I'm using the GF video-capture API to display video on an ADS5121.  At the end of "Using the Video-Capture API" (http://
cvs.qnx.com/developers/docs/6.4.0/gf/dev_guide/vidcap.html) it says:

"At this point the video-capture device is started, and it's sending video to the layer we bound to it. You can now 
adjust the appearance of the video by: 
...
- cropping the captured video by using gf_vcap_set_input_viewport() "


I can call gf_vcap_set_input_viewport() during initial video setup then it works fine and the video is cropped as 
desired.  If I try to call gf_vcap_set_input_viewport() after the video has been running for awhile then the call seems 
to have no effect.  I am calling gf_vcap_update() after the the call to set input viewport.  I also verified that both 
GF_LAYER_CAP_PAN_SOURCE and GF_LAYER_CAP_PAN_DEST are enabled by calling gf_layer_query.

I need to be able to dynamically crop the incoming video.  Any thoughts?  Do I need to disable and then enable video 
capture or the layer the video is being displayed on?  If it matters, the video is being displayed on the main layer.

Thanks.