I'm not happy with my HD video quality. What can I do?

Your HD file is your original file which you uploaded. Whenever it is streamed in HD, it is in the quality you uploaded. We cannot enhance the quality of the uploaded video and at the same time, we cannot reduce it when the HD file is played back. Only non HD files are re-sized through the transcoding process. 

If you desire better video quality, please try to change the export settings/encoding settings for future uploads in your editing software/encoding software.