My objective is take a video that I understand (in my case in Portuguese) and apply an audio effect that transform the conversation in a not understandable language, something similar russian, chinese or arabian, or a totally weird sound. The important is to match the image with the voice. I could reverse the audio, but the image would not match. Is it possible to make something like this?
Demonic speech effect:
- Reverse the audio
- Apply reverb (ensure that reverb tail is not cut off)
- Reverse back again (You may have to realign audio manually)
Try also to change the pitch a few steps down without changing tempo.
Try a tempo alignment / hitpoint detection tool and shuffle the tempo a little to create weird phrase rhythm
You probably should wait with the demonic effect till you applied other tricks, since it will be degraded or make it more difficult for the other effects to work.
I would try effecting and manipulating the original audio in as many different ways as I can (reversing, stretching, granulation, etc.) and then chop them all up and arrange them to match the mouth movements.
This method would be more time consuming than applying a simple effect, but would probably turn out a lot better.