function enables and disables the detection of media modes on the specified
call. When a media mode is detected, a message is sent to the application.
| HCALL hCall,
| DWORD dwMediaModes
A handle to the call. The call state of hCall
can be any state except idle
The media modes to be monitored. A value of zero for the dwMediaModes
parameter cancels all media mode detection. This parameter can have multiple
flags set. This parameter uses the following LINEMEDIAMODE_ constants:
The application wants to handle calls of the interactive voice media type (it
manages live voice calls).
Voice energy is present on the call and the voice is locally handled by an
The application wants to handle calls with the data modem media mode.
The application wants to handle calls of the group 3 fax media type.
The application wants to handle calls with the TDD (Telephony Devices for the
Deaf) media mode.
The application wants to handle calls of the group 4 fax media type.
The application wants to handle calls of the digital data media type
The application wants to handle calls with the teletex media mode.
The application wants to handle calls with the videotex media mode.
The application wants to handle calls with the telex media mode.
The application wants to handle calls with the ISDN mixed media mode.
The application wants to handle calls with the ADSI (Analog Display Services
Interface) media mode.
The media mode of the call is VoiceView.
Returns zero if the request is successful or a negative error number if an
error has occurred. Possible return values are:
LINEERR_INVALCALLHANDLE, LINEERR_OPERATIONUNAVAIL, LINEERR_INVALCALLSTATE,
LINEERR_OPERATIONFAILED, LINEERR_INVALMEDIAMODE, LINEERR_RESOURCEUNAVAIL,
The media modes specified with lineOpen
relate only to enabling the detection of these media modes by the service
provider for the purpose of handing off new incoming calls to the proper
application. They do not impact any of the media-mode notification messages that are
expected because of a previous invocation of lineMonitorMedia
This function is considered successful if media-mode monitoring has been
correctly initiated, not when media mode monitoring has terminated. Media monitoring
for a given media mode remains in effect until it is explicitly disabled by
with a dwMediaModes
parameter set to zero, until the call transitions to idle
, or when the application deallocates its call handle for the call. The lineMonitorMedia
function is primarily an event reporting mechanism. The media mode of call,
as indicated in LINECALLINFO
, is not affected by the service provider's detection of the media mode. Only
the controlling application can change a call's media mode.
Default media monitoring performed by the service provider corresponds to the
union of all media modes specified on lineOpen
Although this function can be invoked in any call state, a call's media mode
can typically only be detected while the call is in certain call states. These
states may be device specific. For example, in ISDN, a message may indicate the
media mode of the media stream before the media stream exists. Similarly,
distinctive ringing or the called ID information about the call can be used to
identify the media mode of a call. Otherwise, the call may have to be answered (call
in the connected
state) to allow a service provider to determine the call's media mode by
filtering the media stream. Because filtering a call's media stream implies a
computational overhead, applications should disable media monitoring when not
required. By default, media monitoring is enabled for newly inbound calls, because a
call's media mode selects the application that should handle the call.
An outbound application that deals with voice media modes may want to monitor
the call for silence (a tone) to distinguish who or what is at the called end
of a call. For example, a person at home may answer calls with just a short
"hello." A person in the office may provide a longer greeting, indicating name and
company name. An answering machine may typically have an even longer greeting.
Because media-mode detection enabled by lineMonitorMedia
is implemented as a read-only operation of the call's media stream, it is not
Monitoring of media on a conference call applies only to the hConfCall
, not to the individual participating calls
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