[ros-users] stereo calibration topic requirements?

[Eric Perko]

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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>>
>