App to record, edit and save video

I need a piece of code can edit and save a plain video with pictures and labels on top of the video, the text need to change with simple animations (think about a digital clock counting in one corner of the video) The main issue is performance, for a 70 seconds video the saving time is about 1 minute as well, I need your code to bring down the video saving time to 15 seconds or less. So here is the requirements for the app: 1. take a video in app's temp folder 2. add pictures and texts at certain placers on top of the video 3. the text need to be changed during the video time 4. save the video in 15 seconds (for 70 second video)