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+# UMD Live Patch
+
+This project is a _system module_ for the PlayStation Portable, specifically the [ARK-4] custom firmware.
+
+## Setup
+
+As with any other ARK-4 plugin, place the `umd_livepatch.prx` file in the `SEPLUGINS` directory in your MemoryStick, then enable the plugin for the `VSH` and `UMD` modes.
+
+The `VSH` mode is optional, but will allow you to see the patched game info for your game.
+
+### Patching a game
+
+For performance reasons, this system module does not accept `xdelta3` files you might commonly find. Instead, it uses its own format: UMDiff.
+
+For a given game, copy the `umdiff` file to `/SEPLUGINS/UMDPATCH/` in your MemoryStick, renaming it to match the game ID you want to patch.
+
+For example, a patch for _K-ON! Ho-Kago Live!!_ (game ID `ULJM-05709`) will be saved under `/SEPLUGINS/UMDPATCH/ULJM-05709.UMDIFF`.
+
+> [!WARNING]
+> This plugin **does not** perform integrity checks. It will gleefully "patch"
+> the wrong file if you tell it to, which will probably prevent the game from booting.
+
+### Generating a UMDiff file
+
+This repository contains the `umdiff` tool to generate a UMDiff file.
+
+
+[ARK-4]: https://github.com/psp-archive/ARK-4