Drops first second worth of frames

Some of the initial timestamps incoming from the camera driver have a
weird timestamp (e.g., negative).
We now drop the first second worth of frames and consider from that on
that the driver is stable.

At that time, we synchronize the recording started time to correspond to
the driver timestamp 0 as well as the global timer to correspond to the
current timestamp.

src/ImageAcquisition.cpp

@@ -185,6 +185,8 @@ ImageAcquisition::ImageAcquisition(QObject *parent) : QObject(parent),
     if (master) {
         qDebug() << "Master is " << camToStr(*master);
 
+        dropCountWhenStarting = master->format.fps; // drop first second worth of frames
+
         // support frame callback does not work properly so we test the callback ourselves
         // if( videoManControl.supportFrameCallback(master->id) )
         //videoManControl.setFrameCallback(master->id, &ImageAcquisition::frameCallback, this);
@@ -231,11 +233,22 @@ void ImageAcquisition::frameCallback(char *pixelBuffer, size_t input, double tim
 
 void ImageAcquisition::frameCallbackInternal(char *pixelBuffer, size_t input, double timestamp)
 {
-    if (!ready) {
-        recordingStarted = GetTickCount64();
-        gTimer.setOffset(recordingStarted+1e3*timestamp);
+    static double initial;
+
+    if (!ready)
+        ready = true;
+
+    if ( dropCountWhenStarting == 0) {
+        recordingStarted = GetTickCount64() - 1e3*timestamp; // i.e., when the camera timestamp was 0
+        gTimer.setOffset(recordingStarted + 1e3*timestamp); // synchronize timer with current timestamp
+        initial = 1e3*timestamp;
+    }
+
+    if (dropCountWhenStarting >= 0) {
+        dropCountWhenStarting--;
+        videoManControl.releaseFrame( master->id );
+        return;
     }
-    ready = true;
 
     if (running && pixelBuffer != NULL) {
         JournalEntry entry(recordingStarted+timestamp*1e3);

src/ImageAcquisition.h

@@ -56,6 +56,7 @@ public:
     Mat latestSlaveFrame;
     Camera *slave;
     bool running;
+    int dropCountWhenStarting;
 
 signals:
     void imageAcquisitionDone(JournalEntry journalEntry);