Render an Animation while using the Minim Library

I recently created an audio visualizer with the Minim library. I would now like to render it into mp4. I have tried using saveFrame() to create images of the animation but when I later combine the images into an mp4 file the video does not sync with the audio anymore. I am assuming this is because the saveFrame() function is expensive and can not create the correct amount of images in the time given by the program running. So my question now is how can I render my Processing animation such that when I render it into mp4 the animation matches with audio when I combine the video and audio together in a editing software.