projects / audio-libsamplerate.git / blame
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1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
| 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"> | |
| 12 | <LINK REL=StyleSheet HREF="SRC.css" TYPE="text/css" MEDIA="all"> | |
| 13 | </HEAD> | |
| 14 | ||
| 15 | <BODY TEXT="#FFFFFF" BGCOLOR="#000000" LINK="#FB1465" VLINK="#FB1465" ALINK="#FB1465"> | |
| 16 | <!-- pepper --> | |
| 17 | <CENTER> | |
| 18 | <IMG SRC="SRC.png" HEIGHT=100 WIDTH=760 ALT="SRC.png"> | |
| 19 | </CENTER> | |
| 20 | <!-- pepper --> | |
| 21 | <BR> | |
| 22 | <!-- pepper --> | |
| 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> | |
| 41 | <!-- pepper --> | |
| 42 | ||
| 43 | </DIV> | |
| 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" | |
| 46 | HEIGHT=30 WIDTH=100 ALT="counter.gif"> | |
| 47 | </DIV> | |
| 48 | ||
| 49 | </TD> | |
| 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> | |
| 143 | ||
| 144 | </BODY> | |
| 145 | </HTML> | |
| 146 |