i am sameer ,persuing btech(CS) in indore ,i have an predesigned algorithm for your project,actually this app follow two concepts,firstly when on every incoming and outgoing call ,this will generate an dragable popup window with textview on dialer screen like truecaller and secondaly it will only record voice of person on other side or the voice of speaker and simply convert that voice into text in pop up window's textview like a normal voice to text converter...