• GitHub \- umlaeute/v4l2loopback: v4l2\-loopback device

$ sudo apt install v4l2loopback-utils v4l2loopback-dkms
$ sudo modprobe -v v4l2loopback
insmod /lib/modules/5.4.0-4-amd64/updates/dkms/v4l2loopback.ko 

devices=n を指定することで複数のデバイスが作れる

$ ls -la /dev/video*
crw-rw----+ 1 root video 81, 0 Mar 21 17:31 /dev/video0
crw-rw----+ 1 root video 81, 1 Mar 21 17:31 /dev/video1
$ sudo modprobe -v v4l2loopback devices=3
insmod /lib/modules/5.4.0-4-amd64/updates/dkms/v4l2loopback.ko devices=3
$ ls -la /dev/video*
crw-rw----+ 1 root video 81, 0 Mar 21 17:31 /dev/video0
crw-rw----+ 1 root video 81, 1 Mar 21 17:31 /dev/video1
crw-rw----+ 1 root video 81, 2 Mar 22 22:31 /dev/video2
crw-rw----+ 1 root video 81, 3 Mar 22 22:31 /dev/video3
crw-rw----+ 1 root video 81, 4 Mar 22 22:31 /dev/video4

video_nr=n,n,n... で指定した番号のデバイスを作成できる

$ ls -la /dev/video*
crw-rw----+ 1 root video 81, 0 Mar 21 17:31 /dev/video0
crw-rw----+ 1 root video 81, 1 Mar 21 17:31 /dev/video1
$ sudo modprobe -v v4l2loopback video_nr=3,5,7
insmod /lib/modules/5.4.0-4-amd64/updates/dkms/v4l2loopback.ko video_nr=3,5,7
$ ls -l /dev/video*
crw-rw----+ 1 root video 81, 0 Mar 21 17:31 /dev/video0
crw-rw----+ 1 root video 81, 1 Mar 21 17:31 /dev/video1
crw-rw----+ 1 root video 81, 2 Mar 22 22:33 /dev/video3
crw-rw----+ 1 root video 81, 3 Mar 22 22:33 /dev/video5
crw-rw----+ 1 root video 81, 4 Mar 22 22:33 /dev/video7

card_label="hoge" で名前が付けられる

$ sudo modprobe -v v4l2loopback video_nr=3,4,7 card_label="device number 3","the number four","the last one"
insmod /lib/modules/5.4.0-4-amd64/updates/dkms/v4l2loopback.ko video_nr=3,4,7 card_label="device number 3,the number four,the last one"
$ v4l2-ctl --list-devices
device number 3 (platform:v4l2loopback-000):
        /dev/video3

the number four (platform:v4l2loopback-001):
        /dev/video4

the last one (platform:v4l2loopback-002):
        /dev/video7

Integrated Camera: Integrated C (usb-0000:00:1a.0-1.6):
        /dev/video0
        /dev/video1
        /dev/media0

取り外し

$ sudo modprobe -rv v4l2loopback 
rmmod v4l2loopback

/dev/video9 を作って ffmpeg で動画を流し込む．

$ sudo modprobe -v v4l2loopback video_nr=9
$ ffmpeg -re -i sourcevideo.mp4 -f v4l2 /dev/video9

/dev/video9 を見るとその動画が見える

$ ffplay /dev/video9

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