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Current libsamplerate source
author Chris Cannam
date Tue, 18 Oct 2016 13:24:45 +0100
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40:1df64224f5ac 41:481f5f8c5634
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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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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
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40 <BR><BR>
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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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