Create openCV VideoCapture from interface name instead of camera numbers

Question

The normal way to create a videocapture is this:

cam = cv2.VideoCapture(n)

where n corresponds to the number of /dev/video0,

Answer 1

If you know the model of the camera, you can look it up in /dev/v4l/by-id/.... We are using an HDMI-USB video converter, and we connect to it like this:

#! /usr/bin/env python
import os
import re
import cv2

DEFAULT_CAMERA_NAME = '/dev/v4l/by-id/usb-AVerMedia_Technologies__Inc._Live_Gamer_Portable_2_Plus_5500114600612-video-index0'

device_num = 0
if os.path.exists(DEFAULT_CAMERA_NAME):
    device_path = os.path.realpath(DEFAULT_CAMERA_NAME)
    device_re = re.compile("\/dev\/video(\d+)")
    info = device_re.match(device_path)
    if info:
        device_num = int(info.group(1))
        print("Using default video capture device on /dev/video" + str(device_num))
cap = cv2.VideoCapture(device_num)

This follows the device name symlink to the /dev/video name, then parses that for the device number.