How to organize the upload of audio recordings with conversion?

Question

MP3

Almost every day there are audio recordings 50 min = mp3 45 mb. I want to upload them online after converting them into a format that is more convenient for broadcasting.
I need hosting and conversion. Large disk VDS solutions come to mind. However, VDS, whose processor is needed once a day for 5 minutes, is unprofitable to use for conversion.
I think it's more logical to convert on the client, perhaps through a browser plugin. The difficulty is that you need to simplify the task as much as possible for the user who uploads the file. It should not float anything at all. He just pours.