Make resampler reset idempotent

libs/ardour/audio_port.cc

@@ -69,7 +69,6 @@ AudioPort::cycle_start (pframes_t nframes)
 		_buffer->prepare ();
 	} else if (!externally_connected ()) {
 		/* ardour internal port, just silence input, don't resample */
-		// TODO reset resampler only once
 		_src.reset ();
 		memset (_data, 0, _cycle_nframes * sizeof (float));
 	} else {

libs/zita-resampler/vmresampler.cc

@@ -33,6 +33,7 @@ VMResampler::VMResampler (void)
   , _buff  (0)
   , _c1 (0)
   , _c2 (0)
+  , _reset (false)
 {
 	reset ();
 }
@@ -91,6 +92,7 @@ VMResampler::clear (void)
 	_pstep = 0;
 	_qstep = 0;
 	_wstep = 1;
+	_reset = false;
 	reset ();
 }
 
@@ -144,6 +146,7 @@ int
 VMResampler::reset (void)
 {
 	if (!_table) return 1;
+	if (_reset) return 0;
 
 	inp_count = 0;
 	out_count = 0;
@@ -155,6 +158,7 @@ VMResampler::reset (void)
 
 	memset (_buff, 0, sizeof(float) * (_nread + 249));
 	_nread -= _table->_hl - 1;
+	_reset = true;
 	return 0;
 }
 
@@ -175,6 +179,8 @@ VMResampler::process (void)
 	dp = _pstep;
 	n = 2 * hl - nr;
 
+	_reset = false;
+
 #if 1
 	/* optimized full-cycle no-resampling */
 	if (dp == np && _qstep == np && nr == 1 && inp_count == out_count) {

libs/zita-resampler/zita-resampler/vmresampler.h

@@ -66,6 +66,7 @@ private:
 	float               *_buff;
 	float               *_c1;
 	float               *_c2;
+	bool                 _reset;
 };
 
 };