I have a video Video1.mkv with audio and video stream. I have 3 other videos V1.mp4, V2.mp4 and V3.mp4 without audio. I would like to keep the audio stream from Video1.mkv and replace the beginning of Video1.mkv with the concatenated V1.mp4+V2.mp4+V3.mp4
Is there a way to do this without re-encoding? Also, Video1 is 23.98fps and the other streams are 24fps. Is that a problem?
For reference I saw this question was asked before - Replace parts of video with another video with ffmpeg
But the answer was about replacing the video with a black screen.