dmG726Decode(3dm)dmG726Decode(3dm)NAMEdmG726Decode - implements ITU (International Telecommunication Union)
Recommendation G.726 ADPCM decompression for input compressed bit stream
of 40, 32 ,24, or 16 kbit/s and output data of 64 kbit/s A-law, mu-law,
or linear PCM. G.726 replaced G.721 and G.723.
SYNOPSIS
#include <dmedia/dm_audioutil.h>
DMstatus dmG726Decode(DMG726decoder handle,
unsigned char *inBuffer,
void *outBuffer,
int numSamples)
PARAMETER
handle DMG726decoder structure, created by dmG726DecoderCreate(3dm),
specifies the signal processing parameters.
ibuf pointer to input compressed data buffer, an array of bytes. The
data format is unsigned char (8-bit). The input bitstrem
buffer consists of a multiple of 1, 3, 1, or 5 bytes, for
operations at 16, 24, 32, or 40 kbit/s respectively.
obuf pointer to output sample data buffer, an array of short (16
bits) for linear output or unsigned char for A-law or mu-law
output. For linear output, samples are assumed to be two's
complement. Data buffer must be a multiple (the same multiple
as that of input bitstrem buffer) of 4, 8, 2, or 8 for
operations at 16, 24, 32, or 40 kbit/s respectively. This
assumes the sampling rate of 8 kHz.
numSamples
number of samples to be processed. it must always be a multiple
of 4, 8, 2, or 8 for operations at 16, 24, 32, or 40 kbit/s
respectively.
RETURNED VALUE
Returns DM_FAILURE or DM_SUCCESS.
DESCRIPTIONdmG726Decode(3dm) implements the ITU G.726 decompression. G.726
decompression decompresses 2, 3, 4, or 5 bits to generate one output
sample for 16, 24, 32, or 40 kbit/s operations respectively. 16, 24, 32,
or 40 kbit/s operation is indicated by setting parameter DM_AUDIO_BITRATE
to 16000, 24000, 32000, or 40000 using DMparams and passed to
Page 1
dmG726Decode(3dm)dmG726Decode(3dm)dmG726DecoderSetParams(3dm). Output format is indicated by setting
DM_G726_NATIVE_FORMAT to AUDIO_ENCODING_ULAW, AUDIO_ENCODING_ALAW, or
AUDIO_ENCODING_LINEAR, respectively for outputting mu-law, A-law, or
linear PCM data, using DMparams and passed to
dmG726DecoderSetParams(3dm). If output mode is AUDIO_ENCODING_LINEAR,
the PCM data type will be short. Otherwise, the PCM data type will be
unsigned char. Therefore, obuf is void in the function prototyping.
NOTE
G.726 algorithm was developed for sampling rate of 8 kHz, but could be
used from 8 kHz to 48 kHz.
SEE ALSOdmG726DecoderCreate(3dm), dmG726DecoderSetParams(3dm),
dmG726DecoderDestroy(3dm), dmG726Encode(3dm), ITU (International
Telecommunication Union) Recommendation G.726.
Page 2
