C++ Microsoft SAPI: How to set Windows text-to-speech output to a memory buffer?

Question

Hi all,

I have been trying to figure out how to "speak" a text into a memory buffer using Windows SAPI 5.1 but so far no success, even though it seems it should be quite simple.

There is an example of streaming the synthesized speech into a .wav file, but no examples of how to stream it to a memory buffer.

In the end I need to have the synthesized speech in a char* array in 16 kHz 16-bit little-endian PCM format. Currently I create a temp .wav file, redirect speech output there, then read it, but it seems to be a rather stupid solution.

Anyone knows how to do that?

Thanks!

Answer 1

Do you know how to create a memory-mapped file? You could see if the ISpStream will bind to it.

Answer 2

Look at ISpStream::SetBaseStream. Here's a little helper:

inline HRESULT SPCreateStreamOnHGlobal(
                    HGLOBAL hGlobal,            //Memory handle for the stream object
                    BOOL fDeleteOnRelease,      //Whether to free memory when the object is released
                    const WAVEFORMATEX * pwfex, //WaveFormatEx for stream
                    ISpStream ** ppStream)      //Address of variable to receive ISpStream pointer
{
    HRESULT hr;
    IStream * pMemStream;
    *ppStream = NULL;
    hr = ::CreateStreamOnHGlobal(hGlobal, fDeleteOnRelease, &pMemStream);
    if (SUCCEEDED(hr))
    {
        hr = ::CoCreateInstance(CLSID_SpStream, NULL, CLSCTX_ALL, __uuidof(*ppStream), (void **)ppStream);
        if (SUCCEEDED(hr))
        {
            hr = (*ppStream)->SetBaseStream(pMemStream, SPDFID_WaveFormatEx, pwfex);
            if (FAILED(hr))
            {
                (*ppStream)->Release();
                *ppStream = NULL;
            }
        }
        pMemStream->Release();
    }
    return hr;
}