dmAudioRateConvert(3dm)dmAudioRateConvert(3dm)NAMEdmAudioRateConvert - convert data sampling rate. It consumes an input
buffer of floats and generates an output buffer of floats.
SYNOPSIS
#include <dmedia/dm_audioutil.h>
DMstatus dmAudioRateConvert(DMaudiorateconverter handle,
float *inbuf, float *outbuf, int inlen,
int *numout)
PARAMETER
handle DMaudiorateconverter structure, created by
dmAudioRateConverterCreate(3dm), specifies the signal
processing parameters.
inbuf pointer to input data buffer. The converter does not alter the
contents of this buffer. The data format is currently limited
to single channel, 32-bit floating point.
outbuf pointer to output data buffer. Ensure that inbuf and outbuf do
not overlap. The data format is currently limited to single
channel, 32-bit floating point. Sampling rate conversion
alters the length of the data. dmAudioRateConvert will output
inlen * (output rate / input rate) samples.
inlen length of the input buffer must be a multiple of
DM_AUDIO_RC_ATOMIC_IN_LENGTH, dependent on the conversion
parameters and can be acquired with dmParamsGetInt(3dm),
dmAudioRateConverterSetParams(3dm), or
dmAudioRateConverterGetParams(3dm).
numout # input sample frames numout this iteration, pass by reference.
null (0) value ok.
RETURNED VALUE
Returns DM_FAILURE or DM_SUCCESS.
DESCRIPTIONdmAudioRateConvert(3dm) attempts to convert inlen samples. inlen must be
of a multiple M of DM_AUDIO_RC_ATOMIC_IN_LENGTH. The application program
must malloc DM_AUDIO_RC_ATOMIC_IN_LENGTH * M samples for inbuf and
DM_AUDIO_RC_ATOMIC_OUT_LENGTH * M samples for outbuf for any M >= 1
(chosen by the application). DM_AUDIO_RC_ATOMIC_IN_LENGTH * M samples
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dmAudioRateConvert(3dm)dmAudioRateConvert(3dm)
are numout into DM_AUDIO_RC_ATOMIC_OUT_LENGTH * M samples. The actual
value of samples returned in outbuf by a given call to dmAudioRateConvert
may be slightly less than DM_AUDIO_RC_ATOMIC_OUT_LENGTH * M, and is
returned in numout. dmAudioRateConvert will return DM_FAILURE if it is
called with a value of "inlen" which is not a multiple M of
DM_AUDIO_RC_ATOMIC_IN_LENGTH. It will return DM_SUCCESS in all other
cases.
The application will want to discard the first DM_AUDIO_RC_GROUP_DELAY
samples returned in outbuf from dmAudioRateConvert. See further
discussion in dmAudioRateConverterGetParams(3dm).
The application may want to flush out an additional
DM_AUDIO_RC_GROUP_DELAY samples from dmAudioRateConvert after feeding in
all the input data to be converted. This flushing operation is performed
by calling dmAudioRateConvert with a value inlen = h *
DM_AUDIO_RC_ATOMIC_IN_LENGTH where inlen >= DM_AUDIO_RC_GROUP_DELAY (the
corresponding inbuf will typically be bzero'd, although the values in
inbuf probably don't matter).
To clear the internal buffers used converter, call
dmAudioRateConverterReset(3dm).
NOTESEE ALSOdmParamsGetFloat(3dm), dmAudioRateConverterSetParams(3dm),
dmAudioRateConverterGetParams(3dm), dmAudioRateConverterReset(3dm).
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