Time synchronization when using multiple cameras with image_transport

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Hello,

I am using multiple USB cameras for a project and am facing problems with time synchronization. I am currently using image_transport library's subscribeCamera function to subscribe to camera_info and image_rect_color published by image_proc. While one of my cameras is working fine, the second camera is dropping frames due to camera_info being published at a lower rate than the image messages. The following is the warning I am receiving:

    [ WARN] [1467164006.770029982]: [image_transport] Topics '/usb_cam_2/image_rect_color' and '/usb_cam_2/camera_info' do not appear to be synchronized. In the last 10s:
   Image messages received:      120
   CameraInfo messages received: 94
   Synchronized pairs:           6

I have seen a few related answers such as this one link: http://answers.ros.org/question/69925... but in my case one of the cameras is working fine with just subscribeCamera. I was wondering what the reason could be specially for the camera_info being published at a lower rate than the image messages and whether this is something that I can rectify without ApproximateTime message filters as suggested in the answer in the link.

Thanks in advance!