I saw "https://superuser.com/questions/277642/how-to-merge-audio-and-video-file-in-ffmpeg" and for a project we need to retrieve video stream (RTMP) from a camera and an icecast audiostream and merge them into a video+audio stream. The original camera audio can be ignored. We'll have to make this available for live viewing, so it's crucial there's not too much delay.
Would ffmpeg -i https://path/to/videostream -i https://path/to/audiostream.stream -c:v copy -c:a aac output.mp4 that was suggested in the original thread work?