You can splice video without re-encoding, because video compression eventually has to send a standalone frame (B-frame), so there is a facility to "reset" the c

You can splice video without re-encoding, because video compression eventually has to send a standalone frame (B-frame), so there is a facility to "reset" the current stream without affecting the rest of the video. Both videos need to be the same format, of course, and you need the beginning and end of the host video to be a B-frame (you can insert B-frames cheaply so no issues) and start the spliced clip at a B-frame as well. You can do this with ffmpeg.