dmAudioRateConverterGetParams(3dm)dmAudioRateConverterGetParams(3dm)NAMEdmAudioRateConverterGetParams - get rate converter parameter values
SYNOPSIS
#include <dmedia/dm_audioutil.h>
#include <dmedia/dm_audio.h>
#include <dmedia/dm_params.h>
DMstatus dmAudioRateConverterGetParams(DMaudiorateconverter handle,
DMparams *params)
PARAMETER
handle DMaudiorateconverter structure, created by
dmAudioRateConverterCreate(3dm).
params List of parameters for query.
RETURNED VALUE
Returns DM_SUCCESS or DM_FAILURE.
DESCRIPTIONdmAudioRateConverterGetParams(3dm) gets state of converter with params.
The set of parameters of params for query are, defined in
dmedia/dm_audioutil.h:
DM_AUDIO_RC_ATOMIC_IN_LENGTH
DM_AUDIO_RC_ATOMIC_OUT_LENGTH
DM_AUDIO_RC_GROUP_DELAY
The rate convert algorithm processes blocks of a fixed length determined
by the conversion process parameters. The input and output lengths must
be a multiple of DM_AUDIO_RC_ATOMIC_IN_LENGTH and
DM_AUDIO_RC_ATOMIC_OUT_LENGTH, respectively. See further description in
dmAudioRateConvert(3dm).
DM_AUDIO_RC_GROUP_DELAY measured in output samples. These sampling rate
conversion algorithms use filter operations that convolve a N past input
samples with a filter M-coefficient array to create N+M-1 output samples.
Note that the filtered signal contains more samples than the unfiltered
signal.
We use linear phase filters with a constant group delay G = (M-1)/2
samples. In real time operation, convolution simply delays the output by
G samples. In file conversion expecting N samples in and out, the output
signal is offset by G samples from the first sample thus omits the last G
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dmAudioRateConverterGetParams(3dm)dmAudioRateConverterGetParams(3dm)
samples from the output file. Multiple conversions compound the delays
and data loss.
SGI audio applications manage the above problems by omitting the first G
samples while computing more than N+G samples. In practice, G is rounded
to the nearest sample and thus sample time alignment is occasionally
ahead or behind one sample. G specifies the number of output samples to
omit.
NOTESEE ALSOdmAudioRateConverterCreate(3dm), dmAudioRateConverterSetParams(3dm),
dmAudioRateConvert(3dm).
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