function [ labels, valid_ids, vid_ids, filenames  ] = extract_BP4D_labels( BP4D_dir, recs, aus )
%EXTRACT_SEMAINE_LABELS Summary of this function goes here
%   Detailed explanation goes here
    
    aus_BP4D = [1, 2, 4, 6, 7, 10, 12, 14, 15, 17, 23];
    
    inds_to_use = [];
    
    for i=1:numel(aus)
    
        inds_to_use = cat(1, inds_to_use, find(aus_BP4D == aus(i)));
        
    end
    num_files = numel(dir([BP4D_dir, '/*.csv']));
    
    labels = cell(num_files, 1);
    valid_ids = cell(num_files, 1);
    vid_ids = zeros(num_files, 2);
    filenames = cell(num_files, 1);
    
    file_id = 1;
    
    for i=1:numel(recs)

        csvs = dir([BP4D_dir, '/', recs{i}, '*.csv']);
    
        for f=1:numel(csvs)
            
            file = [BP4D_dir, '/', csvs(f).name];
            
            [~, filename,~] = fileparts(file);
            filenames{file_id} = filename;
            
            OCC = csvread(file); %import annotations for one video file
            frame_nums = OCC(2:end,1); %get all frame numbers
            codes = OCC(2:end,2:end); %get codes for all action units
            occlusions = OCC(2:end,end);
            
            codes = codes(:, aus_BP4D);
            
            % Finding the invalid regions
            valid = occlusions ~= 1;
            
            for s=1:size(codes,2)
               
                valid = valid & codes(:,s) ~= 9;
                
            end
            
            vid_ids(file_id,:) = [frame_nums(1), frame_nums(end)];

            labels{file_id} = codes(:, inds_to_use);

            % all indices in SEMAINE are valid
            valid_ids{file_id} = valid;
            
            file_id = file_id + 1;
        end 
    end
    
    labels = labels(1:file_id-1);
    valid_ids = valid_ids(1:file_id-1);
    vid_ids = vid_ids(1:file_id-1, :);
    filenames = filenames(1:file_id-1);
    
end