Speech Input Events

In addition, to the Command event notification, Agent also notifies the input-active client when the server turns the Listening mode on or off, using the ListenStart and ListenComplete events (IAgentNotifySinkEx::ListeningState). However, if the user presses the Listening mode key and there is no matching speech recognition engine available for the topmost character of the input-active client, the server starts the Listening hotkey mode time-out, but does not generate a ListenStart event for the active client of the character. If, before the time-out completes, the user activates another character with speech recognition engine support, the server attempts to activate speech input and generates the ListenStart event.

Similarly, if a client attempts to turn on the Listening mode using the Listen method and there is no matching speech recognition engine available, the call fails and the server does not generate a ListenStart event. In the Microsoft Agent control, the Listen method returns False, but the call does not raise an error.

When the Listening key mode is on and the user switches to a character that uses a different speech recognition engine, the server switches to and activates that engine and triggers a ListenComplete and then a ListenStart event. If the activated character does not have an available speech recognition engine (because one is not installed or none match the activated character's language ID setting), the server will trigger the ListenComplete event for the previously activated character and passes back a value in the Cause parameter. However, the server does not generate ListenStart or ListenComplete events for the clients that do not have speech recognition support.

If a client successfully calls the Listen method and a character without speech recognition engine support becomes input-active before the Listening mode time-out completes, and then the user switches back to the character of the original client, the server will generate a ListenStart event for that client.

If the input-active client switches speech recognition engines by changing SRModeID while in Listening mode, the server switches to and activates that engine without re-triggering the ListenStart event. However, if the specified engine is not available, the call fails (raises an error in the control) and the server also calls the ListenComplete event.