HAP Codec is a collection of high-performance codecs optimized for high-resolution video playback that runs on the GPU, substantially reducing CPU usage for media playback. It has become the standard for high-performance, high-resolution movie playback. Reality 4.26 editor has HAP codec plugin which must be enabled to be able to use this codec using GPU accelerated encoding.
HAP Media plugin will be set to Enabled by default in Reality editor.
Open your Project in the Reality Editor.
From the main menu in the Unreal Editor, select Edit > Plugins.
Under the Media Player category, find the HAP Media Plugin and check its Enabled box.
In case HAP Media plugin was not pre-enabled, after enabling, click Restart Now as prompted to restart your Project and apply the change.