[ros-users] ar_pose basic questions

[Bill Morris]

On Fri, 2010-12-03 at 22:49 -0800, Prasad Dixit wrote: 
> Hi, 
> 
> I am trying to run ar_pose node using my webcam logitech pro 9000. I am
> using only single webcam for pattern detection.
> 
> According to the wiki page documentation it subscribes /usb_cam/image_raw
> (sensor_msgs/Image) and
> (/usb_cam/camera_info)
> 
> but when i saw the documentation for "usb_cam bosch drivers" it is
> publishing /usb_cam/image topic. 
> 
> I tried to republish it using republish raw in:=usb_cam/Image
> out:=usb_cam/image_raw from image_transport node, which has got publish but
> ar_pose seems not subscribing/usb_cam/image_raw topic.
> 
> Also, i get continuous stream of messages  like below:
> [swscaler @ 0x87c9be0]No accelerated colorspace conversion found.
> 
> I could not find much about it but saw some conversion related to it in file
> usb_cam_node.cpp line 91 and onwards
> 
>    usb_cam_pixel_format pixel_format;
>     if(pixel_format_name_ == "yuyv")
>       pixel_format = PIXEL_FORMAT_YUYV;
>     else if(pixel_format_name_ == "uyvy")
>       pixel_format = PIXEL_FORMAT_UYVY;
>     else if(pixel_format_name_ == "mjpeg") {
>       pixel_format = PIXEL_FORMAT_MJPEG;
> 
> So, i have questions like,
> 1. How can i publish usb_cam/image_raw topic?
> 2. How can i rid off those warnings/ errors? Is FFMPEG creating some problem
> in my case?
> 3. It is not opening my camera in any viewer in spite of detecting it. I
> tried to open it using brown gscam package and image_viewer which is working
> fine.
> 
> Any help is appreciated.
> 
> Prasad

1) Perhaps at some point in the future we can get all of the
stakeholders to unify the USB camera drivers to make one driver that
works well. You may have better luck with our patched version, or
someone else's patched version.
http://robotics.ccny.cuny.edu/git/usb_cam.git

2) IIRC The color space warning is due to a bug in some version of
libswscaler. YUYV usually works for me.

3) I forget way it don't work, I think it's because its missing
CameraInfo. Try a patched version and see how that goes.

in my mind there should be two webcam drivers for ROS, one for gscam
which uses gstreamer as the infrastructure layer and one driver that
uses UVC/V4L2 that should ship with ROS.