Obtaining data from Kinect for specific time

Question

Is there a way to obtain data, such as positioning of a joint, from the Kinect for specific times? I would like to get and save this data for a certain time of my choosing to use for other calculations. Example would be getting the position data of the head at time = 5 seconds after running program and at time = 10 seconds after running program and saving it to a variable.

Error while running: Here is part of the code ....

    void sensor_AllFramesReady(object sender, AllFramesReadyEventArgs e)
    {
        if (closing)
        {
            return;
        }

        //Get a skeleton
        Skeleton first = GetFirstSkeleton(e);

        if (first == null)
        {
            return;
        }

        GetCameraPoint(first, e);

        using (SkeletonFrame skeletonFrame = e.OpenSkeletonFrame())
        {
            if (skeletonFrame == null)
            {
                return;
            }

            this.Recorder.Record(skeletonFrame); // I get an error after the RGB camera view freezes

        }
         // some more stuff 
     }

This is the error message I get:

System.NullReferenceException was unhandled Message=Object reference not set to an instance of an object. Source=SkeletalTracking StackTrace: at SkeletalTracking.MainWindow.sensor_AllFramesReady(Object sender, AllFramesReadyEventArgs e)

Will this.Recorder.Record(skeletonFrame); start the recording or do I need to initialize and declare or call one of the functions to start recording and ask for a name of the file to save to?

Does the replay of the data allow me to pull out specific timestamp values and the data associated at those timestamps?

Answer 1

The Kinect Toolbox offers recording and playback functionality for skeletal data. I am unsure if it supports a "snapshot" mode, where you tell it to take just the current frame, but the code could certainly be adapted to do so.

You can roll your own by setting up the appropriate checks in your SkeletonFrameReady callback. All the skeleton data is available to you in the SkeletonFrameReady callback. You simply need to save the appropriate data to a collection of some type -- you can save every skeleton, or you can set up a timer to check and only capture them ever ??-seconds.

A similar question and answer was addressed here: kinect c# draw and move skeleton from saved data

Something else you could try is to do all the work in a timer:

private void Window_Loaded(object sender, RoutedEventArgs e)
{
    _savedSkeletons = new List<Skeleton>();

    _timer = new DispatcherTimer();
    _timer.Interval = TimeSpan.FromSeconds(5);
    _timer.Tick += (s, o) =>
    {
        using (SkeletonFrame skeletonFrame = KinectSensorManager.KinectSensor.SkeletonStream.OpenNextFrame(15))
        {
            if (skeletonFrame == null || skeletonFrame.SkeletonArrayLength == 0)
                return;

            // resize the skeletons array if needed
            if (_skeletons.Length != skeletonFrame.SkeletonArrayLength)
                _skeletons = new Skeleton[skeletonFrame.SkeletonArrayLength];

            // get the skeleton data
            skeletonFrame.CopySkeletonDataTo(_skeletons);

            foreach (var skeleton in _skeletons)
            {
                if (skeleton.TrackingState != SkeletonTrackingState.Tracked)
                    continue;

                _savedSkeletons.Add(skeleton);
            }
        }
    };

    _timer.Start();
}

The _savedSkeletons variable keeps storing up skeletons every 5 seconds. If you want to save them to a file, you would serialize the data and write it out via a file stream (many examples of how to serialize and output objects out there).

The above code is a simple example and just stores the Skeleton object. To achieve all your goals, you may need to store additional information -- such as a timestamp. You would need to create a custom class to store all the information you want and store those objects.

Remember that the Kinect Toolbox (linked in the first paragraph) already has a recorder. Try it first to see if it will do what you want.

Answer 2

Yes, it is possible, i used the Kinect.Toolbox for this This library have Recorder and Replay class that allow you to Record the frames to the disk and replay the saved frames. I used this library with success, if you want some example code, please let me know.

This discussion are getting bigger, i will edit this to explain some questions

EDIT 1. QUICK TUTORIAL OF KINECT.TOOLBOX

Create 3 buttons in your application (Start Recording, Stop Recording, Start Replay)

Code for your Form.cs

    Stream recordStream;
    KinectRecorder Recorder;
    KinectReplay Replay;

Code for Start Recording Button:

 protected void StartRecord(object sender, RoutedEventArgs e)
    {
        string generatedName = Guid.NewGuid().ToString();
        string recordStreamPathAndName = @"C:\" + generatedName + ".recorded";            
        this.recordStream = File.Create(recordStreamPathAndName);
        this.Recorder = new KinectRecorder(KinectRecordOptions.Color | KinectRecordOptions.Skeletons, recordStream);
    }

Code for Stop Recording button

 if (Recorder != null)
        {
            Recorder.Stop();
            Recorder = null;
        }

Code for Replay Button

try
{
    recordStream = File.OpenRead(this.recordStreamPathAndName);
}
catch (Exception ex)
{
    throw ex;
}

    this.Replay = new KinectReplay(recordStream);
    this.Replay.ColorImageFrameReady += Replay_ColorImageFrameReady;
    this.Replay.SkeletonFrameReady += Replay_SkeletonFrameReady;
    this.Replay.Start();
}

Here we enable the color and skeleton Recorders, now, lets record only the skeleton data, for example porposes. In your SkeletonFrameReady event handler, you need to do something like this

using (SkeletonFrame skeletonFrame = e.OpenSkeletonFrame())
{
    if (skeletonFrame == null)
        return;
        // any other validations...
    this.Recorder.Record(skeletonFrame);
}

Ok, you recorded the frames. Look at the Replay button code, you created a event handler for the ReplaySkeletonFrameReady, remember? (this.Replay.SkeletonFrameReady += Replay_SkeletonFrameReady;)

    void Replay_SkeletonFrameReady(object sender, ReplaySkeletonFrameReadyEventArgs e)
    {
        // do your stuff.
    }

So in your SkeletonFrameReady you will get the recorded skeleton, so, you can get the skeleton and use the saved data.

Answer 3

To wait for x seconds in C# easiest way is

System.Threading.Thread.Sleep(x000);//where x is the time in seconds for which you want app to wait

Example:

System.Threading.Thread.Sleep(4000);//will wait for 4 seconds

Another way is to use timer objects and enable disable them, and read a form static value inside your looping code, check that boolean if something has to be recorded or not