ardour/libs/ardour/session_midi.cc

/*
  Copyright (C) 1999-2002 Paul Davis 

  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 <string>
#include <cmath>
#include <cerrno>
#include <cassert>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>

#include <boost/shared_ptr.hpp>

#include <midi++/mmc.h>
#include <midi++/port.h>
#include <midi++/manager.h>
#include <pbd/error.h>
#include <glibmm/thread.h>
#include <pbd/pthread_utils.h>

#include <ardour/configuration.h>
#include <ardour/audioengine.h>
#include <ardour/session.h>
#include <ardour/audio_track.h>
#include <ardour/midi_track.h>
#include <ardour/audio_diskstream.h>
#include <ardour/slave.h>
#include <ardour/cycles.h>
#include <ardour/smpte.h>

#include "i18n.h"

using namespace std;
using namespace ARDOUR;
using namespace PBD;
using namespace MIDI;

MachineControl::CommandSignature MMC_CommandSignature;
MachineControl::ResponseSignature MMC_ResponseSignature;


void
Session::midi_panic()
{
	{
		boost::shared_ptr<RouteList> r = routes.reader ();

		for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
			MidiTrack *track = dynamic_cast<MidiTrack*>((*i).get());
			if (track != 0) {
				track->midi_panic();
			}
		}
	}
}

int
Session::use_config_midi_ports ()
{
	string port_name;

	if (default_mmc_port) {
		set_mmc_port (default_mmc_port->name());
	} else {
		set_mmc_port ("");
	}

	if (default_mtc_port) {
		set_mtc_port (default_mtc_port->name());
	} else {
		set_mtc_port ("");
	}

	if (default_midi_port) {
		set_midi_port (default_midi_port->name());
	} else {
		set_midi_port ("");
	}

	return 0;
}	


/***********************************************************************
 MTC, MMC, etc.
**********************************************************************/

int
Session::set_mtc_port (string port_tag)
{
	MTC_Slave *ms;

	if (port_tag.length() == 0) {

		if (_slave && ((ms = dynamic_cast<MTC_Slave*> (_slave)) != 0)) {
			error << _("Ardour is slaved to MTC - port cannot be reset") << endmsg;
			return -1;
		}

		if (_mtc_port == 0) {
			return 0;
		}

		_mtc_port = 0;
		goto out;
	}

	MIDI::Port* port;

	if ((port = MIDI::Manager::instance()->port (port_tag)) == 0) {
		error << string_compose (_("unknown port %1 requested for MTC"), port_tag) << endl;
		return -1;
	}

	_mtc_port = port;

	if (_slave && ((ms = dynamic_cast<MTC_Slave*> (_slave)) != 0)) {
		ms->rebind (*port);
	}

	Config->set_mtc_port_name (port_tag);

  out:
	MTC_PortChanged(); /* EMIT SIGNAL */
	change_midi_ports ();
	set_dirty();
	return 0;
}

void
Session::set_mmc_receive_device_id (uint32_t device_id)
{
	if (mmc) {
		mmc->set_receive_device_id (device_id);
	}
}

void
Session::set_mmc_send_device_id (uint32_t device_id)
{
	if (mmc) {
		mmc->set_send_device_id (device_id);
	}
}

int
Session::set_mmc_port (string port_tag)
{
	MIDI::byte old_recv_device_id = 0;
	MIDI::byte old_send_device_id = 0;
	bool reset_id = false;

	if (port_tag.length() == 0) {
		if (_mmc_port == 0) {
			return 0;
		}
		_mmc_port = 0;
		goto out;
	}

	MIDI::Port* port;

	if ((port = MIDI::Manager::instance()->port (port_tag)) == 0) {
		return -1;
	}

	_mmc_port = port;

	if (mmc) {
		old_recv_device_id = mmc->receive_device_id();
		old_recv_device_id = mmc->send_device_id();
		reset_id = true;
		delete mmc;
	}

	mmc = new MIDI::MachineControl (*_mmc_port, 1.0, 
					MMC_CommandSignature,
					MMC_ResponseSignature);

	if (reset_id) {
		mmc->set_receive_device_id (old_recv_device_id);
		mmc->set_send_device_id (old_send_device_id);
	}

