OpenAL

I have tried a lot of things, and no matter what I do, alcCaptureOpenDevice() returns NULL. Except when I choose the standard ALSA capture device, but then I get no sound. alGetError and alcGetError both returns AL_NO_ERROR which is quite odd, when it doesn't work.

I hope someone can help me with this, because I'm growing very frustrated.

I'm working on Kubuntu 8.10 using the precompiled openal.

The code works fine on Windows XP with Visual Studio 2005.

Here is the code that I'm using. The initialization is split in two functions. They are called in the order below. The first one opens the output device, and that works fine on both Linux and Windows. The second opens the capture device, and that only works on Windows.

Don't let the Qt code fool you. I have tried using the exact same chars coming from alcGetString(NULL, ALC_CAPTURE_DEVICE_SPECIFIER) as the specifier for the device without any luck.

I have tried running the application under KDE 4 and Fluxbox (to test if a KDE sound service had grabbed the sound card). No difference.

I'm hoping one of you have an idea about something I can do to move on. I'm running out of things to test and debug.

bool OpenALConnector::init() {
	ALDeviceList pDeviceList;
	const int deviceCount = pDeviceList.getNumDevices();
	if (deviceCount == 0) {
		QMessageBox::critical(0, tr("Sound error"), tr("No available sound device"));
		return false;
	}

	ALCdevice *pDevice = 0;
	if (deviceCount == 1) {
		// No need to ask the user
		pDevice = alcOpenDevice(pDeviceList.getDeviceName(0).toAscii().constData());
	} else {
		// More than one to choose from
		QStringList deviceNames;
		for (int i = 0; i < deviceCount; ++i) {
			const QString name(pDeviceList.getDeviceName(i));
			if (i == pDeviceList.getDefaultDevice())
				deviceNames << tr("%1 (default device)").arg(name);
			else
				deviceNames << name;
		}

		bool ok;
		const QString chosenName(QInputDialog::getItem(0, tr("Sound Device..."), tr("Choose sound device"), deviceNames, 0, false, &ok));
		if (!ok || chosenName.isEmpty()) {
			// User cancelled the dialog
			return false;
		} else {
			const int i = deviceNames.indexOf(chosenName);
			if (i < 0)
				// ??? This shouldn't be possible
				return false;

			pDevice = alcOpenDevice(pDeviceList.getDeviceName(i).toAscii().constData());
		}
	}

	if (pDevice == 0) {
		QMessageBox::critical(0, tr("Sound error"), tr("Failed to open sound device"));
		return false;
	}

	ALCcontext* pContext = alcCreateContext(pDevice, 0);
	if (pContext == 0) {
		alcCloseDevice(pDevice);
		QMessageBox::critical(0, tr("Sound error"), tr("Failed to use sound device"));
		return false;
	}

	qDebug("Opened %s device", alcGetString(pDevice, ALC_DEVICE_SPECIFIER));
	alcMakeContextCurrent(pContext);

	// Minor optimization: Don't do 3D spatialization
	alDistanceModel(AL_NONE);

	return true;
}

bool Transmitter::init() {
	ALCcontext* const pContext = alcGetCurrentContext();
	ALCdevice* const pDevice = alcGetContextsDevice(pContext);
	if (alcIsExtensionPresent(pDevice, "ALC_EXT_CAPTURE") == AL_FALSE) {
		QMessageBox::critical(0, "Sound Problem", "Failed to detect Capture Extension\n");
		return false;
	}

	// Get list of available Capture Devices
	const ALchar *pDeviceList = alcGetString(NULL, ALC_CAPTURE_DEVICE_SPECIFIER);
	QStringList devices;
	while (pDeviceList != 0 && *pDeviceList != '\0') {
		devices << pDeviceList;
		pDeviceList += strlen(pDeviceList) + 1;
	}

	// Get the name of the 'default' capture device
	QString defaultCaptureDevice(alcGetString(NULL, ALC_CAPTURE_DEFAULT_DEVICE_SPECIFIER));

	// Choose the output device
	QString device;
	int deviceNo;
	if (devices.count() == 1) {
		// Not much to choose from
		device = devices.at(deviceNo = 0);
	} else {
		QStringList deviceNames;
		foreach (const QString& name, devices) {
			if (name == defaultCaptureDevice)
				deviceNames << tr("%1 (default device)").arg(name);
			else
				deviceNames << name;
		}

		bool ok;
		const QString chosenName(QInputDialog::getItem(0, tr("Sound Device..."), tr("Choose recording device"), deviceNames, 0, false, &ok));
		if (!ok || chosenName.isEmpty()) {
			// User cancelled the dialog
			return false;
		}

		const int i = deviceNames.indexOf(chosenName);
		if (i < 0)
			// ??? This shouldn't be possible
			return false;

		device = devices.at(i);
		qDebug() << "Device chosen:" << device << chosenName;
	}

	// Open the default Capture device to record a 8000Hz 16bit Mono Stream using an internal buffer
	// of mBufferSize Samples (== mBufferSize * 2 bytes)
	mCaptureDevice = alcCaptureOpenDevice(device.toAscii().constData(), mSampleRate, AL_FORMAT_MONO16, mBufferSize);
	ALenum error1 = alGetError(), error2 = alcGetError(mCaptureDevice);
	if (mCaptureDevice == 0 || error1 != AL_NO_ERROR || error2 != AL_NO_ERROR) {
		const QString errorMsg1(alGetString(error1));
		const QString errorMsg2(alGetString(error2));
		QMessageBox::critical(0, "Sound Problem",
							  QString("Failed to open capture device %1\nError message: %2 (%3)\nMessage 2: %4 (%5)")
									  .arg(device).arg(errorMsg1).arg(error1).arg(errorMsg2).arg(error2));
		return false;
	}

	return true;
}

I hope someone can spot something I'm doing wrong here.