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| Secret Rabbit Code (aka libsamplerate) |
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| <A HREF="index.html">Home</A><BR> |
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| <A HREF="api_simple.html">Simple API</A><BR> |
| <A HREF="api_full.html">Full API</A><BR> |
| <A HREF="api_callback.html">Callback API</A><BR> |
| <A HREF="api_misc.html">Miscellaneous</A><BR> |
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| Author :<BR>Erik de Castro Lopo |
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| <H1><B>Simple API</B></H1> |
| |
| <P> |
| <B>Important Note:</B> |
| The simple API is not designed to work on small chunks of a larger piece of |
| audio. |
| If you attempt to use it this way you are doing it wrong and will not get the |
| results you want. |
| For processing audio data in chunks you <b>must</b> use the |
| <a href="api_full.html">full api</a> |
| or the |
| <a href="api_callback.html">callback based api</a>. |
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| <br/><br/> |
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| <P> |
| The simple API consists of a single function : |
| </P> |
| <PRE> |
| int src_simple (SRC_DATA *data, int converter_type, int channels) ; |
| </PRE> |
| <P> |
| The use of this function rather than the more fully featured API requires the caller |
| to know the total length of the input data before hand and that all input and output |
| data can be held in the system's memory at once. |
| It also assumes that there is a single constant ratio between input and output sample |
| rates. |
| <!-- |
| If these conditions cannot be met, the full featured API should be used instead. |
| In addition, this documentation is complemented by this |
| <A HREF="ex_simple.html">example code</A>. --> |
| </P> |
| |
| <P> |
| Dealing with the easy stuff first, the <B>converter_type</B> parameter should be |
| one of the values defined in <B>samplerate.h</B> and documented |
| <A HREF="api_misc.html#Converters">here</A> while the <b>channels</b> parameter |
| specifies the number of interleaved channels that the sample rate converter |
| is being asked to process (number of input channels and output channels is always |
| equal). |
| There is no hard upper limit on the number of channels; it is limited purely |
| by the amount of memory available. |
| </P> |
| |
| |
| <P> |
| The first parameter to <B>src_simple</B> is a pointer to an <B>SRC_DATA</B> struct |
| (more info <A HREF="api_misc.html#SRC_DATA">here</A>) defined as follows: |
| </P> |
| <PRE> |
| typedef struct |
| { float *data_in, *data_out ; |
| |
| long input_frames, output_frames ; |
| long input_frames_used, output_frames_gen ; |
| |
| int end_of_input ; |
| |
| double src_ratio ; |
| } SRC_DATA ; |
| </PRE> |
| <P> |
| The fields of this struct which must be filled in by the caller are: |
| </P> |
| <PRE> |
| data_in : A pointer to the input data samples. |
| input_frames : The number of frames of data pointed to by data_in. |
| data_out : A pointer to the output data samples. |
| output_frames : Maximum number of frames pointer to by data_out. |
| src_ratio : Equal to output_sample_rate / input_sample_rate. |
| </PRE> |
| <P> |
| When the <B>src_simple</B> function returns <B>output_frames_gen</B> will be |
| set to the number of output frames generated and <B>input_frames_used</B> will |
| be set to the number of input frames used to generate the provided number of |
| output frames. |
| </P> |
| <P> |
| The <B>src_simple</B> function returns a non-zero value when an error occurs. |
| See <A HREF="api_misc.html#ErrorReporting">here</A> for how to convert the error value into |
| a text string. |
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