# stereo and tracking camera voxl_cam_ros

Source: https://forum.modalai.com/topic/363/stereo-and-tracking-camera-voxl_cam_ros
Category: VOXL SDK and Software (https://forum.modalai.com/category/47/voxl-sdk-and-software)
Posted: 2021-07-28 19:53:19 UTC by rapit
Replies: 3 · Views: 1083

## rapit · 2021-07-28 19:53:19 UTC

Hi,
I am trying to publish some stereo output from the flight deck via ros with running `voxl_vision_px4` in the background. 
As stated in your docs I tried `yocto:~# roslaunch voxl_cam_ros stereo.launch is_cam_master:=false` but the launch always fails. 

```
ERROR: The requested frame_id(0) does not exist in the queue.
[ERROR] [1627501325.921901556]: GetImageData() Unable to get Frame data for id: 0 rc: -2
[stereo/stereo_nodelet_manager-2] process has died [pid 5056, exit code -11, cmd /opt/ros/indigo/lib/nodelet/nodelet manager __name:=stereo_nodelet_manager __log:=/home/root/.ros/log/e264a974-efdb-11eb-b918-d80f995591f7/stereo-stereo_nodelet_manager-2.log].
```

I think my id's are correct, if I stop `voxl-vision-px4.service` and set `is_cam_master` to `true` it works. It also works if I choose the `stereo_merged.launch` launchfile, even with voxl-vision-px4 in the background. Other combinations (hires, tracking) work as well so I am wondering if there is a technical limitation on this specific combination or is this supposed to work. I am still on version 2.3 as I need the Apriltag support.

Thanks!

## Reply by Guest · 2021-07-28 20:56:52 UTC

Hi rapit,

Our current stable SDK (voxl-suite 0.4.6) has apriltag support through [voxl-tag-detector](https://gitlab.com/voxl-public/modal-pipe-architecture/voxl-tag-detector), I'd recommend upgrading to the latest software as that's what we've been running with here in the lab and will be more familiar with issues that arise.

## Reply by rapit · 2021-07-29 09:16:44 UTC

Good news, I didn't know that Apriltags are already supported, maybe the docs should be updated.
I updated and all streams are working simultaneously in the new architecture. Thanks.

## Reply by Guest · 2021-07-29 16:56:45 UTC

Glad to hear it's working!

Yes, We're days away from finishing a rework of our docs that includes all the information about the new architecture, should be seeing it real soon.