When you connect your HD HERO2 camera to an external monitor with an HDMI cable, your camera should automatically go into live-feed mode.  This means that the monitor will display what the camera's image sensor sees.  If your monitor is not displaying the signal, it may not be compatible with the HD HERO2 camera's HDMI output.  Here is a list of the HDMI output settings for the HD HERO2 camera:

 

NTSC HDMI output settings:

WVGA 60fps output: 480p 60fps

WVGA 120fps output: 480p 60fps

720p 30fps output: 720p 60fps

720p 60fps output: 720p 60fps

960p 30fps output: 1080p 30fps

960p 48fps output: 1080p 30fps

1080p 30fps: 1080p 30fps

Setup menu, Photo/video preview outputs: 1080p 30fps

 

 

PAL HDMI output settings:

WVGA 50fps output: 480p 50fps

WVGA 100fps output: 480p 50fps

720p 25fps output: 720p 50fps

720p 50fps output: 720p 50fps

960p 25fps output: 1080p 25fps

960p 50fps output: 1080p 25fps

1080p 25fps: 1080p 25fps

Setup menu, Photo/video preview outputs: 1080p 25fps

 

If your monitor does not support 1080p, the camera will output 1080i 60fps (NTSC) or 1080i 50fps (PAL).  If 1080i60 is not supported, the camera will revert to outputting 720p 60fps (NTSC) or 720p 50fps (PAL).