UPMIX PLUGIN
============

The upmix plugin is an easy-to-use plugin for upmixing from 1 or 2
channel stream to 4 or 6-channel stream.  The number of channels to be
expanded is determined by the slave PCM.  For example, the following
PCM defines upmixing to 5.1 from 2-6 channels input:

	pcm.upmix51 {
		type upmix
		slave.pcm "surround51"
	}

You can use this PCM as a default one by defining below:

	pcm.!default "plug:upmix51"

The upmix plugin copies left and right channels to rear left and right
with a certain delay.  The delay size can be specified by "delay" PCM
option in msec.  For example, to set 10ms delay in the above case:

	pcm.upmix51 {
		type upmix
		slave.pcm "surround51"
		channels 6
		delay 10
	}

As default, 15ms delay is used.

The center and LFE channels are the average of sum of left and right
signals.

The accepted format is currently only S16.