libomap3cam or omap3camd (I think) handles autoexposure. I tried your modified dsp driver for recording at HD. (Had to modify gdigicam-camerabin.c in package libgdigicam-gst-camerabin0) But it can not create the gstreamer-pipeline anymore. I don't know why.
gst-launch-0.10 -v -m camerabin videosrc=v4l2camsrc videopp=dspvpp audioenc=nokiaaacenc filename=test720p_audio.mp4 mode=1 videoenc=dspmp4venc videomux=ffmux_mp4 video-capture-width=1280 video-capture-height=720