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, 8 insertions, 4 deletions

diff --git a/libs/ardour/ardour/audio_port.h b/libs/ardour/ardour/audio_port.h
index 384de3ef5d..4224a88d55 100644
--- a/libs/ardour/ardour/audio_port.h
+++ b/libs/ardour/ardour/audio_port.h
@@ -21,6 +21,8 @@
 #ifndef __ardour_audio_port_h__
 #define __ardour_audio_port_h__
 
+#include "zita-resampler/vmresampler.h"
+
 #include "ardour/port.h"
 #include "ardour/audio_buffer.h"
 
@@ -49,12 +51,14 @@ class LIBARDOUR_API AudioPort : public Port
 	friend class PortManager;
 	AudioPort (std::string const &, PortFlags);
 
-        /* special access for PortManager only (hah, C++) */
-        Sample* engine_get_whole_audio_buffer ();
+	/* special access for PortManager only (hah, C++) */
+	Sample* engine_get_whole_audio_buffer ();
 
   private:
-	AudioBuffer* _buffer;
-        bool         _buf_valid;
+	AudioBuffer*            _buffer;
+	ArdourZita::VMResampler _src;
+	Sample*                 _data;
+	bool                    _buf_valid;
 };
 
 } // namespace ARDOUR