1. EEC-693/793 Applied Computer Vision with Depth Cameras
Lecture 11
Wenbing Zhao 1

2. Outline Using Kinect’s Microphone Array
Verifying the Kinect audio configuration
The Kinect SDK architecture for audio
How Kinect processes audio signals
Inside Kinect's microphone array
Capturing and playing audio
Processing audio data by suppressing and canceling noise
Understanding sound source localization and beam formation

3. Verifying the Kinect audio configuration
Navigate to Control Panel | Device Manager, look for the Kinect for Windows node, find Kinect for Windows Audio Array Control
Also check Sound, video and game controllers node
Sound driver for microphone array

4. Troubleshooting: Kinect USB Audio not recognizing
While installing the SDK make sure the Kinect device is unplugged
Before using Kinect, restart your system once the installation is done
This will ensure that the skeleton tracking engine tracks only the skeleton
that you have identified and ignores the others.
It's always recommended to assign a dedicated USB Controller to the Kinect sensor

5. Using the Kinect microphone array with your computer
Navigate to Control Panel | Sound and switch to the Recording tab, find Kinect's Microphone Array as a recording device, set it as default
Can test it using Windows sound recorder
This will ensure that the skeleton tracking engine tracks only the skeleton
that you have identified and ignores the others.

6. The Kinect SDK architecture for Audio
Applying smoothing on skeleton data could be very expensive in terms of
application performance. This is because the skeleton stream data itself is massive,
and applying smoothing filtering on it makes data processing slow and this highly
depends on the parameters you are using

7. DirectX Media Object Controls
Noise Suppression (NS)
Acoustic Echo Cancellation (AEC)
Automatic Gain Control (AGC)
SDK exposes a set of Kinect SDK offers APIs to control these above features

8. Major focus area of Kinect audio
Human speech recognition
Recognize player’s voice despite loud noise and echos
Identify the speech within a dynamic range of area
While playing, the player could change his position, or
Multiple players could be speaking from different directions

9. Why Microphone Array?
The logic behind placing microphones in different places is to identify the following:
The direction of the incoming sound
The distance of the sound source => origin of the sound
As all the microphones are placed in different positions, the sound will arrive at each of the microphones at different time intervals

10. Audio signal processing in Kinect
Once the source and position of the sound is calculated, the audio-processing pipeline merges the signals of all microphones and produces a signal with high-quality sound
Kinect can identify the sound within a range of +50 to -50 degrees (NOT radians as stated in the textbook!!!)
KinectAudioSource class
MaxSoundSourceAngle
MinSoundSourceAngle

11. Audio signal processing in Kinect
The SDK fires the SoundSourceAngleChanged event if there is any change in the source angle
The SoundSourceAngleChangedEventArgs class contains two properties:
The current source angle and the confidence that the sound source angle is correct
The sound source angle identifies the direction (not the location) of a sound source
The range of the angle is [-50, +50] degrees
Confidence level
Range: 0.0 (no confidence) to 1.0 (full confidence)
KinectAudioSource class has the SoundSourceAngleConfidence property

12. Beam Forming
Like the cone of light from a lighthouse where the light is the brightest, the audio capture hardware has an imaginary cone that is able to capture audio signals the best
Audio waves that propagate through the length of the cone can be separated from audio waves that travel across the cone
If you point the cone in the direction of the audio that your application is most interested in capturing, you can improve the ability to capture and separate that audio source from other competing audio sources
Use the beam angle to set the direction of the imaginary cone to improve your ability to capture a specific audio source

13. Beam Angle
The beam angle identifies a preferred direction for the sensor to listen
The angle is one of the following values (in degrees): {-50, -40, -30, -20, -10, 0, +10, +20, +30, +40, +50}
The sign determines direction:
A negative number indicates the audio source is on the right side of the sensor (left side of the user)
A positive value indicates the audio source is on the left side of the sensor (right side of the user)
0 indicates the audio source is centered in front of the sensor

14. Sound Source vs. Beam Angle
The sound source angle and the beam angle are both defined from the sensor location. Both angles are defined in the x-z plane of the sensor perpendicular to the z-axis of the sensor. However, the two angles have completely different functionality
The sound source angle identifies the direction (not the location) of a sound source. The range of the angle is [-50, +50] degrees
The beam angle identifies a preferred direction for the sensor to listen. The angle is one of the following values (in degrees): {-50, -40, -30, -20, -10, 0, +10, +20, +30, +40, +50}.

