###Background
As a terminal junkie, I've started messing around with a combination of mpd (Music Player Daemon) and a player, ncmpcpp (NCurses Media Player Client C++).
I installed these via Homebrew - a simple brew install mpd ncmpcpp
. A bit of configuration later, and the apps are running quite nicely. The effect is actually rather impressive:
The problem I run into is when I want to run mpd
automatically instead of having it launch in my terminal. It comes with a launchd
plist, so I install that, and it appears to work - The problem is that whatever I'm playing, be that an MP3, streaming audio from a server, or whatever, the audio stutters every 5 seconds
This absolutely does not happen when mpd
is invoked directly from the command line, only when it's fired off via launchd.
Here's what the plist looks like:
<!--homebrew.mxcl.mpd.plist-->
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>KeepAlive</key>
<true/>
<key>Label</key>
<string>homebrew.mxcl.mpd</string>
<key>ProcessType</key>
<string>Interactive</string>
<key>ProgramArguments</key>
<array>
<string>/usr/local/opt/mpd/bin/mpd</string>
<string>--no-daemon</string>
</array>
<key>RunAtLoad</key>
<true/>
<key>WorkingDirectory</key>
<string>/usr/local</string>
</dict>
</plist>
The "ProcessType" interactive was added by me in an attempt to force launchd to give the daemon higher priority, to no effect.
###Things I've already eliminated
- CPU / Disk IO
The system is relatively quiet - during the stutters, mpd is not even on the top 25 for memory or CPU usage, and load is well below 1.0
- Incorrect environment causing bad config settings to be loaded
My mpd config is the one being loaded from ~/.mpdconf
- same as it is when I run it by hand.
This appears to be a symptom of the way launchd chooses to handle the process.
###The ultimate question Why is the daemon so misbehaved when run under launchd, but not when run via terminal?
###Bonus question: What about the way launchd kicks off processes could be making this behavior manifest?