dmFS1016Decode - implements the US Federal Standard 1016 4800/7200/9600
bits/s CELP (Code Excited Linear Predictive) Voice Coder.
DMstatus dmFS1016Decode(DMFS1016decoder handle,
unsigned char *ibuf, short *obuf, int nsamples)
handle DMFS1016decoder structure, created by
dmFS1016DecoderCreate(3dm), specifies the signal processing
ibuf pointer to input compressed data buffer. The data format is
unsigned char (8-bit). This bitstream buffer must consist of a
multiple of 18 bytes.
obuf pointer to output sample data buffer. The data format is short
(16-bit). The samples are assumed to be two's complement. The
sampling rate must be 8 kHz.
nsamples number of sample in the output buffer to be generated. The
value of nsamples passed to the FS1016 decode/decode routines
must always be a multiple of 240, 160, or 120 for operations of
4800, 7200, or 9600 bits/s respectively.
Returns DM_FAILURE or DM_SUCCESS.
dmFS1016Decode(3dm) implements the Federal Standard 1016 decompression.
The uncompressed data sampling rate is 8000 Hz. The compression bitrate
and modes for decoding operation can be
DM_FS1016_4800_BITS [Toc] [Back]
DM_FS1016_POSTFILTERING_YES [Toc] [Back]
DM_FS1016_HIGHPASS_YES [Toc] [Back]
that select a decoder with or without postfiltering and highpass
filtering. Cautious application of postfiltering at the decoder's output
is recommended. The human ear's masking properties are exploited to
trade off speech distortion vs. quantizing noise. In tandem coding
scenarios, only one stage of postfiltering is recommended and multiple
stages should be avoided. The bitrate and decode mode are set by a call
to dmFS1016DecoderSetParams(3dm). Without calling
dmFS1016DecoderSetParams(3dm), decoder sets defaults to
DM_FS1016_4800_BITS, DM_FS1016_POSTFILTERING_YES, and
see DESCRIPTION in dmFS1016Encode(3dm) for the discussion of
decompression of a part of compressed bit stream beginning in the middle
of a compressed data file.
FS1016 algorithm was developed for sampling rate of 8 kHz.
dmFS1016Encode(3dm), dmFS1016DecoderSetParams(3dm), Federal Standard
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