From 81182b5bf69e06f67b3ccbca46860ac8e6387d2f Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Sun, 8 Jun 2014 11:18:18 +0200
Subject: prepare MIDI latency measurement (backend)

---
 libs/ardour/mididm.cc | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 libs/ardour/mididm.cc

(limited to 'libs/ardour/mididm.cc')

diff --git a/libs/ardour/mididm.cc b/libs/ardour/mididm.cc
new file mode 100644
index 0000000000..6549544efb
--- /dev/null
+++ b/libs/ardour/mididm.cc
@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2013-2014 Robin Gareus <robin@gareus.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "ardour/mididm.h"
+#include "ardour/port_engine.h"
+
+using namespace ARDOUR;
+
+MIDIDM::MIDIDM (framecnt_t sample_rate)
+  : _sample_rate (sample_rate)
+  , _monotonic_cnt (sample_rate)
+  , _last_signal_tme (0)
+  , _cnt_total (0)
+  , _dly_total (0)
+  , _min_delay (INT32_MAX)
+  , _max_delay (0)
+  , _avg_delay (0)
+  , _var_m (0)
+  , _var_s (0)
+{
+
+}
+
+
+int MIDIDM::process (pframes_t nframes, PortEngine &pe, void *midi_in, void *midi_out)
+{
+	/* send midi event */
+	uint8_t obuf[3];
+	obuf[0] = 0xf2;
+	obuf[1] = (_monotonic_cnt)      & 0x7f;
+	obuf[2] = (_monotonic_cnt >> 7) & 0x7f;
+
+	pe.midi_clear(midi_out);
+	pe.midi_event_put (midi_out, 0, obuf, 3);
+
+	/* process incoming */
+	const pframes_t nevents = pe.get_midi_event_count (midi_in);
+	for (pframes_t n = 0; n < nevents; ++n) {
+		pframes_t timestamp;
+		size_t size;
+		uint8_t* buf;
+		pe.midi_event_get (timestamp, size, &buf, midi_in, n);
+
+		if (size != 3 || buf[0] != 0xf2 ) continue;
+
+		_last_signal_tme = _monotonic_cnt;
+
+		/* calculate time difference */
+#define MODX (16384)  // 1<<(2*7)
+#define MASK (0x3fff) // MODX - 1
+		const int64_t tc = (_monotonic_cnt + timestamp) & MASK;
+		const int64_t ti = (buf[2] << 7) | buf[1];
+		const int64_t tdiff = (MODX + tc - ti) % MODX;
+
+		/* running variance */
+		if (_cnt_total == 0) {
+			_var_m = tdiff;
+		} else {
+			const double var_m1 = _var_m;
+			_var_m = _var_m + ((double)tdiff - _var_m) / (double)(_cnt_total + 1);
+			_var_s = _var_s + ((double)tdiff - _var_m) * ((double)tdiff - var_m1);
+		}
+		/* average and mix/max */
+		++_cnt_total;
+		_dly_total += tdiff;
+		_avg_delay = _dly_total / _cnt_total;
+		if (tdiff < _min_delay) _min_delay = tdiff;
+		if (tdiff > _max_delay) _max_delay = tdiff;
+	}
+
+  _monotonic_cnt += nframes;
+	return 0;
+}
-- 
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