Key is required, for example if your s3 URL is http://mybucket.s3.amazonaws.com/videos/video.m3u8, the key would be videos/video.m3u8. The video must be a m3u8 file for HLS.
Bucket is required, for example if your s3 URL is http://mybucket.s3.amazonaws.com/videos/video.m3u8, the bucket would be mybucket.
Fallback key is required, for example if your s3 fallback URL is http://mybucket.s3.amazonaws.com/videos/video.mp4, the key would be videos/video.mp4. The video must be an MP4 file. This is used for browsers that do not support HLS.