dmG722Decode(3dm)					     dmG722Decode(3dm)

NAME    [Toc]    [Back]

     dmG722Decode - implements the ITU (International Telecommunication	Union)
     Recommendation G.722 decompression.

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/dm_audioutil.h>

     DMstatus dmG722Decode(DMG722decoder handle,
			  unsigned char	*ibuf, short *obuf, int	nsamples)

PARAMETER    [Toc]    [Back]

     handle    DMG722decoder structure,	created	by dmG722DecoderCreate(3dm),
	       specifies the signal processing parameters.


     ibuf      pointer to input	compressed data	buffer.	The data format	is
	       unsigned	char (8-bit).


     obuf      pointer to output sample	data buffer.  The data format is short
	       (16-bit).  The samples are assumed to be	two's complement.
	       Sampling	rate must be 16	kHz or less.


     nsamples  number of sample	in the input buffer to be processed. the value
	       of nsamples passed to the G.722 decode/decode routines must
	       always be a multiple of 2.  It will fail	if nsamples exceeds
	       the the maximum value specified when the	DMG722decoder was
	       created.

RETURNED VALUE    [Toc]    [Back]

     Returns DM_FAILURE	or DM_SUCCESS.

DESCRIPTION    [Toc]    [Back]

     dmG722Decode(3dm) implements the ITU Recommendation G.722 decompression.
     The mode for decoding operation can be 1, 2, or 3,	which correspond to
     64, 56 or 48 kbit/sec for audio coding and	0, 8 or	16 kbit/sec. for data.
     The mode is set by	dmG722DecoderCreate(3dm).


     see DESCRIPTION in	dmG722Encode(3dm) for the discussion of	filter delay
     and decompression of a part of compressed bit stream beginning in the
     middle of a compressed data file.








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dmG722Decode(3dm)					     dmG722Decode(3dm)



NOTE
     G.722 algorithm was developed for sampling	rate of	16 kHz.	 If sampling
     rate is less than 16 kHz, the algorithm still works, except the upper
     bits contains less	useful information.

SEE ALSO    [Toc]    [Back]

     dmG722DecoderCreate(3dm), dmG722DecoderDestroy(3dm), dmG722Encode(3dm),
     ITU Recommendations G.722.


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