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c#windowsservicesapitapi

Using TAPI speech in a Windows Service

I have purchased a license of AddTapi.NET to simplify my development using TAPI in a product that runs as a Windows service. I was able to use the TAPI in a Windows GUI and console application and ported the code into my Windows service. At that point, I noted that the code which uses the speech API such as TapiCall.Speak or TapiCall.Play (wavefile) was not generating sound on the phone line and was remaining silent.

There are a couple of previous questions that may relate to my issue.

Question: Playing Voice over a modem from a Windows service indicated a problem using speech that was resolved by spawning a GUI thread in the Windows service. I attempted to do this but was unsuccessful in getting the speech to be heard on the phone.

Question: Access violation with Tapi in Windows service seems to indicate an initial problem with TAPI in a service yet was resolved by using the AddTapi product. The ticket does not explicitly mention the use of the speech API though (SAPI)

I am programming in C# using Visual Studio 2010 and .NET 4.0. I am trying to get this to work on Windows 7. I received an e-mail from AddTapi that indicated that Microsoft changed the security to disallow use of the voice subsystem from services in Win 2008 Server, Windows Vista, and Windows 7. The above articles seem to indicate some success with AddTapi although it may not be on Windows 7.

Given that the main system that I am working with is a Windows service (and child processes), what would seem to be the best approach to getting the speech to work. If I put the SAPI code in a console application, I would like this to be managed without requiring a user to be actively logged onto the computer. There is nothing graphical about my TAPI code. Should I take an approach similar to Article: Launching an interactive process and spawn an interactive process? Have there been any success stories using TAPI speech in a Windows service?

Solution

  • We resolved this problem in AddTapi.NET 5.0. Version 5.0 can use Speech API (TapiCall.Speak and TapiCall.Play) in Windows service applications. There is no need to use a separate process and the service can run under default Local Service account.

    For everyone who doesn't use AddTapi.NET, the key is to use SAPI5 SpVoice object speaking to a custom stream. You cannot instantiate SpAudio or SpMMAudioOut objects in Windows service, so you will need to implement your own stream class and set SpVoice's output to that stream.