||
102 | <P> | |
103 | The first parameter to <B>src_simple</B> is a pointer to an <B>SRC_DATA</B> struct | |
104 | (more info <A HREF="api_misc.html#SRC_DATA">here</A>) defined as follows: | |
105 | </P> | |
106 | <PRE> | |
107 | typedef struct | |
108 | { float *data_in, *data_out ; | |
109 | ||
110 | long input_frames, output_frames ; | |
111 | long input_frames_used, output_frames_gen ; | |
112 | ||
113 | int end_of_input ; | |
114 | ||
115 | double src_ratio ; | |
116 | } SRC_DATA ; | |
117 | </PRE> | |
118 | <P> | |
119 | The fields of this struct which must be filled in by the caller are: | |
120 | </P> | |
121 | <PRE> | |
122 | data_in : A pointer to the input data samples. | |
123 | input_frames : The number of frames of data pointed to by data_in. | |
124 | data_out : A pointer to the output data samples. | |
125 | output_frames : Maximum number of frames pointer to by data_out. | |
126 | src_ratio : Equal to output_sample_rate / input_sample_rate. | |
127 | </PRE> | |
128 | <P> | |
129 | When the <B>src_simple</B> function returns <B>output_frames_gen</B> will be | |
130 | set to the number of output frames generated and <B>input_frames_used</B> will | |
131 | be set to the number of input frames used to generate the provided number of | |
132 | output frames. | |
133 | </P> | |
134 | <P> | |
135 | The <B>src_simple</B> function returns a non-zero value when an error occurs. | |
136 | See <A HREF="api_misc.html#ErrorReporting">here</A> for how to convert the error value into | |
137 | a text string. | |
138 | </P> | |
139 | ||
140 | </DIV> | |
141 | </TD></TR> | |
142 | </TABLE> | |
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145 | </HTML> | |
146 |