Here is a nice application which allows you to reduce the size of any video in your mobile phone. When we try to send videos on whatsapp , if the video is big we will lose our precious time and mobile data . To avoid this we can use the application called Video Dieter, which is available on google play store and itunes. So you can use this application in your android smartphone and iphone.
The application also allows you to capture images from videos and change background music of the videos.The conversion of videos from large file size to small file size will affect the video quality , but it maintain a quality.