readme file for the mixing

git-svn-id: http://svn.berlios.de/svnroot/repos/sems/trunk@448 8eb893ce-cfd4-0310-b710-fb5ebe64c474

apps/examples/mixin_announce/Readme.mixin_announce

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+mixin_announce
+
+This module demonstrates the AmAudioMixIn, used in the IVR, where
+it is called IvrAudioMixIn. The AmAudioMixIn is an audio device 
+that uses two AmAudio 'devices' (in the IVR: IvrAudioFile) as audio
+sources, plays the first one, and periodically mixes in the second one.
+The period, i.e. the time between two times mixing in the second audio,
+can be specified, as well as the level with which the second one is
+mixed into the first. The last parameter, a boolean, specifies whether
+playback of the second audio should be finished if the first is finished
+while mixing in the second.
+If level == 0, playback of the first is not continued when playing the 
+second, which means that it continues right where it was before 
+playback of the second started.
+
+IVR usage: 
+    init(IvrAudioFile first, IvrAudioFile second, 
+         int interval, float level, boolean finish)
+
+C++ usage:
+AmAudioMixIn::
+  AmAudioMixIn(AmAudio* A, AmAudioFile* B, 
+	       unsigned int interval, double level, 
+	       bool finish_b_while_mixing = false);
+