C++ BMediaRoster::GetAudioMixer方法代码示例

void
MediaWindow::SelectAudioMixer(const char* title)
{
	media_node mixerNode;
	BMediaRoster* roster = BMediaRoster::Roster();
	roster->GetAudioMixer(&mixerNode);
	fCurrentNode.SetTo(mixerNode);
	_MakeParamView();
	fTitleView->SetLabel(title);
}

void
NodeHarnessWin::MessageReceived(BMessage *msg)
{
    status_t err;

    switch (msg->what)
    {
    case BUTTON_CONNECT:
        mIsConnected = true;

        // set the button states appropriately
        mConnectButton->SetEnabled(false);
        mStartButton->SetEnabled(true);

        // set up the node network
        {
            BMediaRoster* r = BMediaRoster::Roster();

            // connect to the mixer
            err = r->GetAudioMixer(&mConnection.consumer);
            ErrorCheck(err, "unable to get the system mixer");

            // fire off a window with the ToneProducer's controls in it
            BParameterWeb* web;
            r->GetParameterWebFor(mConnection.producer, &web);
            BView* view = BMediaTheme::ViewFor(web);
            BWindow* win = new BWindow(BRect(250, 200, 300, 300), "Controls",
                                       B_TITLED_WINDOW, B_ASYNCHRONOUS_CONTROLS);
            win->AddChild(view);
            win->ResizeTo(view->Bounds().Width(), view->Bounds().Height());
            win->Show();

            // set the producer's time source to be the "default" time source, which
            // the Mixer uses too.
            r->GetTimeSource(&mTimeSource);
            r->SetTimeSourceFor(mConnection.producer.node, mTimeSource.node);

            // got the nodes; now we find the endpoints of the connection
            media_input mixerInput;
            media_output soundOutput;
            int32 count = 1;
            err = r->GetFreeOutputsFor(mConnection.producer, &soundOutput, 1, &count);
            ErrorCheck(err, "unable to get a free output from the producer node");
            count = 1;
            err = r->GetFreeInputsFor(mConnection.consumer, &mixerInput, 1, &count);
            ErrorCheck(err, "unable to get a free input to the mixer");

            // got the endpoints; now we connect it!
            media_format format;
            format.type = B_MEDIA_RAW_AUDIO;
            format.u.raw_audio = media_raw_audio_format::wildcard;
            err = r->Connect(soundOutput.source, mixerInput.destination, &format, &soundOutput, &mixerInput);
            ErrorCheck(err, "unable to connect nodes");

            // the inputs and outputs might have been reassigned during the
            // nodes' negotiation of the Connect().  That's why we wait until
            // after Connect() finishes to save their contents.
            mConnection.format = format;
            mConnection.source = soundOutput.source;
            mConnection.destination = mixerInput.destination;

            // Set an appropriate run mode for the producer
            r->SetRunModeNode(mConnection.producer, BMediaNode::B_INCREASE_LATENCY);
        }
        break;

    case BUTTON_START:
        mStartButton->SetEnabled(false);
        mStopButton->SetEnabled(true);

        // start the producer running
        {
            BMediaRoster* r = BMediaRoster::Roster();
            BTimeSource* ts = r->MakeTimeSourceFor(mConnection.producer);
            if (!ts)
            {
                fprintf(stderr, "* ERROR - MakeTimeSourceFor(producer) returned NULL!\n");
                exit(1);
            }

            // make sure we give the producer enough time to run buffers through
            // the node chain, otherwise it'll start up already late
            bigtime_t latency = 0;
            r->GetLatencyFor(mConnection.producer, &latency);
            r->StartNode(mConnection.producer, ts->Now() + latency);
            ts->Release();
            mIsRunning = true;
        }
        break;

    case BUTTON_STOP:
        StopNodes();
        break;

    default:
        BWindow::MessageReceived(msg);
        break;
    }
}