Workaround for gphoto2 with certain Sony camera models problem on system restart

For some Sony camera models e.g. the Sony Alpha-A7R III, gphoto2 will not be able to connect and/or trigger an image capture after a Linux computer system restart with the camera powered on. This issue is described in more detail at the gphoto2 github repository https://github.com/gphoto/gphoto2/issues/279 but it is currently unresolved.

gphoto2 will be able to work again with the Sony camera if you physically extract out and plug in the USB cable again. But I wanted to do it programmatically. I found this great utility uhubctl at https://github.com/mvp/uhubctl that I can use with a supported smart USB hub to switch a USB port power off and on. You need to connect the Sony camera to the USB hub, and the hub to a Linux PC, Ubuntu in my case.

In this post, I describe the steps I use to setup and programmatically switch the power to the USB port of the hub connecting to the camera (using a Canon for illustration as I don't have a Sony on hand).

Install uhubctl

1. On the Linux PC, open up a Terminal and install uhubctl.
   
   $ sudo apt install uhubctl
   
   

Identify the USB hub's vendor id and product id

1. In a Terminal, type in the following command:
   
   $ lsusb
   
   A list of usb devices is shown.
   
   
   
   
2. Note down the vendor id and product id of the smart USB hub.
   
   05e3:0610 is identified as the vendor id and product id of the USB hub.
    

Identify the port number of the USB hub that is connected to the camera

1. In a Terminal, type in the following command:
   
   $ sudo uhubctl
   
   A listing of hubs and ports is displayed.
   
   
   
2. First, look for the smart hub with the previously noted vendor id and product id, e.g. 05e3:0610.
    
3. Then under the selected hub, identify the port with the Sony(Canon) camera connected.
   
   Port number 1 is identified.
   
   

Switch off the port to the camera

1. In a Terminal, type in the following command to switch off the USB port of the camera:
   
   $ sudo uhubctl -n 05e3:0610 -p 1 -a 0
   
   where -n 05e3:0610 is the vendor id and product id of the USB hub,
   -p 1 is the port number of the camera
   -a 0 is to power off
   
   
   
   

Switch on the port to the camera

1.  In a Terminal, type in the following command to switch on the port to the camera:
   
   $ sudo uhubctl -n 05e3:0610 -p 1 -a 1
   
   where -n 05e3:0610 is the vendor id and product id of the USB hub
   -p 1 is the port number of the camera
   -a 1 is to power on
   
   
   

Use gphoto2

From this point on, the Sony camera should be functional again from gphoto2.

Setup a Raspberry Pi 4B to publish a webcam with hardware accelerated video encoding

The Raspberry Pi 4B has an integrated video processing unit, a so called GPU. I wanted to use the GPU to offload the video encoding processing from the CPU when I publish my webcam as a RTSP video stream from the Pi board running Ubuntu 20.04 64 bit and using ffmpeg. 

Download and install rtsp-simple-server

1. Using a browser, download and extract the open source rtsp-simple-server from https://github.com/aler9/rtsp-simple-server into a folder, e.g. /path/to/rtsp/
   
   The files rtsp-simple-server and rtsp-simple-server.yml are extracted out.
   
   
2. Open up a Terminal. At the prompt, change directory to the previously created folder /path/to/rtsp/.
   
   $ cd /path/to/rtsp/
   
   
3. Move the binary to the folder /usr/local/bin/
   
   $ sudo mv rtsp-simple-server /usr/local/bin/
   
   
4. Move the yml configuration file to the folder /usr/local/etc/
   
   $ sudo mv rtsp-simple-server.yml /usr/local/etc/
   

Configure rtsp-simple-server to publish the webcam from ffmpeg

1.  Open up a Terminal. At the prompt, change directory to the directory /usr/local/etc/.
   
   $ cd /usr/local/etc
   
   
2. Using a text editor, edit the configuration file rtsp-simple-server.yml. Create a new path name, e.g. cam under the paths key.
   
   

   paths:
     cam:
       runOnDemand: ffmpeg -hide_banner -s 1280x720 -r 25 -i /dev/video0 -b:v 2M -c:v h264_v4l2m2m -f rtsp rtsp://localhost:$RTSP_PORT/$RTSP_PATH
       runOnDemandRestart: yes
   

   
   Notes:
   -s 1280x720 is the source video resolution size from the webcam
   -r 25 is the source sample rate
   -i /dev/video0 is the source webcam video
   -b:v 2M is the output video bit rate
   -c:v h264_v4l2m2m is the video encoder to use
   
   
3. Save and close the configuration file.
   

 Create and start the rtsp-simple-server service

1.  Open up a Terminal. Type in the following to create the systemd service.
   
   

   sudo tee /etc/systemd/system/rtsp-simple-server.service >/dev/null << EOF
   [Unit]
   After=network.target
   [Service]
   ExecStart=/usr/local/bin/rtsp-simple-server /usr/local/etc/rtsp-simple-server.yml
   [Install]
   WantedBy=multi-user.target
   EOF
   

   
   
2. Enable and start the service by executing the following commands. Or reboot the system.
   
   $ sudo systemctl enable rtsp-simple-server
   $ sudo systemctl start rtsp-simple-server
   
   

Viewing the webcam stream using VLC

1. If the configuration parameters are correct, then start up VLC on a PC on the network.
   
   VLC starts up.
   
   
   
2. Select Media | Open Network Stream.
   
   The Open Media dialog box appears.
   
   
   
3. In the URL field, type in the address of the Raspberry Pi e.g. rtsp://192.168.18.5:8554/cam. Then click Play.
   
   If all the parameters are correct, then VLC should show a stream from the webcam.
   
   VLC displaying a webcam stream.
   
   
   Note: if the video stream looks wrong i.e. greenish and weird as shown above, then the ffmpeg version installed on the Raspberry Pi is an older buggy version 4.2.4 and you need to replace it by downloading the latest ffmpeg and building from source.
   

Replacing ffmpeg and build from source

1. Open up a Terminal and remove the system installed ffmpeg with the following command:
   
   $ sudo apt remove ffmpeg
   
   
2. Using a browser and follow the instructions on https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu to install the latest ffmpeg.
   
   
3. Compilation on the Raspberry Pi 4B may take a while, maybe an hour or two so be aware. After compiling successfully, you can try to use VLC and open up the webcam steam again.
   
   VLC displaying the webcam stream correctly.