Misc fixes for upmix plugin

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

2 files changed, 42 insertions, 9 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.
 
diff --git a/mix/pcm_upmix.c b/mix/pcm_upmix.c
index ed8d041..9ca5bf4 100644
--- a/mix/pcm_upmix.c
+++ b/mix/pcm_upmix.c
@@ -290,8 +290,10 @@ static int upmix_init(snd_pcm_extplug_t *ext)
 
 	stype = (ext->slave_channels == 6) ? 1 : 0;
 	ctype = ext->channels - 1;
-	if (ctype < 0 || ctype >= 5)
+	if (ctype < 0 || ctype > 5) {
+		SNDERR("Invalid channel numbers for upmix: %d", ctype + 1);
 		return -EINVAL;
+	}
 	mix->upmix = do_upmix[ctype][stype];
 
 	if (mix->delay_ms) {
@@ -327,6 +329,7 @@ SND_PCM_PLUGIN_DEFINE_FUNC(upmix)
 	snd_pcm_upmix_t *mix;
 	snd_config_t *sconf = NULL;
 	static unsigned int chlist[2] = {4, 6};
+	unsigned int channels = 0;
 	int delay = 10;
 	int err;
 
@@ -350,6 +353,20 @@ SND_PCM_PLUGIN_DEFINE_FUNC(upmix)
 			}
 			delay = val;
 		}
+		if (strcmp(id, "channels") == 0) {
+			long val;
+			err = snd_config_get_integer(n, &val);
+			if (err < 0) {
+				SNDERR("Invalid value for %s", id);
+				return err;
+			}
+			channels = val;
+			if (channels != 4 && channels != 6 && channels != 0) {
+				SNDERR("channels must be 4, 6 or 0");
+				return -EINVAL;
+			}
+			continue;
+		}
 		SNDERR("Unknown field %s", id);
 		return -EINVAL;
 	}
@@ -382,9 +399,14 @@ SND_PCM_PLUGIN_DEFINE_FUNC(upmix)
 	snd_pcm_extplug_set_param_minmax(&mix->ext,
 					 SND_PCM_EXTPLUG_HW_CHANNELS,
 					 1, 6);
-	snd_pcm_extplug_set_slave_param_list(&mix->ext,
-					     SND_PCM_EXTPLUG_HW_CHANNELS,
-					     2, chlist);
+	if (channels)
+		snd_pcm_extplug_set_slave_param_minmax(&mix->ext,
+						       SND_PCM_EXTPLUG_HW_CHANNELS,
+						       channels, channels);
+	else
+		snd_pcm_extplug_set_slave_param_list(&mix->ext,
+						     SND_PCM_EXTPLUG_HW_CHANNELS,
+						     2, chlist);
 	snd_pcm_extplug_set_param(&mix->ext, SND_PCM_EXTPLUG_HW_FORMAT,
 				  SND_PCM_FORMAT_S16);
 	snd_pcm_extplug_set_slave_param(&mix->ext, SND_PCM_EXTPLUG_HW_FORMAT,