It will actually be easier to simply download the video from the other site and upload to yours than it will to try to get their videos to play on your player. Each site has different configurations and different settings and to do that, in a lot of cases, violates the terms of service from the other site (essentially, you are stealing their bandwidth. Normally, other sites will run ads or links back to their site so that after people watch them, they can visit their site, which helps them to pay for the videos that people watch) not to mention that you would spend so much time trying to write code to handle all of the different configurations.