Convert mpii annotations from .mat to .json format

mpii_mat2json.m

function mpii_convert_json(  )
% convert mpii annotations .mat file to .json


%% load annotation file
fprintf('Load annotations... ')
data = load('/media/HDD2/Datasets/Human_Pose/mpii/mpii_human_pose_v1_u12_2/mpii_human_pose_v1_u12_1.mat');
fprintf('Done.\n')
%% open file
fprintf('Open file mpii_human_pose_annotations.json\n')
path = '/media/HDD2/Datasets/Human_Pose/mpii/mpii_human_pose_v1_u12_2/';
fileID = fopen(strcat(path, 'mpii_human_pose_annotations.json'),'w');

%% cycle all data and save to file (.json)
fprintf(fileID, '"{');

% annolist
fprintf(fileID, '\\"annolist\\":[');
for i=1:1:size(data.RELEASE.annolist,2)
    fprintf(fileID, '{');
    % image
    fprintf(fileID, '\\"image\\": {');
    fprintf(fileID, '\\"name\\": \\"%s\\"', data.RELEASE.annolist(1,i).image.name);
    fprintf(fileID, '},');
    
    
    % annorect
    fprintf(fileID, '\\"annorect\\": [');
    for j=1:1:size(data.RELEASE.annolist(1,i).annorect,2)
        fprintf(fileID, '{');
        
        flag_comma = 0;
        % x1
        if isfield(data.RELEASE.annolist(1,i).annorect(j),'x1')
             fprintf(fileID, '\\"x1\\": %d', data.RELEASE.annolist(1,i).annorect(j).x1);
             flag_comma = 1;
        end

        % y1
        if isfield(data.RELEASE.annolist(1,i).annorect(j),'y1')
            if flag_comma,  fprintf(fileID, ','); end
            flag_comma = 1;
            fprintf(fileID, '\\"y1\\": %d', data.RELEASE.annolist(1,i).annorect(j).y1);             
        end
        
        % x2
        if isfield(data.RELEASE.annolist(1,i).annorect(j),'x2')
            if flag_comma,  fprintf(fileID, ','); end
            flag_comma = 1;
            fprintf(fileID, '\\"x2\\": %d', data.RELEASE.annolist(1,i).annorect(j).x2);
        end
        
        % y2
        if isfield(data.RELEASE.annolist(1,i).annorect(j),'y2')
            if flag_comma,  fprintf(fileID, ','); end
            flag_comma = 1;
            fprintf(fileID, '\\"y2\\": %d', data.RELEASE.annolist(1,i).annorect(j).y2);
        end
        
        % annopoints
        if isfield(data.RELEASE.annolist(1,i).annorect(j),'annopoints')
            if flag_comma,  fprintf(fileID, ','); end
            flag_comma = 1;
            if isempty(data.RELEASE.annolist(1,i).annorect(j).annopoints)
                fprintf(fileID, '\\"annopoints\\": []');
            else
                %disp(i)
                fprintf(fileID, '\\"annopoints\\": {\\"point\\": [');
                for d=1:1:size(data.RELEASE.annolist(1,i).annorect(j).annopoints.point,2)
                    fprintf(fileID, '{');
                    fprintf(fileID, '\\"x\\": %d, ', data.RELEASE.annolist(1,i).annorect(j).annopoints.point(1,d).x);
                    fprintf(fileID, '\\"y\\": %d, ', data.RELEASE.annolist(1,i).annorect(j).annopoints.point(1,d).y);
                    fprintf(fileID, '\\"id\\": %d ', data.RELEASE.annolist(1,i).annorect(j).annopoints.point(1,d).id);
                    if isfield(data.RELEASE.annolist(1,i).annorect(j).annopoints.point(1,d),'is_visible')
                        fprintf(fileID, ',');
                        if isempty(data.RELEASE.annolist(1,i).annorect(j).annopoints.point(1,d).is_visible)
                            fprintf(fileID, '\\"is_visible\\": []');
                        else
                            fprintf(fileID, '\\"is_visible\\": %d', data.RELEASE.annolist(1,i).annorect(j).annopoints.point(1,d).is_visible);
                        end
                    end
                    fprintf(fileID, '}');

                    if d < size(data.RELEASE.annolist(1,i).annorect(j).annopoints.point,2)
                        fprintf(fileID, ',');
                    end   
                end
                fprintf(fileID, ']}');      
            end
        end
        
        % scale
        if isfield(data.RELEASE.annolist(1,i).annorect(j),'scale')
            if flag_comma,  fprintf(fileID, ','); end
            flag_comma = 1;
            if isempty(data.RELEASE.annolist(1,i).annorect(j).scale)
                fprintf(fileID, '\\"scale\\": []');
            else
                fprintf(fileID, '\\"scale\\": %d', data.RELEASE.annolist(1,i).annorect(j).scale);
            end
        end
        
