video-latency-test

This project provides software for a simple video latency test, utilizing the Linux framebuffer for video output and OpenCV for camera capture.

Usage

Run video-latency-test from the commandline.

root@raspberrypi4-64:~# video-latency-test -h
usage: video-latency-test [-h] [--frames FRAMES] [--hue HUE] [--csv CSV]
                          output_fb cv2_cap

Run a video latency test

positional arguments:
  output_fb        The name of the framebuffer to use, e.g. fb0
  cv2_cap          Index of the cv2 capture device, e.g. 0

optional arguments:
  -h, --help       show this help message and exit
  --frames FRAMES  Number of frames to capture for the test
  --hue HUE        Hue threshold (uses hue values of 0-180)
  --csv CSV        Location to save a CSV log of captured data

Implementation

The video-latency-test executable accepts a VideoOutputInterface object, and a VideoCapture object, then measures the latency between setting a color on the VideoOutputInterface and detecting that color on the VideoCaptureInterface. The base implementation, using a Linux Framebuffer for the output and a USB camera for the input, is shown in the diagram below.

Video Output

Interface

Framebuffer Implementation

Video Capture

Interface

Framebuffer Implementation

Frame Types

Frame types provide a method of generating frames written to the Video Output device, along with a method of validating those frames from the Video Capture device.

Interface

Solid Colors