15. Sound Source vs. Beam Angle
Both angles (beam and sound source) are updated continuously once the sensor has started streaming audio data (when the Start method is called)
Use the sound source angle to decide which beam angle to choose if you want to capture a particular sound source

16. Programming Audio Source
Start/stop audio source
The Kinect sensor must be in the running state in order to start the audio stream
If you try to start the audio stream and the sensor is not running, the application will throw an InvalidOperationException
Register sound source angle and beam angle events
Specify audio processing parameters
Manually control beam angle
Recording audio
this.sensor.AudioSource.Start();
this.sensor.AudioSource.Stop();
this.sensor.AudioSource.SoundSourceAngleChanged += soundSourceAngleChanged;
this.sensor.AudioSource.BeamAngleChanged += beamAngleChanged;

17. Setting Audio Processing Parameters
Audio data can be processed by interacting with DMO via KinectAudioSource class
Echo cancellation
CancellationOnly
CancellationAndSuppression
None (default setting)
Noise suppression (enabled by default)
Automatically gain control: amplify weak audio, disabled by default
this.sensor.AudioSource.EchoCancellationMode = EchoCancellationMode.
CancellationOnly;
this.sensor.AudioSource.EchoCancellationSpeakerIndex = 0;
this.sensor.AudioSource.NoiseSuppression = true;
this.sensor.AudioSource.AutomaticGainControlEnabled = true;

18. Beam Angle Mode BeamAngleModel Enumeration
Automatic and Adaptive: Kinect runtime sets the beam angle automatically
Automatic: default setting, use this for a low-volume loudspeaker and/or isotropic background noise
Adaptive: Use this for a high-volume loudspeaker and/or higher noise levels
Manual: The user sets the beam angle to point in the direction of the audio source of interest
The beam angle is located in the xz plane between the z-axis and the direction of an audio source
set the angle using the ManualBeamAngle property
this.sensor.AudioSource.BeamAngleMode = BeamAngleMode.Automatic;
this.sensor.AudioSource.BeamAngleMode = BeamAngleMode.Manual;
// Track the ManualBeamAngle on the right hand position
this.sensor.AudioSource.ManualBeamAngle = Math.Atan(rightHand.Position.X /
rightHand.Position.Z) * (180 / Math.PI);

19. Recording Audio RecordAudio() is blocking public void RecordAudio() {
int recordingLength = (int)10 * 2 * 16000;
byte[] buffer = new byte[1024];
Boolean startAudioStreamHere = false;
using (FileStream fileStream = new FileStream(wavfilename, FileMode.Create)) {
WriteWavHeader(fileStream, recordingLength);
if (audioStream == null) {
startAudioStreamHere = true;
audioStream = this.sensor.AudioSource.Start(); }
int count, totalCount = 0;
while ((count = audioStream.Read(buffer, 0, buffer.Length)) > 0 && totalCount < recordingLength)
fileStream.Write(buffer, 0, count); totalCount += count;
if (startAudioStreamHere == true)
this.sensor.AudioSource.Stop();

20. Recording Audio To avoid blocking the UI, use thread
private void startBtn_Click(object sender, RoutedEventArgs e) {
var audioThread = new Thread(new ThreadStart(RecordAudio));
audioThread.SetApartmentState(ApartmentState.MTA);
audioThread.Start(); }

21. Recording Audio Helper methods
static void WriteWavHeader(Stream stream, int dataLength) {
using (var memStream = new MemoryStream(64)) {
int cbFormat = 18; //sizeof(WAVEFORMATEX)
WAVEFORMATEX format = new WAVEFORMATEX() {
wFormatTag = 1,nChannels = 1,
nSamplesPerSec = 16000, nAvgBytesPerSec = 32000,
nBlockAlign = 2, wBitsPerSample = 16, cbSize = 0 };
using (var binarywriter = new BinaryWriter(memStream))
//RIFF header
WriteString(memStream, "RIFF");
binarywriter.Write(dataLength + cbFormat + 4);
WriteString(memStream, "WAVE");
WriteString(memStream, "fmt ");
binarywriter.Write(cbFormat);
//WAVEFORMATEX
binarywriter.Write(format.wFormatTag);
binarywriter.Write(format.nChannels);
binarywriter.Write(format.nSamplesPerSec);
binarywriter.Write(format.nAvgBytesPerSec);
binarywriter.Write(format.nBlockAlign);
binarywriter.Write(format.wBitsPerSample);
binarywriter.Write(format.cbSize);
//data header
WriteString(memStream, "data");
binarywriter.Write(dataLength);
memStream.WriteTo(stream); }
Recording Audio
Helper methods
struct WAVEFORMATEX {
public ushort wFormatTag;
public ushort nChannels;
public uint nSamplesPerSec;
public uint nAvgBytesPerSec;
public ushort nBlockAlign;
public ushort wBitsPerSample;
public ushort cbSize; }
static void WriteString(Stream stream, string s) {
byte[] bytes = Encoding.ASCII.GetBytes(s);
stream.Write(bytes, 0, bytes.Length); }

22. Build KinectAudio App
Create a new C# WPF project with name KinectAudio
Add Microsoft.Kinect reference
Design GUI
Adding code

