I know there are many tutorials on the web on how to chroma key a green screen. But the difference here is that I propose a trick to overcome most cameras' issue: the downsampling of chroma data. This internal downsampling deteriorates the edges between the green screen and your subject, and makes the edges of the footage difficult to key.
With the trick I show you in the video, you can easily overcome this problem.
Check it out and let me know what you think. Hope you will find it useful!