Speex Preprocessing Plugin

==========================

This plugin provides a pre-processing of a mono stream like denoise

using libspeex DSP API.  You can use the plugin with the plugin type

"speex" like below:

	pcm.my_pcm {

		type speex

		slave.pcm "default"

	}

Then record like

	% arecord -fdat -c1 -Dplug:my_pcm foo.wav

so that you'll get 48kHz mono stream with the denoising effect.

Right now, the plugin supports only a mono stream.

The accepted format is only S16.

The following parameters can be set optionally:

* frames

  This controls the frames of the intermediate buffer.  This

  corresponds to the latency of the filter.  As default it's 64.

* denoise

  A boolean value to enable/disable the denoise function.  Default is

  yes.

* agc

  A boolean value to enable/disable the auto-gain control function.

  Default is no.

* agc_level

  A float value for the automatic gain-control level.  Default is 8000.

* dereverb

  A boolean value to enable/disable dereverb function.  Default is no.

* echo

  A boolean value to enable/disable echo-cancellation function.

  Default is no.

* filter_length

  Number of samples of echo to cancel.  As default it's 256.

For example, you can enable agc like

	pcm.my_pcm {

		type speex

		slave.pcm "default"

		agc 1

		agc_level 8000

	}