Preview video in Android app

Question

I am creating a video editing application and currently I use ffmpeg for the encoding and decoding process (my application can easily perform tasks where real-time preview is not required, for example, reverse video or apply filters like B / W or select specific frames in the video and some audio-tasks, etc.) but the problem is that if the user wants to adjust the brightness or contrast of the video, it requires a video preview, but it does not support I ffmpeg ffmpeg needs to encode the video before the preview , so my question is how I can get a preview in real time using ffmpeg

Thanks in advance (sorry for the problems associated with the grammar in the question)