I read this on a Gentoo forum today about Alsa’s DMIX plugin:
I mean, why can’t they make a _transparent_ software mixer? Why must every software be “updated” and “configured” to support the software mixing thing? Why on Earth couldn’t they make a plugin that needs no attention from the actual software, but just lets the software open and open the sound device? Why must mplayer, arts and others _know_ about the dmix plugin and _select_ it? That is not transparent.
The guy is right on. This is one of Linux’s main problems. Although we have as a hacker tenet to never reinvent the wheel, we also have a shitload of libraries and ways of doing things, and sometimes it leads to this awful situation: where you want to get software mixing of audio to work, but it will only work if you enable a mixing plugin in each application.