do tempo estimation within AudioSources, after capture and upon import

we read 10 seconds from the middle of the data; not infallible but a reasonable
first pass at a heuristic.

libs/ardour/ardour/audiosource.h

@@ -95,6 +95,8 @@ class LIBARDOUR_API AudioSource : virtual public Source, public ARDOUR::AudioRea
 	/** @return true if the each source sample s must be clamped to -1 < s < 1 */
 	virtual bool clamped_at_unity () const = 0;
 
+	void estimate_tempo ();
+
   protected:
 	static bool _build_missing_peakfiles;
 	static bool _build_peakfiles;

libs/ardour/ardour/source.h

@@ -156,6 +156,8 @@ public:
 	bool get_segment_descriptor (TimelineRange const &, SegmentDescriptor&);
 	int set_segment_descriptor (SegmentDescriptor const &, bool replace = false);
 
+	void copy_segment_descriptors (Source const & other);
+
   protected:
 	DataType            _type;
 	Flag                _flags;

libs/ardour/audiosource.cc

@@ -61,6 +61,7 @@
 #include "ardour/rc_configuration.h"
 #include "ardour/runtime_functions.h"
 #include "ardour/session.h"
+#include "ardour/utils.h"
 
 #include "pbd/i18n.h"
 
@@ -131,6 +132,46 @@ AudioSource::~AudioSource ()
 	delete [] peak_leftovers;
 }
 
+void
+AudioSource::estimate_tempo ()
+{
+	/* CALLER MUST HOLD WRITER LOCK */
+
+	const samplecnt_t ten_seconds = _session.sample_rate() * 10;
+
+	if (length().samples() < ten_seconds) {
+		return;
+	}
+
+	samplecnt_t data_size = ten_seconds;
+	std::unique_ptr<Sample[]> data (new Sample[data_size]);
+
+	/* Read ten seconds from the middle of the data */
+
+	if (read_unlocked (data.get(), std::max ((samplecnt_t) 0, (length().samples() - data_size) / 2), data_size) == data_size) {
+
+		double tempo;
+		double beatcount;
+		Temporal::Tempo t (120, 4);
+		Temporal::Meter m (4, 4);
+		TimelineRange r (timepos_t (0), timepos_t (0) + length(), 0);
+
+		estimate_audio_tempo_source (r, shared_from_this(), data.get(), data_size, _session.sample_rate(), tempo, m, beatcount);
+		t = Temporal::Tempo (tempo, 4);
+
+		SegmentDescriptor sd;
+
+		sd.set_tempo (t);
+		sd.set_meter (m);
+		sd.set_position (0);
+		sd.set_duration (length().samples());
+
+		/* One segment descriptor to rule them all */
+
+		set_segment_descriptor (sd, true);
+	}
+}
+
 XMLNode&
 AudioSource::get_state () const
 {
@@ -1165,6 +1206,9 @@ AudioSource::available_peaks (double zoom_factor) const
 
 void
 AudioSource::mark_streaming_write_completed (const WriterLock& lock, Temporal::timecnt_t const &)
+{
+	estimate_tempo ();
+
 	{
 		Glib::Threads::Mutex::Lock lm (_peaks_ready_lock);
 
@@ -1172,3 +1216,5 @@ AudioSource::mark_streaming_write_completed (const WriterLock& lock, Temporal::t
 			PeaksReady (); /* EMIT SIGNAL */
 		}
 	}
+}
+

libs/ardour/sndfilesource.cc

@@ -329,6 +329,8 @@ SndFileSource::SndFileSource (Session& s, const AudioFileSource& other, const st
 		tbuf.modtime = statbuf.st_mtime; // = time ((time_t*) 0);
 		g_utime (path.c_str(), &tbuf);
 	}
+
+	copy_segment_descriptors (other);
 }
 
 void

libs/ardour/source.cc

@@ -582,3 +582,9 @@ Source::set_segment_descriptor (SegmentDescriptor const & sr, bool replace)
 
 	return 0;
 }
+
+void
+Source::copy_segment_descriptors (Source const & other)
+{
+	segment_descriptors = other.segment_descriptors;
+}

libs/ardour/source_factory.cc

@@ -252,13 +252,14 @@ SourceFactory::createExternal (DataType type, Session& s, const string& path,
 {
 	if (type == DataType::AUDIO) {
 		try {
-			Source*                   src = new SndFileSource (s, path, chn, flags);
+			AudioSource* src = new SndFileSource (s, path, chn, flags);
 			std::shared_ptr<Source> ret (src);
 			BOOST_MARK_SOURCE (ret);
 			if (setup_peakfile (ret, defer_peaks)) {
 				throw failed_constructor ();
 			}
 			ret->check_for_analysis_data_on_disk ();
+			src->estimate_tempo ();
 			if (announce) {
 				SourceCreated (ret);
 			}
@@ -268,13 +269,14 @@ SourceFactory::createExternal (DataType type, Session& s, const string& path,
 
 #ifdef HAVE_COREAUDIO
 		try {
-			Source*                   src = new CoreAudioSource (s, path, chn, flags);
+			AudioSource* src = new CoreAudioSource (s, path, chn, flags);
 			std::shared_ptr<Source> ret (src);
 			BOOST_MARK_SOURCE (ret);
 			if (setup_peakfile (ret, defer_peaks)) {
 				throw failed_constructor ();
 			}
 			ret->check_for_analysis_data_on_disk ();
+			src->estimate_tempo ();
 			if (announce) {
 				SourceCreated (ret);
 			}
@@ -415,8 +417,7 @@ SourceFactory::createFromPlaylist (DataType type, Session& s, std::shared_ptr<Pl
 					start = timecnt_t::zero (Temporal::AudioTime);
 				}
 
-				Source* src = new AudioPlaylistSource (s, orig, name, ap, chn, start, len, Source::Flag (0));
+				AudioSource* src = new AudioPlaylistSource (s, orig, name, ap, chn, start, len, Source::Flag (0));
-
 				std::shared_ptr<Source> ret (src);
 
 				if (setup_peakfile (ret, defer_peaks)) {
@@ -424,6 +425,7 @@ SourceFactory::createFromPlaylist (DataType type, Session& s, std::shared_ptr<Pl
 				}
 
 				ret->check_for_analysis_data_on_disk ();
+				src->estimate_tempo ();
 				SourceCreated (ret);
 				return ret;
 			}