	mmc->Play.connect 
		(mem_fun (*this, &Session::mmc_deferred_play));
	mmc->DeferredPlay.connect 
		(mem_fun (*this, &Session::mmc_deferred_play));
	mmc->Stop.connect 
		(mem_fun (*this, &Session::mmc_stop));
	mmc->FastForward.connect 
		(mem_fun (*this, &Session::mmc_fast_forward));
	mmc->Rewind.connect 
		(mem_fun (*this, &Session::mmc_rewind));
	mmc->Pause.connect 
		(mem_fun (*this, &Session::mmc_pause));
	mmc->RecordPause.connect 
		(mem_fun (*this, &Session::mmc_record_pause));
	mmc->RecordStrobe.connect 
		(mem_fun (*this, &Session::mmc_record_strobe));
	mmc->RecordExit.connect 
		(mem_fun (*this, &Session::mmc_record_exit));
	mmc->Locate.connect 
		(mem_fun (*this, &Session::mmc_locate));
	mmc->Step.connect 
		(mem_fun (*this, &Session::mmc_step));
	mmc->Shuttle.connect 
		(mem_fun (*this, &Session::mmc_shuttle));
	mmc->TrackRecordStatusChange.connect
		(mem_fun (*this, &Session::mmc_record_enable));


	/* also handle MIDI SPP because its so common */

	_mmc_port->input()->start.connect (mem_fun (*this, &Session::spp_start));
	_mmc_port->input()->contineu.connect (mem_fun (*this, &Session::spp_continue));
	_mmc_port->input()->stop.connect (mem_fun (*this, &Session::spp_stop));
	
	Config->set_mmc_port_name (port_tag);

  out:
	MMC_PortChanged(); /* EMIT SIGNAL */
	change_midi_ports ();
	set_dirty();
	return 0;
}

int
Session::set_midi_port (string port_tag)
{
#if 0
	if (port_tag.length() == 0) {
		if (_midi_port == 0) {
			return 0;
		}
		_midi_port = 0;
		goto out;
	}

	MIDI::Port* port;

	if ((port = MIDI::Manager::instance()->port (port_tag)) == 0) {
		return -1;
	}

	_midi_port = port;
	
	/* XXX need something to forward this to control protocols ? or just
	   use the signal below 
	*/

	Config->set_midi_port_name (port_tag);

  out:
#endif
	MIDI_PortChanged(); /* EMIT SIGNAL */
	change_midi_ports ();
	set_dirty();
	return 0;
}

void
Session::set_trace_midi_input (bool yn, MIDI::Port* port)
{
	MIDI::Parser* input_parser;

	if (port) {
		if ((input_parser = port->input()) != 0) {
			input_parser->trace (yn, &cout, "input: ");
		}
	} else {

		if (_mmc_port) {
			if ((input_parser = _mmc_port->input()) != 0) {
				input_parser->trace (yn, &cout, "input: ");
			}
		}
		
		if (_mtc_port && _mtc_port != _mmc_port) {
			if ((input_parser = _mtc_port->input()) != 0) {
				input_parser->trace (yn, &cout, "input: ");
			}
		}

		if (_midi_port && _midi_port != _mmc_port && _midi_port != _mtc_port  ) {
			if ((input_parser = _midi_port->input()) != 0) {
				input_parser->trace (yn, &cout, "input: ");
			}
		}
	}

	Config->set_trace_midi_input (yn);
}

void
Session::set_trace_midi_output (bool yn, MIDI::Port* port)
{
	MIDI::Parser* output_parser;

	if (port) {
		if ((output_parser = port->output()) != 0) {
			output_parser->trace (yn, &cout, "output: ");
		}
	} else {
		if (_mmc_port) {
			if ((output_parser = _mmc_port->output()) != 0) {
				output_parser->trace (yn, &cout, "output: ");
			}
		}
		
		if (_mtc_port && _mtc_port != _mmc_port) {
			if ((output_parser = _mtc_port->output()) != 0) {
				output_parser->trace (yn, &cout, "output: ");
			}
		}

		if (_midi_port && _midi_port != _mmc_port && _midi_port != _mtc_port  ) {
			if ((output_parser = _midi_port->output()) != 0) {
				output_parser->trace (yn, &cout, "output: ");
			}
		}

