Hello,
EZSDK demos does not support capturing from USB camera. You need to use other linux apps(mplayer/ffmpeg) over uvcVideo host driver, to capture video from USB camera.
EZSDK demos support capture through component input. Here is some useful links:
http://processors.wiki.ti.com/index.php/TI81XX_PSP_VIDEO_CAPTURE_Driver_User_Guide
Best Regards,
Margarita