23. GUI Design
Image
MediaElement

24. Adding Code Import namespaces Add member variables:
Register WindowLoaded event handler programmatically
using Microsoft.Kinect;
using System.IO;
using System.Threading;
KinectSensor sensor;
WriteableBitmap colorBitmap;
byte[] colorPixels;
// Skeleton[] totalSkeleton = new Skeleton[6];
Stream audioStream;
string wavfilename = "c:\\temp\\kinectAudio.wav";
public MainWindow() {
InitializeComponent();
Loaded += new RoutedEventHandler(WindowLoaded); }

25. Adding Code: WindowLoaded
private void WindowLoaded(object sender, RoutedEventArgs e) {
this.sensor = KinectSensor.KinectSensors[0];
this.sensor.SkeletonStream.Enable();
this.sensor.ColorStream.Enable();
this.sensor.AllFramesReady += allFramesReady;
this.colorPixels = new byte[this.sensor.ColorStream.FramePixelDataLength];
this.colorBitmap = new WriteableBitmap(this.sensor.ColorStream.FrameWidth, this.sensor.ColorStream.FrameHeight, 96.0, 96.0, PixelFormats.Bgr32, null);
this.image1.Source = this.colorBitmap;
this.sensor.AudioSource.SoundSourceAngleChanged += soundSourceAngleChanged;
this.sensor.AudioSource.BeamAngleChanged += beamAngleChanged;
// start the sensor.
this.sensor.Start(); }

26. Adding Code: AudioStream Start/Stop
Stop/start via button clicks
private void startAudioStreamBtn_Click(object sender, RoutedEventArgs e) {
audioStream = this.sensor.AudioSource.Start(); }
private void stopAudioStreamBtn_Click(object sender, RoutedEventArgs e)
this.sensor.AudioSource.Stop();

27. Adding Code: Audio Event Handlers
void beamAngleChanged(object sender, BeamAngleChangedEventArgs e) {
this.soundBeamAngle.Text = e.Angle.ToString(); }
void soundSourceAngleChanged(object sender, SoundSourceAngleChangedEventArgs e)
this.soundSourceAngle.Text = e.Angle.ToString();
this.confidenceLevel.Text = e.ConfidenceLevel.ToString();

28. Adding Code: AllFramesReady Event Handler
void allFramesReady(object sender, AllFramesReadyEventArgs e) {
using (ColorImageFrame imageFrame = e.OpenColorImageFrame())
if (null == imageFrame)
return;
imageFrame.CopyPixelDataTo(colorPixels);
int stride = imageFrame.Width * imageFrame.BytesPerPixel;
this.colorBitmap.WritePixels(
new Int32Rect(0, 0, this.colorBitmap.PixelWidth, this.colorBitmap.PixelHeight),
this.colorPixels,
stride,
0); }

29. Recording/Replay Button Click Events
private void startBtn_Click(object sender, RoutedEventArgs e) {
var audioThread = new Thread(new ThreadStart(RecordAudio));
audioThread.SetApartmentState(ApartmentState.MTA);
audioThread.Start(); }
private void playBtn_Click(object sender, RoutedEventArgs e)
if (!string.IsNullOrEmpty(wavfilename) && File.Exists(wavfilename))
kinectaudioPlayer.Source = new Uri(wavfilename, UriKind.RelativeOrAbsolute);
kinectaudioPlayer.LoadedBehavior = MediaState.Play;
kinectaudioPlayer.UnloadedBehavior = MediaState.Close;

30. Handle Checkbox Events
Must register both checked and unchecked event handlers for each checkbox
private void noiseSuppression_Checked(object sender, RoutedEventArgs e) {
this.sensor.AudioSource.NoiseSuppression = true; }
private void echoCancellation_Checked(object sender, RoutedEventArgs e)
this.sensor.AudioSource.EchoCancellationMode = EchoCancellationMode.CancellationOnly;
this.sensor.AudioSource.EchoCancellationSpeakerIndex = 0;
private void gainControl_Checked(object sender, RoutedEventArgs e)
this.sensor.AudioSource.AutomaticGainControlEnabled = true;

31. Handle Checkbox Events
private void gainControl_Unchecked(object sender, RoutedEventArgs e) {
this.sensor.AudioSource.AutomaticGainControlEnabled = false; }
private void echoCancellation_Unchecked(object sender, RoutedEventArgs e)
this.sensor.AudioSource.EchoCancellationMode = EchoCancellationMode.None;
private void noiseSuppression_Unchecked(object sender, RoutedEventArgs e)
this.sensor.AudioSource.NoiseSuppression = false;

32. EEC492/693/793 - iPhone Application Development
Challenge Tasks
For advanced students, improve the KinectAudio app in the following ways:
Add ProgressBar for recording and replaying
Draw a vertical line in the color image indicating the audio source angle, and another line indicating the beam angle
Manually specify the beam angle to a particular joint, such as the right hand
Observe the sound source angle with the new beam angle
1/2/2019
EEC492/693/793 - iPhone Application Development