From 417f23ba4f8f625cff3a0cdc8a7b01d10415cece Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Fri, 16 Apr 2010 15:14:59 +0000
Subject: [PATCH] when a region has less channels than its diskstream needs,
 read a relevant channel instead (this makes mono regions in stereo tracks
 become effectively multi-mono)

git-svn-id: svn://localhost/ardour2/branches/2.0-ongoing@6915 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 libs/ardour/ardour/audiosource.h |  1 +
 libs/ardour/audioregion.cc       | 13 ++++++++++---
 libs/ardour/audiosource.cc       | 12 ++++++++++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/libs/ardour/ardour/audiosource.h b/libs/ardour/ardour/audiosource.h
index 20acd9fcd8..ef455f9735 100644
--- a/libs/ardour/ardour/audiosource.h
+++ b/libs/ardour/ardour/audiosource.h
@@ -90,6 +90,7 @@ class AudioSource : public Source, public boost::enable_shared_from_this<ARDOUR:
 
 	uint32_t read_data_count() const { return _read_data_count; }
 	uint32_t write_data_count() const { return _write_data_count; }
+	void dec_read_data_count(nframes_t);
 
  	int read_peaks (PeakData *peaks, nframes_t npeaks, nframes_t start, nframes_t cnt, double samples_per_visual_peak) const;
 
diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index 373f9fced7..a25ac839be 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -583,11 +583,18 @@ AudioRegion::_read_at (const SourceList& srcs, nframes_t limit,
 
 	} else {
 		
-		/* track is N-channel, this region has less channels; silence the ones
-		   we don't have.
+		/* track is N-channel, this region has less channels, so use a relevant channel
 		*/
 
-		memset (mixdown_buffer, 0, sizeof (Sample) * cnt);
+                uint32_t channel = n_channels() % chan_n;
+
+		if (srcs[channel]->read (mixdown_buffer, _start + internal_offset, to_read) != to_read) {
+			return 0; /* "read nothing" */
+		}
+                
+                /* adjust read data count appropriately since this was a duplicate read */
+                srcs[channel]->dec_read_data_count (to_read);
+
 	}
 
 	if (rops & ReadOpsFades) {
diff --git a/libs/ardour/audiosource.cc b/libs/ardour/audiosource.cc
index fbac57dc7c..2fc7fd18cd 100644
--- a/libs/ardour/audiosource.cc
+++ b/libs/ardour/audiosource.cc
@@ -1015,3 +1015,15 @@ AudioSource::check_for_analysis_data_on_disk ()
 
 	return ok;
 }
+
+void
+AudioSource::dec_read_data_count (nframes_t cnt)
+{
+        uint32_t val = cnt * sizeof (Sample);
+
+        if (val < _read_data_count) {
+                _read_data_count -= val;
+        } else { 
+                _read_data_count = 0;
+        }
+}