From 7895b5ec7e01c5ffecc510fbe4313b2470ff3b4b Mon Sep 17 00:00:00 2001
From: Jonathan Moore Liles <j.liles@unix.net>
Date: Sun, 11 Oct 2020 23:16:26 -0700
Subject: [PATCH] Mixer: Allow Mono Pan module to be added a stereo chain. This
 converts the signal to mono and then pans the result. Useful for auditioning
 a mix in mono.

---
 mixer/src/Mono_Pan_Module.C | 34 +++++++++++++++++++++++++++++-----
 mixer/src/Mono_Pan_Module.H |  2 +-
 2 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/mixer/src/Mono_Pan_Module.C b/mixer/src/Mono_Pan_Module.C
index 9eac660..3ed6810 100644
--- a/mixer/src/Mono_Pan_Module.C
+++ b/mixer/src/Mono_Pan_Module.C
@@ -66,8 +66,22 @@ Mono_Pan_Module::handle_sample_rate_change ( nframes_t n )
 }
 
 bool
-Mono_Pan_Module::configure_inputs ( int )
+Mono_Pan_Module::configure_inputs ( int n )
 {
+    THREAD_ASSERT( UI );
+
+    int on = audio_input.size();
+
+    if ( n > on )
+    {
+	add_port( Port( this, Port::INPUT, Port::AUDIO ) );
+    }
+    else if ( n < on )
+    {
+	audio_input.back().disconnect();
+	audio_input.pop_back();	
+    }
+    
     return true;
 }
 
@@ -82,7 +96,10 @@ Mono_Pan_Module::process ( nframes_t nframes )
 {
     if ( unlikely( bypass() ) )
     {
-        buffer_copy( (sample_t*)audio_output[1].buffer(), (sample_t*)audio_input[0].buffer(), nframes );
+	if ( audio_input.size() == 1 )
+	{
+	    buffer_copy( (sample_t*)audio_output[1].buffer(), (sample_t*)audio_input[0].buffer(), nframes );
+	}
     }
     else
     {
@@ -90,11 +107,18 @@ Mono_Pan_Module::process ( nframes_t nframes )
 
         sample_t gainbuf[nframes];            
         bool use_gainbuf = smoothing.apply( gainbuf, nframes, gt );
-        
+
+	if ( audio_input.size() == 2 )
+	{
+	    /* convert stereo to mono */
+	    buffer_mix( (sample_t*)audio_input[0].buffer(),
+			(sample_t*)audio_input[1].buffer(),
+			nframes );
+	}
+	
         if ( unlikely( use_gainbuf ) )
         {            
-            /* right channel */
-                
+            /* right channel */                
             buffer_copy_and_apply_gain_buffer( (sample_t*)audio_output[1].buffer(),
                                                (sample_t*)audio_input[0].buffer(),
                                                gainbuf,
diff --git a/mixer/src/Mono_Pan_Module.H b/mixer/src/Mono_Pan_Module.H
index 7ede987..d94f93a 100644
--- a/mixer/src/Mono_Pan_Module.H
+++ b/mixer/src/Mono_Pan_Module.H
@@ -33,7 +33,7 @@ public:
 
     const char *name ( void ) const { return "Mono Pan"; }
 
-    int can_support_inputs ( int n ) { return ( n == 1 ) ? 2 : -1; }
+    int can_support_inputs ( int n ) { return ( n == 1 || n == 2 ) ? 2 : -1; }
     bool configure_inputs ( int n );
 
     LOG_CREATE_FUNC( Mono_Pan_Module );