Only two things could cause this:
Client sideif ng2-file-upload maxFileSize parameter is less than 1MB
Server sideIf you are using PHP on the serverside adjust the following parameters in php.ini
post_max_size = 50M # implies that a single post request should notexceed 50MB at any given time no matter the number of filesuploaded.
upload_max_filesize = 50M # Implies that no individual file shouldexceed 50MB per request
max_file_uploads = 10 # implies that only 10 files can be uploadedin a single request