Move vari-speed into backend (resample ports)

Previously Ardour used a /local/ per track vari-speed mechanism.
Now that the disk-reader is a latency-compensated processor, the speed
of each disk-reader would need to be maintained locally, offset by each
disk-reader's output latency. Furthermore each disk-reader may
produce a different number of samples, depending on its global alignment.

This commit introduces port-data resampling directly at the engine-level:
Up/down-sample all input ports at the beginning, and down/up-sample output
port-data using the inverse ratio at the end of the session's process
cycle.
The session itself is unaware of the speed-change, and only needs to
handle transport speeds {-1, 0, +1}.

This also allows for aligned cue-monitoring and vari-speed recording,
and also pitch-shifts synthesized MIDI along.

1 files changed, 14 insertions, 8 deletions

diff --git a/libs/ardour/ardour/port.h b/libs/ardour/ardour/port.h
index e59df0cb03..18d56dd8df 100644
--- a/libs/ardour/ardour/port.h
+++ b/libs/ardour/ardour/port.h
@@ -106,7 +106,7 @@ public:
 	void set_private_latency_range (LatencyRange& range, bool playback);
 	const LatencyRange&  private_latency_range (bool playback) const;
 
-	void set_public_latency_range (LatencyRange& range, bool playback) const;
+	void set_public_latency_range (LatencyRange const& range, bool playback) const;
 	LatencyRange public_latency_range (bool playback) const;
 
 	virtual void reset ();
@@ -121,15 +121,16 @@ public:
 	virtual void realtime_locate () {}
 
 	bool physically_connected () const;
+	bool externally_connected () const;
 
 	PBD::Signal1<void,bool> MonitorInputChanged;
 	static PBD::Signal2<void,boost::shared_ptr<Port>,boost::shared_ptr<Port> > PostDisconnect;
 	static PBD::Signal0<void> PortDrop;
 	static PBD::Signal0<void> PortSignalDrop;
 
-	static void set_cycle_samplecnt (pframes_t n) {
-		_cycle_nframes = n;
-	}
+	static void set_speed_ratio (double s);
+	static void set_cycle_samplecnt (pframes_t n);
+
 	static samplecnt_t port_offset() { return _global_port_buffer_offset; }
 	static void set_global_port_buffer_offset (pframes_t off) {
 		_global_port_buffer_offset = off;
@@ -145,21 +146,26 @@ public:
 
 	static std::string state_node_name;
 
+	static pframes_t cycle_nframes () { return _cycle_nframes; }
+
 protected:
 
 	Port (std::string const &, DataType, PortFlags);
 
-        PortEngine::PortHandle _port_handle;
+	PortEngine::PortHandle _port_handle;
 
-	static bool	  _connecting_blocked;
-	static pframes_t  _global_port_buffer_offset;   /* access only from process() tree */
+	static bool	      _connecting_blocked;
 	static pframes_t  _cycle_nframes; /* access only from process() tree */
 
-	samplecnt_t _port_buffer_offset; /* access only from process() tree */
+	static pframes_t  _global_port_buffer_offset; /* access only from process() tree */
+	samplecnt_t       _port_buffer_offset; /* access only from process() tree */
 
 	LatencyRange _private_playback_latency;
 	LatencyRange _private_capture_latency;
 
+	static double _speed_ratio;
+	static const uint32_t _resampler_quality; /* also latency of the resampler */
+
 private:
 	std::string _name;  ///< port short name
 	PortFlags   _flags; ///< flags