Question

Background: I’m coding a metro-styled app for Win8. I need to be able to play music-file. Because of quality and space requirements we’re using encoded audio (mp3/ogg).

I’m using XAudio2 to play sound effects (.wav files), but since I couldn’t figure out a way to play encoded audio with it, I decided to play the music files with Media Foundation (IMFMediaPlayer interface).

I downloaded metro apps sample, and found out that the Media Engine Native C++ video playback sample was closest to what I needed.

Now that my app has MediaPlayer playing musics, I ran into a problem. If the device running the app is slow enough, MediaPlayer hangs. When I’m running the release-version of the app on my device, it’s fine and I can hear the music just fine. But when I attach the debugger or run it on a slower device, it hangs when I’m setting bytestream for the MediaPlayer to play.

Here’s some code, you’ll find it pretty similiar to the sample:

StorageFolder^ installedLocation = Windows::ApplicationModel::Package::Current->InstalledLocation;  
m_pickFileTask = Concurrency::task<StorageFile^>(installedLocation->GetFileAsync(filename)), m_tcs.get_token());    
auto player = this;
m_pickFileTask.then([player](StorageFile^ fileHandle)
{
    player->SetURL(fileHandle->Path);
    Concurrency::task<IRandomAccessStream^> fOpenStreamTask = Concurrency::task<IRandomAccessStream^> (fileHandle->OpenAsync(Windows::Storage::FileAccessMode::Read));
    fOpenStreamTask.then([player](IRandomAccessStream^ streamHandle)
        {                               
            MEDIA::ThrowIfFailed(
                    player->m_spMediaEngine->Pause()
                    );
            MEDIA::GetMediaError(player->m_spMediaEngine);

            player->SetBytestream(streamHandle);                        
            if (player->m_spMediaEngine)
            {
                MEDIA::ThrowIfFailed(
                    player->m_spEngineEx->Play()
                    );
                MEDIA::GetMediaError(player->m_spMediaEngine);
            }
        }
    );      
}
);

And here’s the SetBytestream method:

SetBytestream(IRandomAccessStream^ streamHandle)
{
    if(m_spMFByteStream != nullptr)
    {
        m_spMFByteStream->Close();
        m_spMFByteStream = nullptr;
    }

    MEDIA::ThrowIfFailed(
        MFCreateMFByteStreamOnStreamEx((IUnknown*)streamHandle, &m_spMFByteStream)
        );

    MEDIA::ThrowIfFailed(
        m_spEngineEx->SetSourceFromByteStream(m_spMFByteStream.Get(), m_bstrURL)
        );
    MEDIA::GetMediaError(m_spEngineEx); 

    return;
}

The line where it hangs is:

m_spEngineEx->SetSourceFromByteStream(m_spMFByteStream.Get(), m_bstrURL)

When I’m debugging the app, I can press pause and see the stack. Well, not much of it, but atleast I can see it that it’s indefinitely at

ntdll.dll!77b7f4dc()

Any ideas why my app would hang in such a way?

(OPTIONAL: If you know a better way to play mp3/ogg in a c++ metro-styled app, let me know)

Answer 1

Could not figure out why this is happening, but I managed to code a work-a-round:

IMFSourceReader can be used to decode MP3s and feed bytes into XAudio2SourceVoice.

XAudio2 audio stream effect sample contains good example how to do this.