function do_3dmouthgt( the_dir )
  
  if nargin < 1
    error( [ mfilename ' needs one input argument.' ] );
  end

  
  d = dir( fullfile( the_dir, 'seq*.mouthgt' ) );

  % Reject file names containing "-interpolated-reprojected"
  
  VIDEO_FRAMERATE = 25;
  
  % To get some information about recordings: use the "seq_av163.m" script.
  CORPUS_PATH = '../..';
  addpath( CORPUS_PATH );

  
  % Loop through input files

  for i_file = 1:length( d )

    considerit = ~d( i_file ).isdir  & ~isempty( strfind( d( i_file ).name, 'cam1' ) ) & isempty( strfind( d( i_file ).name, 'interpolated' ) ) & isempty( strfind( d( i_file ).name, 'reprojected' ) );

    if considerit
      IN_NAME1 = fullfile( the_dir, d( i_file ).name );
      IN_NAME2 = strrep( IN_NAME1, 'cam1', 'cam2' );
      IN_NAME3 = strrep( IN_NAME1, 'cam1', 'cam3' );
      
      if exist( IN_NAME2, 'file' ) & exist( IN_NAME3, 'file' )
	[ p,n,e ] = fileparts( d( i_file ).name );
	ind = strfind( n, 'cam1' );
	seqname = n( 1:ind(1)-2 );
	n = strrep( n, '-cam1', '' );
	
	OUT_NAME3D = fullfile( the_dir, [ p n '.3dmouthgt' ] );
	
	% Files that will contain:
	% - original 2D manual measurements.
	% - between manual measurements: 2D reprojections of the 3D location estimates.
	%
	% The intent is to check visually whether or not the 3D reconstruction worked.
	[ p,n,e ] = fileparts( IN_NAME1 );
	OUT_NAME1 = fullfile( p, [ n '-reprojected' e ] );

	[ p,n,e ] = fileparts( IN_NAME2 );
	OUT_NAME2 = fullfile( p, [ n '-reprojected' e ] );
	
	[ p,n,e ] = fileparts( IN_NAME3 );
	OUT_NAME3 = fullfile( p, [ n '-reprojected' e ] );
	
	disp( ' ' );
	disp( [ 'IN_NAME1:   "' IN_NAME1 '"' ] );
	disp( [ 'IN_NAME2:   "' IN_NAME2 '"' ] );
	disp( [ 'IN_NAME3:   "' IN_NAME3 '"' ] );
	disp( [ 'OUT_NAME3D: "' OUT_NAME3D '"' ] );
	disp( [ 'OUT_NAME1:  "' OUT_NAME1 '"' ] );
	disp( [ 'OUT_NAME2:  "' OUT_NAME2 '"' ] );
	disp( [ 'OUT_NAME3:  "' OUT_NAME3 '"' ] );


	
	% Load
	for a_cam = 1:3
	  cam( a_cam ).mouthgt = load( eval( sprintf( 'IN_NAME%d', a_cam ) ), '-ASCII' );
	end

	%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
	% ( 1 ) Load GT files and details (timecode)
	
	all_timestamps = [];
	
	o = seq_av163( seqname, CORPUS_PATH );
	
	for a = 1:3
	  
	  % Save it as is 
	  
	  cam( a ).mouthgt_orig = cam( a ).mouthgt;
	  
	  % Convert frame # into time stamp
	  
	  cam( a ).mouthgt( :, 1 ) = o.cam( a ).frame1_timestamp + ( cam( a ).mouthgt( :, 1 ) - 1 ) / VIDEO_FRAMERATE;
	  
	  % Make sure the time stamp is unique
	  
	  cam( a ).mouthgt( :, 1 ) = round( cam( a ).mouthgt( :, 1 ) * 1e6 ) * 1e-6;
	  
	  % Keep only manual GT,
	  % discard possible results of previous interpolation
	  
	  cam( a ).mouthgt = cam( a ).mouthgt( find( cam( a ).mouthgt( :, 2 ) == 1 ), : );
	  
	  % Keep only information about a visible mouth!
	  
	  cam( a ).mouthgt = cam( a ).mouthgt( find( cam( a ).mouthgt( :, 3 ) == 1 ), : );
	  
	  % Fix the minor pixel variations in (X,Y) origin between sessions
	  
	  cam( a ).mouthgt( :, 4 ) = cam( a ).mouthgt( :, 4 ) - o.calib.cam( a ).delta_x_from_session08;
	  cam( a ).mouthgt( :, 5 ) = cam( a ).mouthgt( :, 5 ) - o.calib.cam( a ).delta_y_from_session08;
	  
	  % Stack up the list of all timestamps
	  
	  all_timestamps = [ all_timestamps;   cam( a ).mouthgt( :, 1 ) ];
	  
	end
	
	all_timestamps = sort( unique( all_timestamps ) );

	%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
	% ( 2 ) Reconstruct 3D mouth location when possible
	
	% Where we will store the result
	% - column 1: time stamp (in seconds)
	% - column 2: "is_manual" flag (0:interpolated or 1:manual)
	% - column 3 to 5: x,y,z coordinates
	
	mouthgt3d = zeros( 0, 5 );
	
	% Prepare things for "reconstruct_3d"
	for a = 1:3
	  cam( a ).Pmat    = o.calib.cam( a ).session08_Pmat;
	  cam( a ).K       = o.calib.cam( a ).session08_K;
	  cam( a ).kc      = o.calib.cam( a ).session08_kc;
	  cam( a ).alpha_c = o.calib.cam( a ).session08_alpha_c;
	end
	
	% Process data
	
	for t = all_timestamps(:).'
	  
