From the HD621 Manual:
Quote
HDMI Output: Video – This outputs the video information present on the selected HDMI input. By default, it does not carry the audio information, but can be configured to do so.

808v6, M60, MC200, HD621, Lumagen XE, 504, SB Touch, 563, 201, 204, 208, MPMAX 221, M80, Explorer, Explorer2.