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VOXL UVC Server

Table of contents

  1. Overview
  2. Installation
  3. Running voxl-uvc-server
  4. Helpful tips
  5. Power issues
  6. Source

Overview

voxl-uvc-server is an application to send video frames from UVC cameras to Modal Pipe Architecture (MPA) pipes. This server is often used in conjunction with voxl-streamer but can be used with any application that desires frames from a UVC camera.

There are a large array of available UVC cameras on the market and it is impossible to say that voxl-uvc-server supports all of them. In general, voxl-uvc-server supports UVC cameras that have raw frame output. It has been specifically tested with:

It has also been tested in conjunction with voxl-streamer using the following viewers on Ubuntu 20.04:

  • QGroundControl v4.1.4
  • QGroundControl v3.5.6
  • VLC 3.0.16

voxl-uvc-streamer will connect with the first UVC camera that is found that meets the specified configuration. It can only support streaming from a single UVC camera at a time. Attempts to launch another instance to stream from a second UVC camera will fail.

Installation

voxl-uvc-server is installed via ipk package. It is currently only available as a dev package.

yocto:/home/root/ipk# voxl-configure-opkg dev
yocto:/home/root/ipk# opkg update
yocto:/home/root/ipk# opkg install voxl-uvc-server

Running voxl-uvc-server

voxl-uvc-server is a command line application and can be started on the command line:

yocto:/home/root# voxl-uvc-server

Use the -h option to view online help:

yocto:/home/root# voxl-uvc-server -h
Usage: voxl-uvc-server <options>
Options:
-d                Show extra debug messages
-m                Show extra MPA debug messages
-v <vendor-id>    USB vendor id of the desired UVC device in hexadecimal (e.g. 090c)
                  Default is search for any vendor id
-p <product-id>   USB product id of the desired UVC device in hexadecimal (e.g. 337b)
                  Default is search for any product id
-r <resolution>   Desired image resolution (e.g. 320x240)
                  Default is 640x480
-f <fps>          Desired frame rate in fps (e.g. 15)
                  Default is 30
-s                Show information about all devices found then exit
-h                Show help

If a camera does not support the default parameters then it can be supported using the correct command line options. Some examples:

  • PureThermal Mini Pro Flir Lepton: voxl-uvc-server -r 160x120 -f 9
  • Flir Boson 640: voxl-uvc-server -r 640x512

Note: The Flir Boson 640 will always run at 60fps even if you request a different rate

Helpful tips

There are a few nice debugging tools available to help trouble shoot issues and / or determine the required configuration for a new camera.

The Linux command line utility lsusb can be very helpful to see what devices are on the USB bus. One can run the command without the USB camera attached, then attach it and see if it appears in the list. This will provide you with the USB vendor and product id of the camera. For example:

yocto:/home/root# lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
yocto:/home/root# lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 002: ID 046d:0825 Logitech, Inc. Webcam C270
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

This shows the Logitech C270 camera with USB vendor id 0x046d and product id 0x0825.

lsusb -v -d <vid:pid> can also provide a lot more information about a specific device. For example:

yocto:/home/root# lsusb -v -d 046d:0825

Bus 001 Device 002: ID 046d:0825 Logitech, Inc. Webcam C270
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          239 Miscellaneous Device
  bDeviceSubClass         2
  bDeviceProtocol         1 Interface Association
  bMaxPacketSize0        64
  idVendor           0x046d Logitech, Inc.
  idProduct          0x0825 Webcam C270
  bcdDevice            0.12
  iManufacturer           0
  iProduct                0
  iSerial                 2 9C06CEC0
  bNumConfigurations      1
... etc. etc. ...

A utility script named show-video-device-info.sh is provided as part of the voxl-uvc-server package. It can also be used to get some useful information about any attached UVC cameras. For example:

yocto:/home/root# show-video-device-info.sh
/dev/video2: UVC Camera (046d:0825) 046d:0825

Running voxl-uvc-server with the -s option will dump some diagnostic information about all of the cameras discovered and then exit.

Running voxl-uvc-server with the -d and / or -v options will cause diagnostic messages to be output as the server is running.

Power issues

Some USB cameras require more power than can be provided by the USB bus and will fail to operate without a separate power source that can provide the needed current. An example of this is the Flir Boson 640. It can operate using a USB 2.0 cable attached to the Voxl adb port, but that is usually not desirable since that port is needed for adb. Attaching it to a USB connector on an add-on board will fail. However, the ModalAI M0078 debug board provides additional power to the USB port and can support the Flir Boson 640.

Source

Source code is here.