Record laptop webcam and audio, and save to file in mp4 format - modify existing code snippet

I have an existing HTML and .js code snippets that allows the user to select some values from a drop-down list and then to click on a webpage button which then starts the laptop webcam and microphone recording. When the 'stop recording' button is clicked, the video/audio is saved in .webm format. I need this script/code edited so that: - the drop-down values (video resolution etc), are hard-coded into the script as default values - I don't need to change these values - the start recording button does not need to be pressed - the recording starts automatically as soon as the web page is loaded - I will call this webpage from another html page maybe using a form submit tag AND also pass a variable value. (The webpage that calls the recording webpage will have a table of photos on it and each photo will have a unique id reference variable. A photo can be selected by clicking on it, which then calls the recording webpage and passes the unique id value to the recording script). - when the stop recording button is pressed, the video/audio file is automatically downloaded/stored on the laptop as an mp4 file with the unique id value in the filename, and then the html webpage automatically returns to the previous webpage. So basically, the record script runs automatically when the html webpage is opened, and then automatically saves the recorded file and redirects the webpage after the stop recording button is pressed. I can code a little, but I couldn't get the script to run correctly after I removed the drop-down values etc. The html code ([login to view URL]) and js scripts are attached.