Portaudio not working with some USB Audio devices - windows

Question

I have a program that outputs audio via Portaudio. It works for the most part, but there are some USB devices that use the built-in Windows USBAudio drivers that don't work.
I don't get any error and the program shows data being processed in my program, but when the audio stream is sent to portaudio, no sound is output from the USB device. It seems as if portaudio is not initializing the device and therefore can't send the data stream to it.
Some USB devices will work on one USB port, but when I move it to a different USB port on the same computer, it will not work.
Other USB devices will not work on any USB port.
However, all the USB devices work fine when outputting sound from other programs or when using the Windows test audio output.
I cannot figure out why some USB devices work and others don;t even though they are all using the same USB drivers.
Here's the part of my code that initiates the portaudio stream:
static int paPlayCallback( const void *inputBuffer, void *output,
unsigned long framesPerBuffer,
const PaStreamCallbackTimeInfo* timeInfo,
PaStreamCallbackFlags statusFlags,
void *userData ){
if(Out2){
int sz= Out2->Size();
if(sz>QUEUE_SIZE)start=1;
if(sz==0){
for(int i=0;i<10;i++)
averagePower[i]= 0.0;
start=0;
}
if(start){
printf("Output queue size %d\n",sz);
while(sampleCount<OUT_BUF_SIZE)
sampleCount+= AddBuffer();
Resample((float*)output, l,r,framesPerBuffer,dev.parameters.channelCount);
DelBuffer();
return paContinue;
}
}
memset(output,0, framesPerBuffer*dev.parameters.channelCount*4);
return paContinue;
}
static void StreamFinished( void* userData )
{
// exit(-1);
}
BOOL Play(int device){
dev.info = Pa_GetDeviceInfo( device );
dev.parameters.device = device;
dev.parameters.channelCount = dev.info->maxOutputChannels;
dev.parameters.sampleFormat = paFloat32;
if((dev.sampleRate = GetSampleRate(&dev.parameters))<=0){
fprintf(stderr,"Error: Bad output device sample rate.\n");
goto error;
}
int frameSize= (int)floor(dev.sampleRate/FPS);
PaError err;
do{
err= Pa_OpenStream(
&dev.stream,
NULL,
&dev.parameters,
dev.sampleRate,
frameSize,
paClipOff,
paPlayCallback,
0);
if(err ){
fprintf(stderr,"Error: Can't open %s in WASAPI exclusive mode.\n",dev.info->name);
}
}while(err != paNoError );
error_check(Pa_SetStreamFinishedCallback( dev.stream, &StreamFinished ));
error_check(Pa_StartStream( dev.stream ));
return TRUE;
error:
return FALSE;
}

Answer 1

It looks like you are opening the steam in shared mode. You must explicitly set the steam to use exclusive mode with the API specific parameters.
This post should demonstrate the correct syntax.
You might verify this by modifying the windows device settings to match your stream settings. If the settings match you should be able to open the device and stream to it successfully.
You may leave the device in shared mode if you query the device to get the default sample rate and type. In shared mode you can only open the device with the default settings.
MSDN article on exclusive streams