dmGSMDecode(3dm)					      dmGSMDecode(3dm)

NAME    [Toc]    [Back]

     dmGSMDecode - implements the European GSM 06.10 provisional standard for
     full-rate speech transcoding, prI-ETS 300 036, which uses RPE/LTP
     (regular pulse excitation/long term prediction) coding at 13 kbit/s.

SYNOPSIS    [Toc]    [Back]

     #include <dmedia/dm_audioutil.h>

     DMstatus dmGSMDecode(DMGSMdecoder handle,
			  unsigned char	*ibuf, short *obuf, int	numSamples)

PARAMETER    [Toc]    [Back]

     handle    DMGSMdecoder structure, created by dmGSMDecoderCreate(3dm),
	       specifies the signal processing parameters.


     ibuf      pointer to input	compressed data	buffer,	an array of a multiple
	       of 33 bytes. The	data format is unsigned	char (8-bit).


     obuf      pointer to output sample	data buffer, an	array of size of a
	       multiple	of 160.	 The data format is short (16-bit).  The
	       samples are assumed to be two's complement.  The	sampling rate
	       must be 8 kHz.


     numSamples
	       number of sample	in the output buffer to	be generated.  the
	       value of	numSamples passed to the GSM decode/decode routines
	       must always be a	multiple of 160.  The compressed bitstrem
	       buffer consists of a multiple of	33 bytes.

RETURNED VALUE    [Toc]    [Back]

     Returns DM_FAILURE	or DM_SUCCESS.

DESCRIPTION    [Toc]    [Back]

     dmGSMDecode(3dm) implements the GSM 06.10 decompression.

NOTE    [Toc]    [Back]

     The compressed bitrate now	is 13200 bits/s.  This is not the same as
     standard specification of 13000 bits/s because the	first 4	bits of	each
     33	byte are not useful information	bits.  This bits arrangement was
     adopted using the original	scheme by Jutta	Degener	(jutta@cs.tu-
     berlin.de)	and Carsten Bormann (cabo@cs.tu-berlin.de), Communications and
     Operating Systems Research	Group, TU Berlin for compatibility with
     typical UNIX applications.	 And may be modify later.



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dmGSMDecode(3dm)					      dmGSMDecode(3dm)



     GSM algorithm was developed for sampling rate of 8	kHz.

SEE ALSO    [Toc]    [Back]

     dmGSMDecoderCreate(3dm), dmGSMDecoderDestroy(3dm),	dmGSMEncode(3dm), ETSI
     GSM 06.10 standard.


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