I want to be able to independently set the background content in a single session, and support local image upload as a static background; if the technology is possible, I also want to add the function of MP4 format video as a dynamic background. The video can be played in a loop or mute playback mode. This feature is very helpful in improving the immersion of the RP role-playing chat scene. It is recommended that the transparency and display ratio of the background can also be customized. Would you like me to write a more concise, simplified description for you to use in different scenarios?