amixer, alsamixer: Add description of volume-mapping

Signed-off-by: Takashi Iwai <tiwai@suse.de>

alsamixer/alsamixer.1

@@ -157,6 +157,19 @@ Quit the program with \fIALT Q\fP, or by hitting \fIESC\fP.
 Please note that you might need to hit \fIESC\fP twice on some terminals
 since it's regarded as a prefix key.
 
+.SH VOLUME MAPPING
+In \fBalsamixer\fP, the volume is mapped to a value that is more natural
+for a human ear.  The mapping is designed so that the position in the
+interval is proportional to the volume as a human ear would perceive
+it, i.e. the position is the cubic root of the linear sample
+multiplication factor.  For controls with a small range (24 dB or
+less), the mapping is linear in the dB values so that each step has
+the same size visually.
+
+Only for controls without dB information, a linear mapping of the
+hardware volume register values is used (this is the same algorithm as
+used in the old \fBalsamixer\fP).
+
 .SH SEE ALSO
 \fB
 amixer(1),

amixer/amixer.1

@@ -104,10 +104,21 @@ The commands to unmatched ids are ignored without errors too.
 .TP
 \fI\-h\fP 
 Help: show syntax.
+
 .TP
 \fI\-q\fP
 Quiet mode. Do not show results of changes.
 
+.TP
+\fI\-R\fP 
+Use the raw value for evaluating the percentage representation.
+This is the default mode.
+
+.TP
+\fI\-M\fP 
+Use the mapped volume for evaluating the percentage representation
+like \fBalsamixer\fR, to be more natural for human ear.
+
 .SH EXAMPLES
 
 .TP
@@ -134,8 +145,14 @@ will set the third soundcard's second line playback volume(s) to 40%
 \fBamixer \-c 2 cset numid=34 40%\fR
 will set the 34th soundcard element to 40%
 
+.SH SEE ALSO
+\fB
+alsamixer(1)
+\fP
+
 .SH BUGS 
 None known.
+
 .SH AUTHOR
 \fBamixer\fP is by Jaroslav Kysela <perex@perex.cz>.
 This document is by Paul Winkler <zarmzarm@erols.com> and Jaroslav Kysela <perex@perex.cz>.