MG 2.1 The upload failed error on media gallery

hi i am admin but
when i going to upload large video file (1.5gb) on MEDIA GALLERY
its show "The upload failed because the file could not be written to the server. The site administrator will need to resolve this
before any files can be uploaded."
my php.ini parameters

PHP post_max_size 3500M
PHP upload_max_filesize 3100M

any help needed