Cannot sending multiple form fields formdata dropzone.js

I'm having a problem sending the images have a text area field for the client to send a description of the photo, and when he sent to the database sends as if all had the same description that was being inserted only one description,

I'm using the library DROPZONE.JS http://dropzonejs.com/

Follow my code .. Help me please.

Dropzone.options.upload = {
    thumbnailWidth: 246,
    thumbnailHeight: 173,
    enqueueForUpload:false,
    paramName: "userfile",
    sending: function(file, xhr, formData) {    
        formData.append("titulo", $("#titulo").val());
        formData.append("evento", <?php echo $this->uri->segment(4); ?>);
        formData.append("capa", $("#cap").val());
    }
};

function upload() {
    var dz = Dropzone.forElement("#upload");
    for (var i = 0; i < dz.files.length; i++) {
        dz.filesQueue.push(dz.files[i]);
    }
    dz.processQueue(); 
}