fix incorrect handling of MIDI data by AsyncMIDIPort

This type of MIDI port fetches all of its data from inside ::cycle_start(),
and delivers it to a FIFO connected to another thread (typically a
control surface).

Unlike regular MidiPorts, which will be read from inside a Session::process()
call, these ports will read their data once per AudioEngine::process() cycle.
They therefore cannot use MidiPort::get_midi_buffer() which scales and adjusts
event timestamps as if the data is being accessed from within Session::process().

It is still an open question whether or not AsyncMIDIPort::cycle_start() should
still scale event timestamps by speed. In some respects it seems more appropriate
to do so, and the reading thread (e.g. a control surface) doesn't care about
the "nframes" limit on timestamps that exists for calls within a Session::process()
tree. For now, leave the timestamps unscaled by speed.

1 files changed, 24 insertions, 13 deletions

diff --git a/libs/ardour/async_midi_port.cc b/libs/ardour/async_midi_port.cc
index 1e898764d2..06a51279fe 100644
--- a/libs/ardour/async_midi_port.cc
+++ b/libs/ardour/async_midi_port.cc
@@ -131,23 +131,35 @@ AsyncMIDIPort::cycle_start (MIDI::pframes_t nframes)
 	*/
 
 	if (ARDOUR::Port::receives_input()) {
-		MidiBuffer& mb (get_midi_buffer (nframes));
-		samplecnt_t when;
 
-		if (have_timer) {
-			when = timer ();
-		} else {
-			when = AudioEngine::instance()->sample_time_at_cycle_start();
-		}
+		void* buffer = port_engine.get_buffer (_port_handle, nframes);
+		const pframes_t event_count = port_engine.get_midi_event_count (buffer);
+
+		for (pframes_t i = 0; i < event_count; ++i) {
 
-		for (MidiBuffer::iterator b = mb.begin(); b != mb.end(); ++b) {
-			if (!have_timer) {
-				when += (*b).time();
+			pframes_t timestamp;
+			size_t size;
+			uint8_t const* buf;
+
+			port_engine.midi_event_get (timestamp, size, &buf, buffer, i);
+
+			if (buf[0] == 0xfe) {
+				/* throw away active sensing */
+				continue;
 			}
-			input_fifo.write (when, Evoral::NO_EVENT, (*b).size(), (*b).buffer());
+
+			samplecnt_t when;
+
+			if (have_timer) {
+				when = timer ();
+			} else {
+				when = AudioEngine::instance()->sample_time_at_cycle_start() + timestamp;
+			}
+
+			input_fifo.write (when, Evoral::NO_EVENT, size, buf);
 		}
 
-		if (!mb.empty()) {
+		if (event_count) {
 			_xthread.wakeup ();
 		}
 
@@ -346,4 +358,3 @@ AsyncMIDIPort::is_process_thread()
 {
 	return pthread_equal (pthread_self(), _process_thread);
 }
-