$ v4l2-ctl -D --all -d /dev/video7
Driver Info:
  Driver name      : v4l2 loopback
  Card type        : V4L2 Loopback
  Bus info         : platform:v4l2loopback-000
  Driver version   : 5.4.78
  Capabilities     : 0x85208002
    Video Output
    Video Memory-to-Memory
    Read/Write
    Streaming
    Extended Pix Format
    Device Capabilities
  Device Caps      : 0x05208002
    Video Output
    Video Memory-to-Memory
    Read/Write
    Streaming
    Extended Pix Format
Priority: 0
Video output: 0 (loopback in)
Format Video Output:
  Width/Height      : 0/0
  Pixel Format      : 'BGR4' (32-bit BGRA/X 8-8-8-8)
  Field             : None
  Bytes per Line    : 0
  Size Image        : 0
  Colorspace        : sRGB
  Transfer Function : Default (maps to sRGB)
  YCbCr/HSV Encoding: Default (maps to ITU-R 601)
  Quantization      : Default (maps to Full Range)
  Flags             : 
Streaming Parameters Video Capture:
  Frames per second: 30.000 (30/1)
  Read buffers     : 8
Streaming Parameters Video Output:
  Frames per second: 30.000 (30/1)
  Write buffers    : 8

User Controls

                    keep_format 0x0098f900 (bool)   : default=0 value=0
              sustain_framerate 0x0098f901 (bool)   : default=0 value=0
                        timeout 0x0098f902 (int)    : min=0 max=100000 step=1 default=0 value=0
               timeout_image_io 0x0098f903 (bool)   : default=0 value=0
$ ls /usr/lib/x86_64-linux-gnu/obs-plugins/
decklink-ouput-ui.so
frontend-tools.so
image-source.so
linux-alsa.so
linux-capture.so
linux-decklink.so
linux-jack.so
linux-pulseaudio.so
linux-v4l2.so
obs-ffmpeg
obs-ffmpeg.so
obs-filters.so
obs-outputs.so
obs-transitions.so
obs-x264.so
rtmp-services.so
text-freetype2.so
vlc-video.so

<embed src="animation.gif" type="image/gif" autoplay controls loop=true muted=true />
<embed src="photo.jpg" type="image/jpeg" muted=true />
<embed src="bgm.ogg" type="audio/ogg" controls loop=true novideo=true />