Audio get pops with Virtual Audio Cable

Using Cinder
1

Hi all,
I’m trying to feed audio stream from outer apps into Cinder with the help of Virtual Audio Cable (Drivers), kinda counterparts on Windows as Soundflower on Mac.

I started with a simple program, which initializes an audio::InputDeviceNode from the Virtual Audio Device, and directly connect it to a audio::OutputDeviceNode attached to the external speaker. Unfortunately, the output sound has quite a lot pops in it. The Virtual Audio Cable driver seems to be ok, as I tried the same routine in RtAudio with WASAPI, and works fine.

The InputDeviceNode does produce overrun or underrun other than 0 during running time, actually I’ve no idea what’s going on, I just reckon it means the input and output process does not keep up in pace, am I right? I tried the same program on Mac with the exception of using Soundflower, it sounds smooth, and InputDeviceNode::getLastOverrun() / InputDeviceNode::getLastUnderrun() return 0 all the time.

Is there any setting I may ignored in audio context setup?

Thank you!

2

So InputDeviceNode doesn’t produce over / under runs? How about OutputDeviceNode (you can get this by typecasting the Context::getOutuput(). I know, a bit awkward at current), does it produce any xruns?

I’ve got some WASAPI improvements I need to wrap up soon, so hopefully I can test this out as well. I’ve had VB-Audio inputs working in the past but that was a couple years ago now. If you’ve got some specific test code, that would help.

cheers,
Rich

3

Hello Rich,

Thanks for you reply!

The InputDeviceNode in my test program DOES produce over/under runs almost every frame (in main thread).

It seems that OutputDeviceNode does not have the getLastOverrun() or getLastUnderrun() method, I tried the OutputDeviceNode::getLastClip() instead, and get 0 all the way down, which is a good sign according to the documentation.

Here is the minified code

#include "cinder/app/App.h"
#include "cinder/app/RendererGl.h"
#include "cinder/gl/gl.h"
#include "cinder/audio/audio.h"

using namespace ci;
using namespace ci::app;
using namespace std;

class AudioThroughApp : public App {
  public:
	void setup() override;
	void mouseDown( MouseEvent event ) override;
	void update() override;
	void draw() override;

	audio::InputDeviceNodeRef mInput;
	audio::OutputDeviceNodeRef mOutput;
};

void AudioThroughApp::setup()
{
	auto ctx = audio::master();

	audio::DeviceRef inputDevice, outputDevice;

#ifdef _WIN32
	inputDevice = audio::Device::findDeviceByName("CABLE Output (VB-Audio Virtual Cable)");
	if (!inputDevice) {
		console() << "CABLE Output (VB-Audio Virtual Cable) not found" << std::endl;
		::exit(1);
	}

	outputDevice = audio::Device::findDeviceByName("Headphone (Traktor Audio 2 MK2 WDM Audio)");
	if (!outputDevice) {
		console() << "Headphone (Traktor Audio 2 MK2 WDM Audio) not found" << std::endl;
		::exit(1);
	}
#else
	inputDevice = audio::Device::findDeviceByName("Soundflower (2ch)");
	if (!inputDevice) {
		console() << "Soundflower (2ch) not found" << std::endl;
		::exit(1);
	}

	outputDevice = audio::Device::findDeviceByName("Built-in Output");
	if (!outputDevice) {
		console() << "Built-in Output not found" << std::endl;
		::exit(1);
	}
#endif

	mInput = ctx->createInputDeviceNode(inputDevice, audio::Node::Format().channels(2));

	mOutput = ctx->createOutputDeviceNode(outputDevice, audio::Node::Format().channels(2));
	ctx->setOutput(mOutput);

	mInput >> mOutput;

	mInput->enable();
	ctx->enable();
}

void AudioThroughApp::mouseDown( MouseEvent event )
{
}

void AudioThroughApp::update()
{
	console() << "Input: " << mInput->getLastOverrun() << ", " << mInput->getLastUnderrun() << std::endl;
	console() << "Output: " << mOutput->getLastClip() << std::endl;
}

void AudioThroughApp::draw()
{
	gl::clear( Color( 0, 0, 0 ) ); 
}

CINDER_APP( AudioThroughApp, RendererGl )

and sample output in Debug console on Windows 10

Input: 0, 512
Output: 0
Input: 0, 1024
Output: 0
Input: 0, 2048
Output: 0
Input: 2560, 0
Output: 0
Input: 3584, 0
Output: 0

the same program runs smoothly on OSX 10.12, no under/over runs and clips at all.