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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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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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47 | </DIV> | |
48 | ||
49 | </TD> | |
50 | <!-- pepper --> | |
51 | <!-- ######################################################################## --> | |
52 | <!-- pepper --> | |
53 | <TD VALIGN="top"> | |
54 | <DIV CLASS="block"> | |
55 | ||
56 | <H1><B>Full API</B></H1> | |
57 | <P> | |
58 | The full API consists of the following functions : | |
59 | </P> | |
60 | <PRE> | |
61 | SRC_STATE* <A HREF="#Init">src_new</A> (int converter_type, int channels, int *error) ; | |
62 | SRC_STATE* <A HREF="#CleanUp">src_delete</A> (SRC_STATE *state) ; | |
63 | ||
64 | int <A HREF="#Process">src_process</A> (SRC_STATE *state, SRC_DATA *data) ; | |
65 | int <A HREF="#Reset">src_reset</A> (SRC_STATE *state) ; | |
66 | int <A HREF="#SetRatio">src_set_ratio</A> (SRC_STATE *state, double new_ratio) ; | |
67 | </PRE> | |
68 | ||
69 | <A NAME="Init"></A> | |
70 | <H3><BR>Initialisation</H3> | |
71 | <PRE> | |
72 | SRC_STATE* src_new (int converter_type, int channels, int *error) ; | |
73 | </PRE> | |
74 | <P> | |
75 | The <B>src_new</B> function returns an anonymous pointer to a sample rate | |
76 | converter object, src_state. | |
77 | If an error occurs the function returns a NULL pointer and fills in the | |
78 | error value pointed to by the <B>error</B> pointer supplied by the caller. | |
79 | The converter must be one of the supplied converter types documented | |
80 | <A HREF="api_misc.html#Converters">here</A>. | |
81 | </P> | |
82 | ||
83 | <A NAME="CleanUp"></A> | |
84 | <H3><BR>Cleanup</H3> | |
85 | <PRE> | |
86 | SRC_STATE* src_delete (SRC_STATE *state) ; | |
87 | </PRE> | |
88 | <P> | |
89 | The <B>src_delete</B> function frees up all memory allocated for the given sample | |
90 | rate converter object and returns a NULL pointer. | |
91 | The caller is responsible for freeing any memory passed to the sample rate converter | |
92 | via the pointer to the <B>SRC_DATA</B> struct. | |
93 | </P> | |
94 | ||
95 | <A NAME="Process"></A> | |
96 | <H3><BR>Process</H3> | |
97 | <PRE> | |
98 | int src_process (SRC_STATE *state, SRC_DATA *data) ; | |
99 | </PRE> | |
100 | <P> | |
101 | The <B>src_process</B> function processes the data provided by the caller | |
102 | in an <B>SRC_DATA</B> struct using the sample rate converter object specified | |
103 | by the <B>SRC_STATE</B> pointer. | |
104 | When operating on streaming data, this function can be called over and over again, | |
105 | with each new call providing new input data and returning new output data. | |
106 | </P> | |
107 | ||
108 | <P> | |
109 | The <B>SRC_DATA</B> struct passed as the second parameter to the <B>src_process</B> | |
110 | function has the following fields: | |
111 | </P> | |
112 | <PRE> | |
113 | typedef struct | |
114 | { float *data_in, *data_out ; | |
115 | ||
116 | long input_frames, output_frames ; | |
117 | long input_frames_used, output_frames_gen ; | |
118 | ||
119 | int end_of_input ; | |
120 | ||
121 | double src_ratio ; | |
122 | } SRC_DATA ; | |
123 | </PRE> | |
124 | <P> | |
125 | The fields of this struct which must be filled in by the caller are: | |
126 | </P> | |
127 | <PRE> | |
128 | data_in : A pointer to the input data samples. | |
129 | input_frames : The number of frames of data pointed to by data_in. | |
130 | data_out : A pointer to the output data samples. | |
131 | output_frames : Maximum number of frames pointer to by data_out. | |
132 | src_ratio : Equal to output_sample_rate / input_sample_rate. | |
133 | end_of_input : Equal to 0 if more input data is available and 1 | |
134 | otherwise. | |
135 | </PRE> | |
136 | <P> | |
137 | Note that the data_in and data_out arrays may not overlap. If they do, the | |
138 | library will return an error code. | |
139 | </P> | |
140 | <P> | |
141 | When the <B>src_process</B> function returns <B>output_frames_gen</B> will be | |
142 | set to the number of output frames generated and <B>input_frames_used</B> will | |
143 | be set to the number of input frames consumed to generate the provided number of | |
144 | output frames. | |
145 | </P> | |
146 | ||
147 | <P> | |
148 | The <B>src_process</B> function returns non-zero if an error occurs. | |
149 | The non-zero error return value can be decoded into a text string using the function | |
150 | documented <A HREF="api_misc.html#ErrorReporting">here</A>. | |
151 | </P> | |
152 | ||
153 | <A NAME="Reset"></A> | |
154 | <H3><BR>Reset</H3> | |
155 | <PRE> | |
156 | int src_reset (SRC_STATE *state) ; | |
157 | </PRE> | |
158 | <P> | |
159 | The <B>src_reset</B> function resets the internal state of the sample rate | |
160 | converter object to the same state it had immediately after its creation using | |
161 | <B>src_new</B>. | |
162 | This should be called whenever a sample rate converter is to be used on two | |
163 | separate, unrelated pieces of audio. | |
164 | </P> | |
165 | ||
166 | <A NAME="SetRatio"></A> | |
167 | <H3><BR>Set Ratio</H3> | |
168 | <PRE> | |
169 | int src_set_ratio (SRC_STATE *state, double new_ratio) ; | |
170 | </PRE> | |
171 | ||
172 | <p> | |
173 | When using the <B>src_process</B> or <B>src_callback_process</B> APIs and | |
174 | updating the <B>src_ratio</B> field of the <B>SRC_STATE</B> struct, the library | |
175 | will try to smoothly transition between the conversion ratio of the last call | |
176 | and the conversion ratio of the current call. | |
177 | <p/> | |
178 | ||
179 | <P> | |
180 | If the user want to bypass this smooth transition and achieve a step response in | |
181 | the conversion ratio, the <B>src_set_ratio</B> function can be used to set the | |
182 | starting conversion ratio of the next call to <B>src_process</B> or | |
183 | <B>src_callback_process</B>. | |
184 | <p/> | |
185 | ||
186 | <P> | |
187 | This function returns non-zero on error and the error return value can be | |
188 | decoded into a text string using the function documented | |
189 | <A HREF="api_misc.html#ErrorReporting">here</A>.</P> | |
190 | ||
191 | <!-- <A HREF="mailto:aldel@mega-nerd.com">For the spam bots</A> --> | |
192 | ||
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