[ros-users] stereo calibration topic requirements?

[Adam Leeper]

Eric,

I am using UVC webcams (Logitech Quickcam Pro for Notebooks) with Morgan
Quigley's uvc_cam driver.

Synchronization may, in fact, be a problem, as I am simply running a
separate instance of uvc_cam for each camera, each publishing to the
appropriate topic but with no synchronization.

As you said, it would be nice to know what is the behavior of the stereo
calibrator (and other image pipeline stereo things) when things aren't well
sync'ed.

--Adam


Can someone
Adam Leeper
Stanford University
aleeper at stanford.edu
719.358.3804


On Tue, Apr 6, 2010 at 5:43 PM, Eric Perko <wisesage5001 at gmail.com> wrote:

> Adam,
>
> So, mine still fails with latest. I did have a thought while looking
> through some of the info published, namely, are your image_raw topics
> synced? I'm trying to use two individual cameras, but because each one
> gets its own camera1394 node, I don't think their timestamps will ever
> really be in sync even with external triggering or some other
> guarantee I can make about the frames themselves matching up. Are you
> running two separate camera driver nodes, or do you actually have a
> stereo camera driver that is outputting synchronized left and right
> images?
>
> What is the behavior of the stereo camera calibrator if the left and
> right image topics are not sycned up? Does it just hang waiting for a
> synchronized pair? If so, it might be really helpful to get some sort
> of warning that the two image topics are out of sync and therefore
> will not be used.
>
> - Eric
>
> On Tue, Apr 6, 2010 at 8:11 PM, Eric Perko <wisesage5001 at gmail.com> wrote:
> > Hey Adam,
> >
> > I'm trying to do stereo calibration as well and running into the exact
> > same problem. I'm switching from boxturtle to latest to see if that
> > will solve the problem. If you do 'rostopic list -v' you will probably
> > see /image listed as being subscribed to, but having unknown type,
> > meaning nothing is publishing it yet. At least that is the behavior I
> > get. However, I was still having the same hanging behavior even after
> > commenting out the line in cameracalibrator.py where it subscribes to
> > /image, so it may or may not be the root problem.
> >
> > My understanding is that when publishing to a /camera_info topic, the
> > timestamps for the camera_info and the image_raw should be synced, so
> > you have to publish at whatever rate you publish your image. I could
> > be wrong, but that is my understanding from the discussion surrounding
> > a previous problem I was having with image_proc not working with
> > camera1394.
> >
> > - Eric
> >
> > On Tue, Apr 6, 2010 at 7:24 PM, Adam Leeper <aleeper at stanford.edu>
> wrote:
> >> Hi all-
> >>
> >> I'm trying to calibrate a pair of cameras for stereo. I only have the
> >> following topics:
> >>
> >>  * /my_stereo/left/image_raw [sensor_msgs/Image] 1 publisher
> >>  * /my_stereo/right/image_raw [sensor_msgs/Image] 1 publisher
> >>
> >> That is, I don't have any topics publishing mono camera info or
> anything.
> >>
> >> I do
> >> rosrun camera_calibration cameracalibrator.py
> >> right:=/my_stereo/right/image_raw left:=/my_stereo/left/image_raw
> >> left_camera:=/my_stereo/left right_camera:=/my_stereo/right
> >>
> >> but it just hangs. Since mono calibration works fine, my only guess is
> that
> >> the stereo routine requires the mono calibration info to proceed, so it
> is
> >> waiting for more topics before continuing. If so, the tutorial should
> >> probably mention that, because right now it just says "check to see that
> >> there is a left and right image_raw topic".
> >>
> >> On a related note, what is the proper way to publish camera info? Do I
> write
> >> a node that just publishes the message every few seconds? It seems that
> the
> >> camera info doesn't change quickly :)
> >>
> >>
> >> Thanks!
> >> --Adam
> >>
> >>
> >>
> >>
> >> Adam Leeper
> >> Stanford University
> >> aleeper at stanford.edu
> >> 719.358.3804
> >>
> >> _______________________________________________
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> >> ros-users at code.ros.org
> >> https://code.ros.org/mailman/listinfo/ros-users
> >>
> >>
> >
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