[ FORMATS of the annotation files ]

Files finishing with ".headgt" contain a 7-column matrix, 
each row is a measurement:

- column 1: integer frame index for this camera.
  Note that this index is camera-dependent, while
  timecodes are not.

- column 2: "is_manual" flag (0 or 1).
  Indicates whether the 2D measurement was provided 
  by a user or by some interpolation/tracking procedure.

- column 3: "is_visible" flag (0, 0.5 or 1).
  Indicates whether the head is visible (1), partially occluded (0.5)
  or not visible at all (0).

- columns 4 to 7: (x_upleft, y_upleft, x_downright, y_downright) 
  pixel coordinates of the head bounding box.

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Files finishing with ".ballgt" contain a 7-column matrix,
with exact same format as ".headgt" files.

Note that the "is_visible = 0.5" flag is generally not used,
since the ball marker is small: we usually simplify by stating
that it is either visible or not.

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Files finishing with ".mouthgt" contain a 5-column matrix, 
each row is a measurement:

- column 1: integer frame index for this camera.
  Note that this index is camera-dependent, while
  timecodes are not.

- column 2: "is_manual" flag (0 or 1).
  Indicates whether the 2D measurement was provided 
  by a user or by some interpolation/tracking procedure.

- column 3: "is_visible" flag (0 or 1).
  Indicates whether the mouth is visible (1) or not (0).

- columns 4 and 5: (x,y) pixel coordinates of the mouth.

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Files finishing with ".3dballgt" or ".3dmouthgt"
contain a 5-column matrix, where each row is a measurement:

- column 1: FLOAT, absolute time value in seconds (NOT a frame index).
  Note that this value is NOT camera-dependent,
  it is basically the time code expressed in seconds.

- column 2: "is_manual" flag (0 or 1).
  Indicates whether ALL 2D measurements used to create
  this 3D location estimate had the "is_manual" flag set to 1.

- column 3 to 5: (X,Y,Z) spatial coordinates in a referent
  of which origin is the middle of the two microphone arrays,
  as shown below:
  
  
                  (window)------------------
  cam1---                   (people)       |
      \                                    |
       \           -----------             |
                             |             |
                   Y         |             |
                   ^         |           (wall)
                  (1)        |             |
                   |         |   (people)  |
                   O ---> X  |             |
                             |             |
                  (2)        |             |
        /                    |             |
       /                     |           (wall)
  cam2<          (table)     |             |
       \                     |    (people) |
        \         \ /        |             |
                   v         |             |
                  cam3       |             |


where (1) and (2) denote locations of the two circular microphone arrays.