Adding on the fly volume normalization support. Code originally from mplayer, ported by syscrash, cleaned up by avuton, and further cleaned up by me (jat).

git-svn-id: https://svn.musicpd.org/mpd/trunk@4424 09075e82-0dd4-0310-85a5-a0d7c8717e4f

doc/mpd.conf.5

@@ -92,6 +92,9 @@ Musepack, and MP3 (through ID3v2 replaygain tags, not APEv2) are supported.
 .B replaygain_preamp <-15 to 15>
 This is the gain (in dB) applied to songs with replaygain tags.
 .TP
+.B volume_normalization <yes or no>
+If yes, mpd will normalize the volume of songs as they play.  Default is no.
+.TP
 .B audio_buffer_size <size in KiB>
 This specifies the size of the audio output buffer that mpd uses.  The default
 is 2048.

doc/mpdconf.example

@@ -126,7 +126,7 @@ pid_file 		"~/.mpd/mpd.pid"
 ##########################################################
 
 
-################# REPLAYGAIN #############################
+################# Normalization ##########################
 #
 # Use Replay Gain (album or track)
 #	http://www.replaygain.org
@@ -138,6 +138,13 @@ pid_file 		"~/.mpd/mpd.pid"
 #
 #replaygain_preamp	"0"
 #
+# Normalization increases the amplitude of the audio
+# waveform to the maximum level without introducing any 
+# distortion into the recording. This option will 
+# normalize when replaygain is not on, utilizing the 
+# CPU for calculation.
+#
+#volume_normalization	"yes"
 ##########################################################