	}

	Config->set_trace_midi_output (yn);
}

bool
Session::get_trace_midi_input(MIDI::Port *port)
{
	MIDI::Parser* input_parser;
	if (port) {
		if ((input_parser = port->input()) != 0) {
			return input_parser->tracing();
		}
	}
	else {
		if (_mmc_port) {
			if ((input_parser = _mmc_port->input()) != 0) {
				return input_parser->tracing();
			}
		}
		
		if (_mtc_port) {
			if ((input_parser = _mtc_port->input()) != 0) {
				return input_parser->tracing();
			}
		}

		if (_midi_port) {
			if ((input_parser = _midi_port->input()) != 0) {
				return input_parser->tracing();
			}
		}
	}

	return false;
}

bool
Session::get_trace_midi_output(MIDI::Port *port)
{
	MIDI::Parser* output_parser;
	if (port) {
		if ((output_parser = port->output()) != 0) {
			return output_parser->tracing();
		}
	}
	else {
		if (_mmc_port) {
			if ((output_parser = _mmc_port->output()) != 0) {
				return output_parser->tracing();
			}
		}
		
		if (_mtc_port) {
			if ((output_parser = _mtc_port->output()) != 0) {
				return output_parser->tracing();
			}
		}

		if (_midi_port) {
			if ((output_parser = _midi_port->output()) != 0) {
				return output_parser->tracing();
			}
		}
	}

	return false;

}

void
Session::setup_midi_control ()
{
	outbound_mtc_smpte_frame = 0;
	next_quarter_frame_to_send = 0;

	/* setup the MMC buffer */
	
	mmc_buffer[0] = 0xf0; // SysEx
	mmc_buffer[1] = 0x7f; // Real Time SysEx ID for MMC
	mmc_buffer[2] = (mmc ? mmc->send_device_id() : 0x7f);
	mmc_buffer[3] = 0x6;  // MCC

	/* Set up the qtr frame message */
	
	mtc_msg[0] = 0xf1;
	mtc_msg[2] = 0xf1;
	mtc_msg[4] = 0xf1;
	mtc_msg[6] = 0xf1;
	mtc_msg[8] = 0xf1;
	mtc_msg[10] = 0xf1;
	mtc_msg[12] = 0xf1;
	mtc_msg[14] = 0xf1;
}

void
Session::spp_start (Parser& ignored)
{
	if (Config->get_mmc_control() && (Config->get_slave_source() != MTC)) {
		request_transport_speed (1.0);
	}
}

void
Session::spp_continue (Parser& ignored)
{
	spp_start (ignored);
}

void
Session::spp_stop (Parser& ignored)
{
	if (Config->get_mmc_control()) {
		request_stop ();
	}
}

void
Session::mmc_deferred_play (MIDI::MachineControl &mmc)
{
	if (Config->get_mmc_control() && (Config->get_slave_source() != MTC)) {
		request_transport_speed (1.0);
	}
}

void
Session::mmc_record_pause (MIDI::MachineControl &mmc)
{
	if (Config->get_mmc_control()) {
		maybe_enable_record();
	}
}

void
Session::mmc_record_strobe (MIDI::MachineControl &mmc)
{
	if (!Config->get_mmc_control()) 
		return;

	/* record strobe does an implicit "Play" command */

	if (_transport_speed != 1.0) {

		/* start_transport() will move from Enabled->Recording, so we
		   don't need to do anything here except enable recording.
		   its not the same as maybe_enable_record() though, because
		   that *can* switch to Recording, which we do not want.
		*/
		
		save_state ("", true);
		g_atomic_int_set (&_record_status, Enabled);
		RecordStateChanged (); /* EMIT SIGNAL */
		
		request_transport_speed (1.0);

	} else {

		enable_record ();
	}
}

void
Session::mmc_record_exit (MIDI::MachineControl &mmc)
{
	if (Config->get_mmc_control()) {
		disable_record (false);
	}
}

void
Session::mmc_stop (MIDI::MachineControl &mmc)
{
	if (Config->get_mmc_control()) {
		request_stop ();
	}
}

void
Session::mmc_pause (MIDI::MachineControl &mmc)
{
	if (Config->get_mmc_control()) {

