The transcribe.html provides you an option to listen to an audio or video recording and transcribe it along with adding timestamps.
You can use shortcuts to increase or decrease the speed, or forward or rewind the audio that is playing.
A demo is available at https://exain.com/transcribe/
It is a HTML5 script that uses Local Storage to save the data.
You do not need an internet connection to use it. Just open the transcribe.html file in your browser (Mozilla Firefox / Google Chrome / Safari), and select the file you wish to transcribe.