I need to add audio to an existing mp4 video. You could think of this as background music. There is audio already in the video. But I need to add another audio track, and it needs to be done client side. I'm trying to avoid additional libraries/tech like ffmpeg and wasm. Any thoughts on how to do this with just Javascript and html?
If you just want to add background music to your video, I would recommend editing the video in some video editing software such as imovie or adobe video editior or some online editors because you cannot combine video and audio in HTML or Javascript. Once you are done editing the video, you could save that video and use it in your HTML using the video tag:
<video width="500" height="500" controls>
<source src="the name of your video file goes here" type="video/mp4 or ogg>
</video>