How To Stream and Control Popular DSLR Cameras to your VOXL-based Drone

Table of contents

1. Overview
2. Building voxl-libgphoto2
   1. Installing necessary files
   2. Building Docker Image
3. Hardware Setup
4. Running voxl-libgphoto2
   1. Starting Docker container
   2. Testing gPhoto2 functionality
   3. Streaming video using voxl-libgphoto2
5. Customizing FFmpeg parameters
6. ModalAI Tested Cameras

Overview

voxl-libgphoto2 enables streaming a live video feed from a wide range of digital cameras to QGroundControl. The following software is used to make this possible.

gPhoto2 is a free, redistributable, ready to use set of digital camera software applications for Unix-like systems, supporting more than 2,500 cameras. These cameras include popular options like Sony A6500, Panasonic DC-GH5, Nikon DSC, Nikon CoolPix, Canon PowerShot, and many more!

FFmpeg is a complete, cross-platform solution to stream video. FFmpeg has a large number of options that can be used to tune the video stream to your liking. On top of the default video encoders, voxl-libgphoto2 supports software encoding using libx264 and hardware encoding using OpenMax.

Building voxl-libgphoto2

Installing necessary files

# On host PC
$ git clone git@gitlab.com:voxl-public/voxl-libgphoto2.git

$ cd voxl-libgphoto2

# With VOXL connected to host PC via. ADB
$ ./push-files-to-target

Building Docker Image

# ADB over to VOXL
$ adb shell

# Enable station mode in order to download dependencies
$ voxl-wifi station [ssid] [password]

# Reboot to save changes
$ reboot

After VOXL has rebooted

# ADB over to VOXL
$ adb shell

# Move to Docker directory
$ cd /data/docker

# Build Docker image
$ docker build -t libgphoto2 libgphoto2/

After build has completed, switch WiFi mode to SoftAP

$ voxl-wifi softap [SSID]

# Reboot to save changes
$ reboot

Hardware Setup

In order to stream a video feed to QGroundControl, voxl-libgphoto2 requires the use of a Flight Core or VOXL Flight.

The following additional hardware is required to stream video from a digital camera through VOXL to QGroundControl.

One of the following VOXL Add-on boards is required.

• Before beginning setup, make sure the VOXL is disconnected from both it’s power source and it’s USB to host PC cable

• Attach the add-on board to the VOXL and make sure that the boot switch(es) are turned off or to the left

• Plug the jst side of the MCBL-00009-1 USB Cable into the add-on board

• Plug the camera’s USB cable into both the camera and the USB female side of the MCBL-00009-1 USB cable

• Power the VOXL

Running voxl-libgphoto2

Starting Docker container

Run a container with the following parameters in order to give voxl-libgphoto2 access to the camera via. it’s USB port.

$ adb shell

$ docker run -i -t --rm -v /dev/bus/usb/:/dev/bus/usb --net=host --privileged libgphoto2

Testing gPhoto2 functionality

The gPhoto docs provide a good explanation on how to use the gPhoto command line interface

Here are a few examples:

$ gphoto2 --list-ports
Devices found: 4
Path                             Description
--------------------------------------------------------------
ptpip:                           PTP/IP Connection
ip:                              IP Connection
serial:                          Serial Port Device
usb:001,005                      Universal Serial Bus

In this example we can see that gPhoto has detected a USB bus on the device. However, we cannot tell yet whether we will have write access to the USB device file your camera will be assigned by the operating system.

The next step is to connect your camera and find out whether gPhoto can find it. This only works with USB.

$ gphoto2 --auto-detect
Model                          Port
----------------------------------------------------------
Canon EOS 700D                 usb:001,005

In this case, a camera called “Canon EOS 700D” has been detected on your system’s USB bus.

Next, we can test capturing and image.

$ gphoto2 --capture-image-and-download
New file is in location /capt0000.cr2 on the camera
Saving file as capt0000.cr2
Deleting file /capt0000.cr2 on the camera

This command can be used to take a picture and immediately save the image to the host Docker container instead of the camera.

Streaming video using voxl-libgphoto2

In order to stream a live video feed from the digital camera to QGroundControl, use the following:

$ ./voxl-libgphoto2 192.168.8.XXX

The referenced IP address should be the IP address of the host PC running QGroundControl.

• On the host system, while connected to the VOXL’s WiFi network, run QGroundControl

• In QGroundControl, press the purple QGC logo in the top left corner in order to access the Application Settings menu

• Under the General tab, scroll down until you find the Video section

• Under the Video Source dropdown, choose MPEG-TS (h.264) Video Stream

• In the UDP Port field, enter the default port: 4242

• You will now be able to view the video stream under QGroundControl’s Fly view

Customizing FFmpeg parameters

By default, voxl-libgphoto2 uses the following basic FFmpeg parameters, specified in the voxl-libgphoto2.py script:

$ ffmpeg -i - -c:v libx264 -f mjpeg udp://192.168.8.XXX:4242

These parameters can be modified to change the stream’s encoder, resolution, bitrate, framerate, etc. as needed.

ModalAI Tested Cameras

The following cameras were tested by ModalAI and successfully used to stream video to QGroundControl:

• Canon EOS 700D
• Canon Powershot G7 X Mark III