dmFS1016Decode(3dm)					   dmFS1016Decode(3dm)

NAME    [Toc]    [Back]

     dmFS1016Decode - implements the US	Federal	Standard 1016 4800/7200/9600
     bits/s CELP (Code Excited Linear Predictive) Voice	Coder.

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/dmedia.h>
     #include <dmedia/dm_params.h>
     #include <dmedia/dm_audioutil.h>

     DMstatus dmFS1016Decode(DMFS1016decoder handle,
			  unsigned char	*ibuf, short *obuf, int	nsamples)

PARAMETER    [Toc]    [Back]

     handle    DMFS1016decoder structure, created by
	       dmFS1016DecoderCreate(3dm), specifies the signal	processing
	       parameters.


     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.

RETURNED VALUE    [Toc]    [Back]

     Returns DM_FAILURE	or DM_SUCCESS.

DESCRIPTION    [Toc]    [Back]

     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_7200_BITS
     DM_FS1016_9600_BITS

     DM_FS1016_POSTFILTERING_YES    [Toc]    [Back]
     DM_FS1016_POSTFILTERING_NO




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dmFS1016Decode(3dm)					   dmFS1016Decode(3dm)



     and

     DM_FS1016_HIGHPASS_YES    [Toc]    [Back]
     DM_FS1016_HIGHPASS_NO



     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
     DM_FS1016_HIGHPASS_NO.


     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.

NOTE    [Toc]    [Back]

     FS1016 algorithm was developed for	sampling rate of 8 kHz.

SEE ALSO    [Toc]    [Back]

     dmFS1016DecoderCreate(3dm), dmFS1016DecoderDestroy(3dm),
     dmFS1016Encode(3dm), dmFS1016DecoderSetParams(3dm), Federal Standard
     1016.


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