I wrote this to help us select timestamps for the start and end of Q&A session recordings for EmacsConf 2021. Finding the right time in MPV was hard because it didn’t have a waveform view. Audacity could show waveforms, but it didn’t have an easy way to copy the timestamp. So the obvious answer is, of course, to make the text editor do the job. Yay Emacs!

It’s very experimental and I don’t know if it’ll work for anyone else. If you want to use it, you will also need mpv.el, the MPV media player, and the ffmpeg command-line tool. Here’s my workflow:

• M-x waveform-show to select the file.
• left-click on the waveform to copy the timestamp and start playing from there
• right-click to sample from that spot
• left and right to adjust the position, shift-left and shift-right to take smaller steps
• p to copy the current MPV position
• SPC to toggle pausing
• j to jump to a timestamp (hh:mm:ss or seconds)
• > to speed up, < to slow down

Sacha Chua (sacha@sachachua.com)