lowcfe.cc

Reference Implementation of G.711 standard and other voice codecs

/*                                                          24.May.2005 v.1.0
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                    ITU-T - USER'S GROUP ON SOFTWARE TOOLS
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       =============================================================
       COPYRIGHT NOTE: This source code, and all of its derivations,
       is subject to the "ITU-T General Public License". Please have
       it  read  in    the  distribution  disk,   or  in  the  ITU-T
       Recommendation G.191 on "SOFTWARE TOOLS FOR SPEECH AND  AUDIO 
       CODING STANDARDS".
	         ** This code has  (C) Copyright by AT&T Corp. **
       =============================================================


MODULE:         G.711 Appendix I PLC module.

ORIGINAL BY:    AT&T Corp.

FUNCTIONS:

g711plc_construct: ...... LowcFE Constructor.

g711plc_dofe: ........... Generate the synthetic signal.
						  At the beginning of an erasure determine the pitch, and extract
						  one pitch period from the tail of the signal. Do an OLA for 1/4
						  of the pitch to smooth the signal. Then repeat the extracted signal
						  for the length of the erasure. If the erasure continues for more than
						  10 msec, increase the number of periods in the pitchbuffer. At the end
						  of an erasure, do an OLA with the start of the first good frame.
						  The gain decays as the erasure gets longer.

g711plc_addtohistory: ... A good frame was received and decoded.
						  If right after an erasure, do an overlap add with the synthetic signal.
						  Add the frame to history buffer.

HISTORY:

  24.May.05  v1.0  Release of 1st G711 PLC module <AT&T>.
				   Integration of this module in STL2005 <Cyril Guillaum