Miscellaneous Topics

Raspberry Pi

Fisheye USB Camera on Raspberry Pi

• The team says it would be cool to stream video from the robot back to the drivestation
• To offload the Roborio, use a Raspberry Pi to interface the FishEye Camera

First Steps

The page below documents some exploratory steps to display video from a 180-degree FishEye USB Camera

• Ensure the following tools are installed on the RaspBerry Pi

 ffmpeg
 ffplay
 v4l2-ctl

Use command: which <tool>, where <tool> is one of the tools from list above

• If not already present, install:

 sudo apt install ffmpeg ffplay v4l2

• Ensure the FishEye camera is connected to the Raspberry Pi
• Show all available Video Cameras

 v4l2-ctl --list-devices

Camera should show as /dev/video0 or /dev/video1. Determine which device it is by running this command if necessary:

 dmesg

• Examples below assume that the device is /dev/video1.
• To show video formats that the camera supports:

 ffmpeg -f v4l2 -list_formats all -i /dev/video1

• To record to a file "output.mp4" using USB Camera device "/dev/video1".
• The example below uses the highest resolution that the FishEye Camera was found to support: 1920x1080 (HD resolution)

 ffmpeg -f v4l2 -framerate 25 -video_size 1920x1080 -i /dev/video1 output.mp4

• Play the recorded file

 ffplay ./output.mp4

• To display the camera's video directly without recording

 ffplay -f v4l2 -framerate 25 -video_size 1920x1080 -i /dev/video1

Online reference for above

• Using a USB Camera with ffplay/ffmpeg tools: https://trac.ffmpeg.org/wiki/Capture/Webcam

Next Steps

The steps documented above record to or play locally on the Raspberry Pi.
We need to take this to the next level and stream to a different PC, possibly the drive-station if that is legal.

• Use ffmpeg to record from Fisheye camera to a local video file using MPEG2 or MPEG4 compression
• Stream the above compressed video from Raspberry Pi to a network-connected PC (Windows preferably). Tools to explore:

  ffplay or ffmpeg
  FFPlay/FFmpeg Documentation

• Pre-requisite for above: explore Windows or Linux players that can handle the video stream.
• Explore doing the same streaming as above using UDP if not already used in streaming step above. UDP would be probably better for the environment that prevails at game venues.
• Fine tune using different video formats, bitrates. See suggested reading section below.

Suggested reading

Below we suggest a few initial resources to get you started, but do your own research as well

• Learn about:

Video

• Video File formats:
• Video bitrates

Some networking concepts

• Overview of networking
• Networking data rate and bandwidths
• Packets in networking
• Network Congestion
• Network Transports

Learn the difference between connection-oriented and datagram-oriented protocols

• Difference between TCP (connection-oriented) and UDP(datagram)