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docs/pass.md

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+# HDMI Video Passthrough
+
+This is a new exclusive feature available only on **PiKVM V4 Plus**.
+It allows you to connect PiKVM to the gap between the target host and the display.
+Thus, PiKVM does not interfere with the normal operation of the display and passes
+the video signal through itself until you need remote access via PiKVM
+In this case, PiKVM directs the video stream to the Web UI or VNC.
+
+!!! info
+
+    * The passthrough feature supports a screen resolution **up to 1920x1200** pixels.
+    * Other PiKVM devices besides V4 Plus do not support the passthrough due to hardware limitations.
+
+This is shown more clearly below:
+
+<img src="pass.png" />
+
+-----
+## Setting up the passthrough
+
+1. Connect the display to `OUT2` port on the back side of PiKVM V4 Plus.
+
+2. Update OS and reboot:
+
+    {!_update_os.md!}
+
+4. Switch filesystem to RW-mode:
+
+    ```console
+    # rw
+    ```
+
+3. Add these lines to `/boot/config.txt`:
+
+    ```ini
+    dtoverlay=vc4-kms-v3d
+    disable_overscan=1
+    ```
+
+4. Enable the passthrough service:
+
+    ```console
+    # systemctl enable kvmd-pass
+    ```
+
+5. Perform the soft reboot:
+
+    ```console
+    # reboot
+    ```
+
+After rebooting, you will see an image on the display.
+If you open the stream in the Web UI or VNC, the image on display will be temporarily stopped
+and redirected to the remote access session.
+
+
+-----
+## Current limitations
+
+Please note the feature is still new and will be improved.
+
+* The video cannot be shown simultaneously on the display or in a remote access session.
+    During a remote session, you will see the `STREAM IS ACTIVE` text on the display instad of image.
+
+* Audio is not supported at the moment.