First cut of option to strip silence from audio regions, as per mantis #1623

git-svn-id: svn://localhost/ardour2/branches/3.0@5010 d708f5d6-7413-0410-9779-e7cbd77b26cf

7 files changed, 75 insertions, 6 deletions

diff --git a/libs/ardour/SConscript b/libs/ardour/SConscript
index d30c276840..27cffdff9d 100644
--- a/libs/ardour/SConscript
+++ b/libs/ardour/SConscript
@@ -159,6 +159,7 @@ sndfileimportable.cc
 sndfilesource.cc
 source.cc
 source_factory.cc
+strip_silence.cc
 svn_revision.cc
 tape_file_matcher.cc
 template_utils.cc
diff --git a/libs/ardour/ardour/audioregion.h b/libs/ardour/ardour/audioregion.h
index 917578191f..b2e2aa3eef 100644
--- a/libs/ardour/ardour/audioregion.h
+++ b/libs/ardour/ardour/audioregion.h
@@ -106,7 +106,7 @@ class AudioRegion : public Region
 	virtual nframes_t master_read_at (Sample *buf, Sample *mixdown_buf, float *gain_buf,
 			sframes_t position, nframes_t cnt, uint32_t chan_n=0) const;
 	
-	virtual nframes_t read_raw_internal (Sample*, sframes_t, nframes_t) const;
+	virtual nframes_t read_raw_internal (Sample*, sframes_t, nframes_t, int channel) const;
 
 	XMLNode& state (bool);
 	int      set_state (const XMLNode&);
@@ -162,6 +162,7 @@ class AudioRegion : public Region
 	void resume_fade_out ();
 
 	int get_transients (AnalysisFeatureList&, bool force_new = false);
+	std::list<std::pair<nframes_t, nframes_t> > find_silence (Sample, nframes_t) const;
 
   private:
 	friend class RegionFactory;
diff --git a/libs/ardour/ardour/crossfade.h b/libs/ardour/ardour/crossfade.h
index bd3ee914f9..4afa38126c 100644
--- a/libs/ardour/ardour/crossfade.h
+++ b/libs/ardour/ardour/crossfade.h
@@ -170,7 +170,7 @@ class Crossfade : public ARDOUR::AudioRegion
 	bool update ();
 
   protected:
-	nframes_t read_raw_internal (Sample*, sframes_t, nframes_t) const;	
+	nframes_t read_raw_internal (Sample*, sframes_t, nframes_t, int) const;	
 };
 
 
diff --git a/libs/ardour/audioregion.cc b/libs/ardour/audioregion.cc
index 085296281c..b3fd239c59 100644
--- a/libs/ardour/audioregion.cc
+++ b/libs/ardour/audioregion.cc
@@ -1062,9 +1062,9 @@ AudioRegion::separate_by_channel (Session& session, vector<boost::shared_ptr<Reg
 }
 
 nframes_t
-AudioRegion::read_raw_internal (Sample* buf, sframes_t pos, nframes_t cnt) const
+AudioRegion::read_raw_internal (Sample* buf, sframes_t pos, nframes_t cnt, int channel) const
 {
-	return audio_source()->read  (buf, pos, cnt);
+	return audio_source()->read (buf, pos, cnt, channel);
 }
 
 int
@@ -1184,7 +1184,7 @@ AudioRegion::normalize_to (float target_dB)
 
 			/* read it in */
 
-			if (read_raw_internal (buf, fpos, to_read) != to_read) {
+			if (read_raw_internal (buf, fpos, to_read, 0) != to_read) {
 				return;
 			}
 			
@@ -1438,6 +1438,71 @@ then quit ardour and restart."));
 	return 0;
 }
 
+/** Find areas of `silence' within a region.
+ *
+ *  @param threshold Threshold below which signal is considered silence (as a sample value)
+ *  @param min_length Minimum length of silent period to be reported.
+ *  @return Silent periods; first of pair is the offset within the region, second is the length of the period
+ */
+
+std::list<std::pair<nframes_t, nframes_t> >
+AudioRegion::find_silence (Sample threshold, nframes_t min_length) const
+{
+	nframes_t const block_size = 64 * 1024;
+	Sample loudest[block_size];
+	Sample buf[block_size];
+	
+	nframes_t pos = _start;
+	nframes_t const end = _start + _length - 1;
+
+	std::list<std::pair<nframes_t, nframes_t> > silent_periods;
+
+	bool in_silence = false;
+	nframes_t silence_start = 0;
+	bool silence;
+
+	while (pos < end) {
+
+		nframes_t const to_read = min (end - pos, block_size);
+
+		/* fill `loudest' with the loudest absolute sample at each instant, across all channels */
+		memset (loudest, 0, sizeof (Sample) * block_size);
+		for (uint32_t n = 0; n < n_channels(); ++n) {
+
+			read_raw_internal (buf, pos, block_size, n);
+			for (nframes_t i = 0; i < block_size; ++i) {
+				loudest[i] = max (loudest[i], abs (buf[i]));
+			}
+		}
+
+		/* now look for silence */
+		for (nframes_t i = 0; i < block_size; ++i) {
+			silence = abs (loudest[i]) < threshold;
+			if (silence && !in_silence) {
+				/* non-silence to silence */
+				in_silence = true;
+				silence_start = pos + i;
+			} else if (!silence && in_silence) {
+				/* silence to non-silence */
+				in_silence = false;
+				if (pos + i - 1 - silence_start >= min_length) {
+					silent_periods.push_back (std::make_pair (silence_start, pos + i - 1));
+				}
+			}
+		}
+
+		pos += block_size;
+	}
+
+	if (in_silence && end - 1 - silence_start >= min_length) {
+		/* last block was silent, so finish off the last period */
+		silent_periods.push_back (std::make_pair (silence_start, end));
+	}
+
+	return silent_periods;
+}
+
+
 extern "C" {
 
 	int region_read_peaks_from_c (void *arg, uint32_t npeaks, uint32_t start, uint32_t cnt, intptr_t data, uint32_t n_chan, double samples_per_unit) 
diff --git a/libs/ardour/crossfade.cc b/libs/ardour/crossfade.cc
index 8aad53765a..c258a9bf73 100644
--- a/libs/ardour/crossfade.cc
+++ b/libs/ardour/crossfade.cc
@@ -271,7 +271,7 @@ Crossfade::initialize ()
 }	
 
 nframes_t 
-Crossfade::read_raw_internal (Sample* buf, sframes_t start, nframes_t cnt) const
+Crossfade::read_raw_internal (Sample* buf, sframes_t start, nframes_t cnt, int channel) const
 {
 	// FIXME: Why is this disabled?
 #if 0
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index dcca313c79..a90a2b244d 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -1638,3 +1638,4 @@ Region::invalidate_transients ()
 	_transients.clear ();
 }
 
+
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index 342ca79a0a..b087e194c2 100644
--- a/libs/ardour/wscript
+++ b/libs/ardour/wscript
@@ -198,6 +198,7 @@ def build(bld):
 		sndfilesource.cc
 		source.cc
 		source_factory.cc
+                strip_silence.cc
 		svn_revision.cc
 		tape_file_matcher.cc
 		template_utils.cc