Scan line only moving in middle 3/4 of the video background

Hi all,

I'm integrating the Vuforia cloud reco api into our app and I'm having a little bit of trouble with the scan line. As the subject states the scan line is only moving in the middle 3/4. Everything else is working fine (recognizing a target is fast anywhere in the camera feed), but this is an annoying UI bug (which is stopping us from deploying).

Is there a common reason for this?

Quick code info:

My renderFrameQCAR is very simple:

// Setting up frame buffer.
glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

QCAR::State state = QCAR::Renderer::getInstance().begin();
QCAR::Renderer::getInstance().drawVideoBackground();

if (QCAR::Renderer::getInstance().getVideoBackgroundConfig().mReflection == QCAR::VIDEO_BACKGROUND_REFLECTION_ON) {
  glFrontFace(GL_CCW);
} else {
  glFrontFace(GL_CW);
}

QCAR::Renderer::getInstance().end();

// Presenting frame buffer

So I don't think this has anything to do with it.

Configure video background is very standard except for one small oddity (makes me think this could contribute): I have to offset the video by 1/4 of the view size, i.e:

config.mPosition = *new QCAR::Vec2I((int)(screenXScaled / 4.0f), (int)(screenYScaled / 4.0f));

Where screenXScaled is the view width multipled by the screen scale.

I'm not sure why this is required, but it seems to be. When I play around with the video size it appears as though the video is centered on a point 1/4 in from the bottom left. i.e. config position = (0, 0) makes the rendered video center on a point 1/4 in from the bottom left. This also means that as the video size grows it starts to grow outside of the opengl rendering view. However, if I apply the above positioning (with viewWidth / 4.0f) it centers in the center of the view and displays correctly (just with the scan line being restricted).

That all being said, that could just be a red herring.

If anyone has ideas as to why this might be happening I'd really appreciate it.

Thanks in advance

- Indigo