From 01cedf0e050635e46e04a4f3c74ac9c37d3c767c Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Tue, 3 Jun 2014 01:00:58 +0200
Subject: [PATCH] ALSA backend: tweak midi parser (fix start mid sequence)

---
 libs/backends/alsa/alsa_rawmidi.cc | 8 ++++++++
 libs/backends/alsa/alsa_rawmidi.h  | 1 +
 2 files changed, 9 insertions(+)

diff --git a/libs/backends/alsa/alsa_rawmidi.cc b/libs/backends/alsa/alsa_rawmidi.cc
index 377cff4f47..035860c259 100644
--- a/libs/backends/alsa/alsa_rawmidi.cc
+++ b/libs/backends/alsa/alsa_rawmidi.cc
@@ -337,6 +337,7 @@ retry:
 AlsaRawMidiIn::AlsaRawMidiIn (const char *device)
 		: AlsaRawMidiIO (device, true)
 		, _event(0,0)
+		, _first_time(true)
 		, _unbuffered_bytes(0)
 		, _total_bytes(0)
 		, _expected_bytes(0)
@@ -471,6 +472,9 @@ int
 AlsaRawMidiIn::queue_event (const uint64_t time, const uint8_t *data, const size_t size) {
 	const uint32_t  buf_size = sizeof(MidiEventHeader) + size;
 	_event._pending = false;
+	if (size == 0) {
+		return -1;
+	}
 	if (_rb->write_space() < buf_size) {
 		_DEBUGPRINT("AlsaRawMidiIn: ring buffer overflow\n");
 		return -1;
@@ -489,6 +493,10 @@ AlsaRawMidiIn::parse_events (const uint64_t time, const uint8_t *data, const siz
 		}
 	}
 	for (size_t i = 0; i < size; ++i) {
+		if (_first_time && !(data[i] & 0x80)) {
+			continue;
+		}
+		_first_time = false; /// TODO optimize e.g. use fn pointer to different parse_events()
 		if (process_byte(time, data[i])) {
 			if (queue_event (_event._time, _parser_buffer, _event._size)) {
 				return;
diff --git a/libs/backends/alsa/alsa_rawmidi.h b/libs/backends/alsa/alsa_rawmidi.h
index 9353b92a2f..eafdf07561 100644
--- a/libs/backends/alsa/alsa_rawmidi.h
+++ b/libs/backends/alsa/alsa_rawmidi.h
@@ -143,6 +143,7 @@ private:
 		}
 	} _event;
 
+	bool    _first_time;
 	size_t  _unbuffered_bytes;
 	size_t  _total_bytes;
 	size_t  _expected_bytes;