VisualGestureBuilder API not working when more than one player - c++

Question

I'm using the VisualGestureBuilder C++ API to track three simple discrete gestures.
When there is only one player in front of the Kinect, it works great.
But as soon as a second player arrives, the gesture analysis seems to go crazy, and for the two players, I get erratic but smooth results, as if the data for the two players and for the three gestures were mixed together, and random data was added...
And while the VGB API is going wrong, I still get valid body data (I'm drawing skeletons at the same time)
I discovered that this phenomenon was triggered as soon as I have more than one IVisualGestureBuilderFrameReader in the not-paused state.
Here are some portions of my code :
class GESTURES_STREAM
{
friend class MY_KINECT;
private:
struct SLOT
{
IVisualGestureBuilderDatabase* database = nullptr;
IGesture** gestures = nullptr;
UINT gestures_count = 0;
IVisualGestureBuilderFrameSource* source = nullptr;
IVisualGestureBuilderFrameReader* reader = nullptr;
IVisualGestureBuilderFrame* frame = nullptr;
};
SLOT slots[BODY_COUNT];
public:
GESTURES_RESULTS gestures_results[BODY_COUNT];
};
GESTURES_STREAM gestures_stream;
//----------------------------------------------------------------------------------------------------
void MY_KINECT::start_gestures_stream(wstring vgb_file)
{
for (int i = 0; i < BODY_COUNT; i++)
{
hr = CreateVisualGestureBuilderDatabaseInstanceFromFile(vgb_file.c_str(), &gestures_stream.slots[i].database);
if (FAILED(hr)) MY_UTILITIES::fatal_error("Erreur initialisation Kinect : gestures");
gestures_stream.slots[i].gestures_count = 0;
hr = gestures_stream.slots[i].database->get_AvailableGesturesCount(&gestures_stream.slots[i].gestures_count);
if (FAILED(hr)) MY_UTILITIES::fatal_error("Erreur initialisation Kinect : gestures");
if (gestures_stream.slots[i].gestures_count == 0)
{
MY_UTILITIES::fatal_error("Erreur initialisation Kinect : gestures");
}
gestures_stream.slots[i].gestures = new IGesture*[gestures_stream.slots[i].gestures_count];
hr = gestures_stream.slots[i].database->get_AvailableGestures(gestures_stream.slots[i].gestures_count, gestures_stream.slots[i].gestures);
if (FAILED(hr)) MY_UTILITIES::fatal_error("Erreur initialisation Kinect : gestures");
/////
hr = CreateVisualGestureBuilderFrameSource(kinect_sensor, 0, &gestures_stream.slots[i].source);
if (FAILED(hr)) MY_UTILITIES::fatal_error("Erreur initialisation Kinect : gestures");
hr = gestures_stream.slots[i].source->AddGestures(gestures_stream.slots[i].gestures_count, gestures_stream.slots[i].gestures);
if (FAILED(hr)) MY_UTILITIES::fatal_error("Erreur initialisation Kinect : gestures");
hr = gestures_stream.slots[i].source->OpenReader(&gestures_stream.slots[i].reader);
if (FAILED(hr)) MY_UTILITIES::fatal_error("Erreur initialisation Kinect : gestures");
hr = gestures_stream.slots[i].reader->put_IsPaused(TRUE);
if (FAILED(hr)) MY_UTILITIES::fatal_error("Erreur initialisation Kinect : gestures");
/////
safe_release(&gestures_stream.slots[i].database);
}
}
//----------------------------------------------------------------------------------------------------
void MY_KINECT::update()
{
//...
//...
// handling all the different stream, including body
//...
//...
if (body_stream.data_is_new == true)
{
for (int i = 0; i < BODY_COUNT; i++)
{
if (gestures_stream.slots[i].source != nullptr)
{
BOOLEAN is_tracked;
if (body_stream.bodies[i]->get_IsTracked(&is_tracked) == S_OK)
{
if (is_tracked == TRUE)
{
UINT64 a;
if (body_stream.bodies[i]->get_TrackingId(&a) == S_OK)
{
UINT64 b;
if (gestures_stream.slots[i].source->get_TrackingId(&b) == S_OK)
{
if (a != b)
{
gestures_stream.slots[i].source->put_TrackingId(a);
}
}
}
BOOLEAN paused;
if (gestures_stream.slots[i].reader->get_IsPaused(&paused) == S_OK)
{
if (paused == TRUE)
{
gestures_stream.slots[i].reader->put_IsPaused(FALSE);
}
}
}
else
{
BOOLEAN paused;
if (gestures_stream.slots[i].reader->get_IsPaused(&paused) == S_OK)
{
if (paused == FALSE)
{
gestures_stream.slots[i].reader->put_IsPaused(TRUE);
}
}
}
}
}
if (gestures_stream.slots[i].reader != nullptr)
{
if (gestures_stream.slots[i].reader->CalculateAndAcquireLatestFrame(&gestures_stream.slots[i].frame) == S_OK)
{
BOOLEAN is_valid;
if (gestures_stream.slots[i].frame->get_IsTrackingIdValid(&is_valid) == S_OK)
{
if (is_valid == TRUE)
{
for (int j = 0; j < gestures_stream.slots[i].gestures_count; j++)
{
wchar_t gesture_name[256];
if (gestures_stream.slots[i].gestures[j]->get_Name(sizeof(gesture_name), gesture_name) == S_OK)
{
IDiscreteGestureResult* discrete_result = nullptr;
if (gestures_stream.slots[i].frame->get_DiscreteGestureResult(gestures_stream.slots[i].gestures[j], &discrete_result) == S_OK)
{
BOOLEAN detected;
if (discrete_result->get_Detected(&detected) == S_OK)
{
if (detected == TRUE)
{
float confidence;
if (discrete_result->get_Confidence(&confidence) == S_OK)
{
gestures_stream.gestures_results[i].results[gesture_name] = confidence;
}
}
else
{
gestures_stream.gestures_results[i].results[gesture_name] = 0;
}
}
safe_release(&discrete_result);
}
}
}
}
}
safe_release(&gestures_stream.slots[i].frame);
}
}
}
}
}
//----------------------------------------------------------------------------------------------------