	  % For each timestamp, load corresponding 2D measurements
	  
	  ind_cam = [ NaN NaN NaN ];
	  p2d = repmat( NaN, 3, 3 );
	  
	  for a = 1:3
	    ind = find( cam( a ).mouthgt == t );
	    if length( ind ) == 1
	      ind_cam( a ) = ind;
	      p2d( :, a ) = [ cam( a ).mouthgt( ind_cam( a ), 4:5 ).'; 1 ];
	    end
	  end
	  
	  
	  % binary vector : 0 for unavailable measurement, 1 for available measurement
	  avail = ~isnan( ind_cam );
	  
	  which_avail = find( avail );
	  
	  p3d = [];
	  
	  if all( avail ) | all( avail == [ 1 1 0 ] ) | all( avail == [ 1 0 1 ] )
	    
	    % cams [ 1,2,3 ] or cams [ 1,2 ] or cams [ 1,3 ]
	    % NOT cams [ 2,3 ] because not precise enough in my opinion
	    
	    align_Pmat = eval( [ 'o.calib.rigid' sprintf( '%02d', which_avail ) '_Pmat' ] );
	    p3d = reconstruct_3d( reshape( p2d( :, which_avail ), [], 1 ), cam( which_avail ), align_Pmat );
	    
	    % Store the result
	    % the "1" means that this 3D location estimate
	    % was derived from manual measurements
	    mouthgt3d( end+1, : ) = [ t 1 p3d( 1:3 ).' ];
	    
	    % Sort the matrix by increasing time stamp value
	    [tmp, ind] = sort( mouthgt3d( :, 1 ) );
	    mouthgt3d = mouthgt3d( ind, : );
	    
	    
	  end
	  
	  
	end

	% Save the 3D ground-truth
	
	save_3dmouthgt( OUT_NAME3D, mouthgt3d );
	
	%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
	% ( 3 ) Reprojection on the image plane of each camera
	
	m = mouthgt3d( :, 3:5 ).';
	m( 4,: ) = 1;
	p2d_reproj    = project( m, cam, o.calib.rigid010203_Pmat );
	
	% Put the small pixel deviation (rel. to session08) back in
	for a = 1:3
	  p2d_reproj( 1 + (a-1)*3, : ) = p2d_reproj( 1 + (a-1)*3, : ) + o.calib.cam( a ).delta_x_from_session08;
	  p2d_reproj( 2 + (a-1)*3, : ) = p2d_reproj( 2 + (a-1)*3, : ) + o.calib.cam( a ).delta_y_from_session08;
	end
	
	% Insert the new points in the GT of each camera
	% Save it to a file
	
	t_reproj = mouthgt3d( :, 1 );
	
	for a = 1:3
	  
	  % Translate manual gt back from "timestamp (in seconds)" to "frame number (integer)"
	  cam( a ).mouthgt( :, 1 ) = 1 + round( ( cam( a ).mouthgt( :, 1 ) - o.cam( a ).frame1_timestamp ) * VIDEO_FRAMERATE );
	  
	  % Add the new reprojected 2D measuremenets
	  % (drop old ones in case of conflict)
	  frame_reproj = 1 + round( ( t_reproj - o.cam( a ).frame1_timestamp ) * VIDEO_FRAMERATE );    
	  n = length( frame_reproj );
	  new_mouthgt = [ frame_reproj(:), repmat( [ 0 1 ], n, 1 ), p2d_reproj( (1:2) + (a-1)*3, : ).' ];
	  
	  ind = find( ~ismember( cam( a ).mouthgt_orig( :, 1 ), new_mouthgt( :,1 ) ) );
	  
	  cam( a ).mouthgt = [ cam( a ).mouthgt_orig( ind,: ); new_mouthgt ];
	  
	  % Sort by increasing time index
	  
	  [ tmp, ind ] = sort( cam( a ).mouthgt( :,1 ) );
	  cam( a ).mouthgt = cam( a ).mouthgt( ind, : );
	  
	  % Write out
	  output2d_file = eval( sprintf( 'OUT_NAME%d', a ) );
	  save_mouthgt( output2d_file, cam( a ).mouthgt );
	  
	  % Compute 2D reprojection error
	  %                is_manual & is_visible
	  ind = find( all( cam( a ).mouthgt_orig( :, 2:3 ), 2 ) ); 
	  f = intersect( cam( a ).mouthgt( :,1 ), cam( a ).mouthgt_orig( ind,1 ) );
	  ind_result = find( ismember( cam( a ).mouthgt( :,1 ), f ) );
	  ind_orig   = find( ismember( cam( a ).mouthgt_orig( :,1 ), f ) );
	  delta = cam( a ).mouthgt( ind_result, 4:5 ) - cam( a ).mouthgt_orig( ind_orig, 4:5 );
	  
	  ind = find( delta(:, 1 ) & delta( :,2 ) );
	  repr_error = sqrt( mean( delta( ind,:) .^ 2 ) );
	  disp( sprintf( 'cam%d: 3D->2D reprojection error: [ dx:%6.3f, dy:%6.3f ] pixels', a, repr_error ) );
	  
	  [ tmp, ind_max ] = max( abs( delta( ind, 1 ) ) );
	  f_dx_max   = cam( a ).mouthgt( ind_result( ind( ind_max ) ), 1 );

	  [ tmp, ind_max ] = max( abs( delta( ind, 2 ) ) );
	  f_dy_max   = cam( a ).mouthgt( ind_result( ind( ind_max ) ), 1 );
	  
	  disp( sprintf( '       max dx error on frame #%d,  max dy error on frame #%d', f_dx_max, f_dy_max ) );
	  
	end
	
      end
      
      
    end
    
  end