Add libsamplerate for resampling decoder output

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+---
+layout: default
+---
+
+# Full API
+
+The full API consists of the following functions :
+
+```c
+SRC_STATE* src_new (int converter_type, int channels, int *error) ;
+SRC_STATE* src_delete (SRC_STATE *state) ;
+
+int src_process (SRC_STATE *state, SRC_DATA *data) ;
+int src_reset (SRC_STATE *state) ;
+int src_set_ratio (SRC_STATE *state, double new_ratio) ;
+```
+
+## Initialisation
+
+```c
+SRC_STATE* src_new (int converter_type, int channels, int *error) ;
+```
+
+The **src\_new** function returns an anonymous pointer to a sample rate
+converter object, src\_state. If an error occurs the function returns a
+NULL pointer and fills in the error value pointed to by the **error**
+pointer supplied by the caller. The converter must be one of the
+supplied converter types documented [here](api_misc.md#converters).
+
+## Cleanup
+
+```c
+SRC_STATE* src_delete (SRC_STATE *state) ;
+```
+
+The **src\_delete** function frees up all memory allocated for the given
+sample rate converter object and returns a NULL pointer. The caller is
+responsible for freeing any memory passed to the sample rate converter
+via the pointer to the **SRC\_DATA** struct.
+
+## Process
+
+```c
+int src_process (SRC_STATE *state, SRC_DATA *data) ;
+```
+
+The **src\_process** function processes the data provided by the caller
+in an **SRC\_DATA** struct using the sample rate converter object
+specified by the **SRC\_STATE** pointer. When operating on streaming
+data, this function can be called over and over again, with each new
+call providing new input data and returning new output data.
+
+The **SRC\_DATA** struct passed as the second parameter to the
+**src\_process** function has the following fields:
+
+```c
+typedef struct
+{   const float  *data_in;
+    float *data_out;
+
+    long   input_frames, output_frames ;
+    long   input_frames_used, output_frames_gen ;
+
+    int    end_of_input ;
+
+    double src_ratio ;
+} SRC_DATA ;
+```
+
+The fields of this struct which must be filled in by the caller are:
+
+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.
+
+end_of_input
+: Equal to 0 if more input data is available and 1 otherwise.
+
+Note that the data\_in and data\_out arrays may not overlap. If they do,
+the library will return an error code.
+
+When the **src\_process** function returns **output\_frames\_gen** will
+be set to the number of output frames generated and
+**input\_frames\_used** will be set to the number of input frames
+consumed to generate the provided number of output frames.
+
+The **src\_process** function returns non-zero if an error occurs. The
+non-zero error return value can be decoded into a text string using the
+function documented [here](api_misc.md#error-reporting).
+
+## Reset
+
+```c
+int src_reset (SRC_STATE *state) ;
+```
+
+The **src\_reset** function resets the internal state of the sample rate
+converter object to the same state it had immediately after its creation
+using **src\_new**. This should be called whenever a sample rate
+converter is to be used on two separate, unrelated pieces of audio.
+
+## Clone
+
+```c
+SRC_STATE* src_clone (SRC_STATE *state, int *error) ;
+```
+
+The **src_clone** function creates a copy of the internal state of the sample
+rate converter object. The output of the next call to **src\_process** will be
+identical for both the original and cloned state (given the same **SRC_DATA**
+input). This could be used to later resume sample rate conversion at a specific
+location in a stream with the same state, which may be useful in real-time
+applications.
+
+If an error occurs the function returns a NULL pointer and fills in the
+error value pointed to by the **error** pointer supplied by the caller.
+
+## Set Ratio
+
+```c
+int src_set_ratio (SRC_STATE *state, double new_ratio) ;
+```
+
+When using the **src_process** or **src_callback_process** APIs and updating the
+**src_ratio** field of the **SRC_STATE** struct, the library will try to
+smoothly transition between the conversion ratio of the last call and the
+conversion ratio of the current call.
+
+If the user wants to bypass this smooth transition and achieve a step response in
+the conversion ratio, the **src_set_ratio** function can be used to set the
+starting conversion ratio of the next call to **src_process** or
+**src_callback_process**.
+
+This function returns non-zero on error and the error return value can be
+decoded into a text string using the function documented [here](api_misc.md#error-reporting).