Apple Provides library for video and audio editing library that is AVFoundation
Please Refer that library
You can check the sample code for merging videos and also adding images on video on the below link
https://github.com/darcyliu/SampleCode/tree/master/AVSimpleEditoriOS
I the class AVSEAddWatermarkCommand you will find watermarkLayerForSize method which add text layer in the same way you can add image. use below method to add image.
you also need to understand the AVMutableCompositionTrack
class this which is used in AVSEAddMusicCommand
this will help you. you can use the same class to merge videos.
- (CALayer*)imageLayerForSize:(CGSize)videoSize
{
// Create a layer for the title
CALayer *imageLayer = [CALayer layer];
imageLayer.bounds = CGRectMake(0, 0, videoSize.width, videoSize.height);
imageLayer.contents = (id)[UIImage imageNamed:@"myimage.png"];
return imageLayer;
}
I hope you will get your answer. still if you have any problem please comment it.