Need better video quality

How do I get better video quality when watching videos on my Meizu M6?
It seems that when ever i download a youtube video thats high quality and then convert it to make it fit the meizu the video has such bad quality , its all jumpy and sometimes hard to watch, if some one could shed some light on this problem it would be great

Thanks swift13

Try Batman converter, it's easy to use and gives you good results.