How to advance to next song in playlist using Mplayer controlled by a named pipe in Python

Question

I have a python script that controls (via a named pipe) an instance of mplayer in slave mode that's playing MP3s. Everything works as expected, but I can't for the life of me figure out how to advance the playlist. I can echo commands and pause/stop/mute/quit mplayer from another terminal window, but the key binding to advance to the next song is the page up key... Obviously I can't echo "->" /tmp/fifo The mplayer documentation doesn't seem to have any solution to this as far as I can tell.

So far I've spent about an hour attempting to figure this out (it seems like it should be trivial, no?) but either my Google-fu is weak or the information isn't out there... I've thought about editing the keybindings of mplayer's Python interface but that seems like a lot of work for something so minor.

Any advice would be appreciated.

I've tried searching the mplayer docs and online. I was expecting a method to advance the playlist using a named pipe that didn't require a special character.

Answer 1

Answering this in case it helps anyone else:

So it turns out that it's not as complicated as I was making it. Mplayer expects special keys (arrow keys, etc) when it's running in "normal" mode--for want of a better word--but when it's is running in slave mode, the commands are all "words" of normal characters. So you can echo "pt_step +1" >> tmp/fifo and get it to advance to the next item in the playlist, rather than having to send a special character to stdin.

In my Python script, I just set the value of a variable command to echo "**value**" >> tmp/fifo and used os.system(command) to write to the pipe.

Answer 2

Page Up, Page Down, arrow keys and a few other have key codes that are composed by escape sequences - and IIRC, will even change depending on the terminal mode you are on.

I have the proper codes listed on the source code of a project of mine (terminedia) - you can check them here - https://github.com/jsbueno/terminedia/blob/5f1dfec7204715a29008543cb26bb9414be5f257/terminedia/input.py#L47 - I'd say that injecting these codes on MPlayer's stdin, the special keys should just work.

(If you are, like it seems, creating a Text User Interface for Mplayer from a terminal, you might want to take terminedia for a tour: for one, you can read the keyboard and mouse events in real time)