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280 Voice API for Windows Operating Systems Library Reference — November 2003
dx_listenecr( ) — enable echo cancellation resource mode
dx_listenecr( )
enable echo cancellation resource mode
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! Description
The dx_listenecr( ) function enables echo cancellation resource (ECR) mode on a specified voice
channel and connects the voice channel to the echo-referenced signal on the specified TDM bus
time slot. The TDM bus time slot information is contained in the SC_TSINFO data structure. For
more information on this structure, see SC_TSINFO, on page 529.
Note: The ECR functions have been replaced by the continuous speech processing (CSP) API functions.
CSP provides enhanced echo cancellation. For more information, see the Continuous Speech
Processing API Programming Guide and Continuous Speech Processing API Library Reference.
Note: For this function, NLP is enabled by default. If you do not want NLP enabled, use
dx_listenecrex( ) with NLP disabled.
The sc_numts field of the SC_TSINFO structure must be set to 1. The sc_tsarrayp field of the
SC_TSINFO structure must be initialized with a pointer to a valid array. The first element of this
array must contain a valid TDM bus time-slot number (between 0 and 1023) which was obtained
by issuing a call to xx_getxmitslot( ) (where xx_ is ag_, dt_, dx_, fx_, or ms_) or
dx_getxmitslotecr( ), depending on the application of the function. Upon return from the
dx_listenecr( ) function, the echo canceller of the specified voice channel is connected to the TDM
bus time slot specified, and it uses the signal carried on the TDM bus time slot as the echo-
reference signal for echo cancellation.
Name: int dx_listenecr(chdev, sc_tsinfop)
Inputs: int chdev
• handle of voice channel device on which echo cancellation is to
be performed
SC_TSINFO *sc_tsinfop
• pointer to TDM bus time slot information structure
Returns: 0 on success
-1 on error
Includes: srllib.h
dxxxlib.h
Category: Echo Cancellation Resource
Mode: synchronous
Platform: Springware
Parameter Description
chdev specifies the voice channel device handle obtained when the channel was
opened using dx_open( )
sc_tsinfop specifies a pointer to the SC_TSINFO structure