There's plenty of tools for editing videos like INDE, FFMPEG and etc.
INDE has so many functionality to join videos and images.
If you decide to use FFMPEG then this link provides steps for integration of this tool
Other helpful links:
FFMPEG:Multiple Image frames + 1 Audio =1 Video
Android make animated video from list of images
Android ffmpeg: create video from sequnce of images using jni
Combine an image into audio file and make a video file in android programmatically
Video creation from series of images?
How to Build Android Applications Based on FFmpeg by An Example
