you can try Free down* v3 standalone video converter script from vidfetch.com . for that you can go to Vidfetch.com and go to the Integration page. Then choose a standalone scripts. You can choose FreeDown v3 ( you can try other two scripts available here as an alternative ) download now option to download the video downloader scripts on your server. Change the permissions of the all the downloaded folders and files to 755. You can then register with vidfetch.com and add your site with url pointing to the script folder web url. Now your should have a functional downloader or converter on your site.
its really easy to use ready made standalone video converter script. Online video converter can be very helpful and it is really easy way to attract traffic.
great that you have tried and also like it. also there are other third party plugins available for integrating the same kind of functionality with various types of scripts and CMS like clip-bucket and wordpress etc.
jwplayer integration is also available at vidfetch.com. Vidfetch.com supports several sites including popular sites.