• Connect your VIM4 HDMI Out to an HDMI Display
• Connect your HDMI OUT cable to VIM4 HDMI IN port

You can use gstreamer to capture the HDMI IN frames. Here is en example to capture the HDMI IN frames and encoding them to H264 format and mux to MP4 format store in file /tmp/test71.mp4.

gst-launch-1.0 v4l2src device=/dev/video71 io-mode=dmabuf num-buffers=300 ! video/x-raw,format=NV12,width=1920,height=1080,framerate=30/1,interlace-mode=interleaved ! amlvenc ! h264parse ! qtmux ! filesink location=/tmp/test71.mp4

HDMI input preview can only work under framebuffer console, so you need to use the server image, you can install via OOWOW.

If you use the desktop image, you need to switch to the framebuffer console.

sudo chvt 3

Execute the HDMI Input demo command sudo hdmiin-demo

If everything is OK you will see the HDMI Input source on your display.