Misc fixes for upmix plugin

- Add channel option to specify the output channels explicitly
- Fix 6-channel input

1 files changed, 16 insertions, 5 deletions

diff --git a/doc/upmix.txt b/doc/upmix.txt
index b8a6da4..56720a4 100644
--- a/doc/upmix.txt
+++ b/doc/upmix.txt
@@ -1,10 +1,10 @@
 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:
+The upmix plugin is an easy-to-use plugin for upmixing to 4 or
+6-channel stream.  The number of channels to be expanded is determined
+by the slave PCM or explicitly via channel option.  For example, the
+following PCM defines upmixing to 5.1 from 1-6 channels input:
 
 	pcm.upmix51 {
 		type upmix
@@ -22,12 +22,23 @@ 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 channel option specifies the number of channels of output.  Either
+4 or 6 channels are supported.  When 0 is passed, the plugin tries 4
+or 6 channels appropriately suitable for the slave pcm.  The channel
+option is useful if the slave PCM has no strict input condition (like
+plug or route plugin).
+
+	pcm.myupmix {
+		type upmix
+		slave.pcm "something"
+		channels 6
+	}
+
 The center and LFE channels are the average of sum of left and right
 signals.