Redirect Audio Output to Audio Input



  • Hello everybody.

    I have the task to redirect Audio Output Signal from USB Audio Interface to Input Audio Signal which i'll be recording and playing with Qt MultiTrack Application. For more information about the my vision of this task see the scheme below.
    !https://lh4.googleusercontent.com/-bZhwO5WVW7I/UpmqSrC-TGI/AAAAAAAAAF4/X9U9aXkJUCA/w923-h694-no/LoopQA.bmp(Scheme)!
    Are there the Qt сlasses which can help me? I tried to use the QAudioRecorder, but it class uses as input device only real input device like Realtek HD Audio Input for example.



  • Well, I guess you would have to write an Audio Driver for your USB device. Or directly access the ring buffer or other kind of memory that your USB device provides inside your Qt application without using the QAudioRecorder?



  • At the moment I'm not having the external USB audio interface (I'm planning buy it). I'm realizing experiments with standard internal sound cards like Realtek or same(I didn't think the sound card name on my home pc).
    I said that I tried to use QAudioRecorder to record output sound from Windows Media Player(it is like the StereoMix mode on Windows OS). For that I had pointed the input device for QAudioRecorder like Realtek Audio Output but it hadn't worked.
    I think there is another method to do it. Vidar, you said something about ring buffer. That is this? Does Qt provide an access to ring buffer?



  • Hi Voronar,
    without special support from your usb device I think that the StereoMix would be the solution. This should be available as Input Device in QT. Did you enable the StereoMix "Device" inside Windows?

    If you want to do more specialized stuff, you will probably directly have to access a lower layer API, such as WASAPI, but then you'd have to use non-QT APIs, such as PortAudio. However, I don't have experiences with those "loopback modes" and cannot say, if they really provide more features than the "Stereo Mix".
    http://msdn.microsoft.com/en-us/library/windows/desktop/dd316551(v=vs.85).aspx



  • Thank you, Vidar. I'll try to enable the "Stereo Mix" on my Windows 7 and then I will see a result. If I don't see wanted result i'll try to use WASAPI or PortAudio.


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