I'm making mp4 (libx264 + aac) videos that have just one static image throughout the whole video. It's basically a narrated text with a nice background.

The question I've is how could I speed up encoding of such videos? Currently the videos are encoding at 50fps which is very, very slow. I can only encode 2000 videos on a single computer in one day.

Any particular settings I could specify to ffmpeg or lib264 library to suggest that there is no motion, and it's just a single image that has to b

For comparison, I was doing .avi (divx + mp3) videos before I moved to mp4, and I was able to encode 6000 - 8000 videos per day.