        % objpos
        if isfield(data.RELEASE.annolist(1,i).annorect(j),'objpos')
            if flag_comma,  fprintf(fileID, ','); end
            flag_comma = 1;
            if isempty(data.RELEASE.annolist(1,i).annorect(j).objpos)
                fprintf(fileID, '\\"objpos\\": []');
            else
                fprintf(fileID, '\\"objpos\\": {');
                fprintf(fileID, '\\"x\\": %d, ', data.RELEASE.annolist(1,i).annorect(j).objpos.x);
                fprintf(fileID, '"y\\": %d', data.RELEASE.annolist(1,i).annorect(j).objpos.y);
                fprintf(fileID, '}');
            end
        end
        
        fprintf(fileID, '}');
        
        if j < size(data.RELEASE.annolist(1,i).annorect,2)
            fprintf(fileID, ',');
        end        
    end
    fprintf(fileID, '],');
    
    
    % frame_sec
    if isempty(data.RELEASE.annolist(1,i).frame_sec)
        fprintf(fileID, '\\"frame_sec\\": [], ');
    else
        fprintf(fileID, '\\"frame_sec\\": %d, ', data.RELEASE.annolist(1,i).frame_sec);
    end

    % vididx
    if isempty(data.RELEASE.annolist(1,i).vididx)
        fprintf(fileID, '\\"vididx\\": [] ');
    else
        fprintf(fileID, '\\"vididx\\": %d ', data.RELEASE.annolist(1,i).vididx);
    end
    
    fprintf(fileID, '}');
    
     if i<size(data.RELEASE.annolist,2) 
        fprintf(fileID, ',');
    end
end
fprintf(fileID, '],');


% img_train
fprintf(fileID, '\\"img_train\\":[');
for i=1:1:size(data.RELEASE.img_train,2)
    fprintf(fileID, '%d', data.RELEASE.img_train(1,i));
    
    if i<size(data.RELEASE.img_train,2) 
        fprintf(fileID, ',');
    end
end
fprintf(fileID, '],');

% version
fprintf(fileID, '\\"version\\": %s,', data.RELEASE.version);

% single_person
fprintf(fileID, '\\"single_person\\":[');
for i=1:1:size(data.RELEASE.single_person,1)
    if isempty( data.RELEASE.single_person{i,1})
         fprintf(fileID, '[]');
    elseif size( data.RELEASE.single_person{i,1},1) == 1
        fprintf(fileID, '%d', data.RELEASE.single_person{i,1});
    else
        fprintf(fileID, '[');
        for j=1:1:size( data.RELEASE.single_person{i,1},1)
            fprintf(fileID, '%d', data.RELEASE.single_person{i,1}(j));
            if j < size( data.RELEASE.single_person{i,1},1)
                fprintf(fileID, ',');
            end
        end
        fprintf(fileID, ']');
    end
    
    if i<size(data.RELEASE.single_person,1) 
        fprintf(fileID, ',');
    end
end
fprintf(fileID, '],');

% act
fprintf(fileID, '\\"act\\":[');
for i=1:1:size(data.RELEASE.act,1)
    fprintf(fileID, '{');
    % cat_name
    if isempty(data.RELEASE.act(i,1).cat_name)
        fprintf(fileID, '\\"cat_name\\": [], ');
    else
        fprintf(fileID, '\\"cat_name\\": \\"%s\\", ', data.RELEASE.act(i,1).cat_name);
    end
    
    % act_name
    if isempty(data.RELEASE.act(i,1).act_name)
        fprintf(fileID, '\\"act_name\\": [], ');
    else
        fprintf(fileID, '\\"act_name\\": \\"%s\\", ', data.RELEASE.act(i,1).act_name);
    end
    
    % act_id
    fprintf(fileID, '\\"act_id\\": %d', data.RELEASE.act(i,1).act_id);
    
    fprintf(fileID, '}');
    
    if i<size(data.RELEASE.act,1) 
        fprintf(fileID, ',');
    end
end
fprintf(fileID, '],');

% video_list
fprintf(fileID, '\\"video_list\\":[');
for i=1:1:size(data.RELEASE.video_list,2)
    fprintf(fileID, '\\"%s\\"', data.RELEASE.video_list{1,i});
    
    if i<size(data.RELEASE.video_list,2) 
        fprintf(fileID, ',');
    end
end
fprintf(fileID, ']');

%% close file
fprintf(fileID, '}');
fclose(fileID);

fprintf('Script complete.\n')
end

JSONDecodeError: Extra data: im getting this error when Im trying to read the file

It's been a while but do you remember finding any solution to this?