Losing tracking at distances approx > 2 meters (v0.6.6 and v0.7.0)

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Describe the bug
A clear and concise description of what the bug is.
Losing tracking at distances approx > 2 meters (v0.6.6 and v0.7.0)

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error
   Test face tracking at varying distances to the camera (e.g. 1meter, 2meters, 3, meters, 4 meters, etc)
   Recent versions are losing face tracking very often at longer distances.

Expected behavior
A clear and concise description of what you expected to happen.
The symptom is not reproducible on version 0.6.5

Screenshots
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Environment (please complete the following information):

• Operating system version (Windows 10+ Version number): Windows 10
• Webcam model: PS3 Eye
• AITrack version: 0.6.6 and 0.7.0

Additional context
Add any other context about the problem here.
In StandardTracker::proc_face_detect, the rectangle returned in face is enlarged by 0.1x. This works for faces at approximately 1 meter since the face is much larger.
For longer distances (e.g. 2 - 4 meters) the scaling factor needs to be adjusted (e.g. 0.4x for up to 4 meters)

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This symptom is still occurring for version 0.7.1

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A simpler way to fix this may be to use the existing scaling factor 0.1x to enlarge the rectangle.
But the 0.1x number of pixels should not be less than a minumum number of pixels.

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Trying to commit the following to fix this issue but having problems due to conflicts.
This was tested and working for ranges of 4 to 5 meters

void Tracker::proc_face_detect(float* face, float width, float height)
{
float x = face[0];
float y = face[1];
float w = face[2];
float h = face[3];

/* Need to increase boundary by 10% for yaw, pitch and roll but boundary needs a minimum number of pixels for faces at longer distances which are smaller */
int additional_width_margin = (int)(w * 0.1f);
int additional_height_margin = (int)(h * 0.1f);
int minimum_width_margin = (int)width / (4 * 10); 
int minimum_height_margin = (int)height / (4 * 10); 
if (additional_width_margin < minimum_width_margin)
   additional_width_margin = minimum_width_margin;
if (additional_height_margin < minimum_height_margin) 
   additional_height_margin = minimum_height_margin;

int crop_x1 = (int)(x - additional_width_margin);
int crop_y1 = (int)(y - additional_height_margin);
int crop_x2 = (int)(x + w + additional_width_margin);
int crop_y2 = (int)(y + h + additional_height_margin); // force a little taller BB so the chin tends to be covered

face[0] = (float)std::max(0, crop_x1);
face[1] = (float)std::max(0, crop_y1);
face[2] = (float)std::min((int)width, crop_x2);
face[3] = (float)std::min((int)height, crop_y2);

}