Faster way to get stereo images at 640x480 from Raspberry pi

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Hello All,

I have connected 2 logitech C930e web cameras to a Raspberry Pi3 running a Ubuntu Mate and ROS Kinetic. I want to process the images on my laptop and only remotely see what the Pi sees using ROS.

Using uvc_camera package and some tweaks, I am able to publish 320x240 grayscale stereo frames at about 5fps.

Output of rostopic delay is as follows,

average: 221.12KB/s
    mean: 76.85KB min: 76.85KB max: 76.85KB window: 36
average: 221.80KB/s
    mean: 76.85KB min: 76.85KB max: 76.85KB window: 39

From iftop i can see that for 2s the used bandwidth is 3.65Mb.

Could anyone help me as to how i can increase the speed of the transfer. ? I want to be able to work at atleast 15fps.

Also is it possible to run a live video stream using gstreamer or flask and then publish it to ros from the host system. ?

Thank you !