		/* We support RECORD_PAUSE, so the spec says that
		   we must interpret PAUSE like RECORD_PAUSE if
		   recording.
		*/

		if (actively_recording()) {
			maybe_enable_record ();
		} else {
			request_stop ();
		}
	}
}

static bool step_queued = false;

void
Session::mmc_step (MIDI::MachineControl &mmc, int steps)
{
	if (!Config->get_mmc_control()) {
		return;
	}

	struct timeval now;
	struct timeval diff = { 0, 0 };

	gettimeofday (&now, 0);
	
	timersub (&now, &last_mmc_step, &diff);

	gettimeofday (&now, 0);
	timersub (&now, &last_mmc_step, &diff);

	if (last_mmc_step.tv_sec != 0 && (diff.tv_usec + (diff.tv_sec * 1000000)) < _engine.usecs_per_cycle()) {
		return;
	}
	
	double diff_secs = diff.tv_sec + (diff.tv_usec / 1000000.0);
	double cur_speed = (((steps * 0.5) * smpte_frames_per_second()) / diff_secs) / smpte_frames_per_second();
	
	if (_transport_speed == 0 || cur_speed * _transport_speed < 0) {
		/* change direction */
		step_speed = cur_speed;
	} else {
		step_speed = (0.6 * step_speed) + (0.4 * cur_speed);
	}

	step_speed *= 0.25;

#if 0
	cerr << "delta = " << diff_secs 
	     << " ct = " << _transport_speed
	     << " steps = " << steps
	     << " new speed = " << cur_speed 
	     << " speed = " << step_speed
	     << endl;
#endif	

	request_transport_speed (step_speed);
	last_mmc_step = now;

	if (!step_queued) {
		midi_timeouts.push_back (mem_fun (*this, &Session::mmc_step_timeout));
		step_queued = true;
	}
}

void
Session::mmc_rewind (MIDI::MachineControl &mmc)
{
	if (Config->get_mmc_control()) {
		request_transport_speed(-8.0f);
	}
}

void
Session::mmc_fast_forward (MIDI::MachineControl &mmc)
{
	if (Config->get_mmc_control()) {
		request_transport_speed(8.0f);
	}
}

void
Session::mmc_locate (MIDI::MachineControl &mmc, const MIDI::byte* mmc_tc)
{
	if (!Config->get_mmc_control()) {
		return;
	}

	nframes_t target_frame;
	SMPTE::Time smpte;

	smpte.hours = mmc_tc[0] & 0xf;
	smpte.minutes = mmc_tc[1];
	smpte.seconds = mmc_tc[2];
	smpte.frames = mmc_tc[3];
	smpte.rate = smpte_frames_per_second();
	smpte.drop = smpte_drop_frames();
  
	// Also takes smpte offset into account:
	smpte_to_sample( smpte, target_frame, true /* use_offset */, false /* use_subframes */ );
	
	if (target_frame > max_frames) {
		target_frame = max_frames;
	}

	/* Some (all?) MTC/MMC devices do not send a full MTC frame
	   at the end of a locate, instead sending only an MMC
	   locate command. This causes the current position
	   of an MTC slave to become out of date. Catch this.
	*/

	MTC_Slave* mtcs = dynamic_cast<MTC_Slave*> (_slave);

	if (mtcs != 0) {
		// cerr << "Locate *with* MTC slave\n";
		mtcs->handle_locate (mmc_tc);
	} else {
		// cerr << "Locate without MTC slave\n";
		request_locate (target_frame, false);
	}
}

void
Session::mmc_shuttle (MIDI::MachineControl &mmc, float speed, bool forw)
{
	if (!Config->get_mmc_control()) {
		return;
	}

	if (Config->get_shuttle_speed_threshold() >= 0 && speed > Config->get_shuttle_speed_threshold()) {
		speed *= Config->get_shuttle_speed_factor();
	}

	if (forw) {
		request_transport_speed (speed);
	} else {
		request_transport_speed (-speed);
	}
}

void
Session::mmc_record_enable (MIDI::MachineControl &mmc, size_t trk, bool enabled)
{
	if (Config->get_mmc_control()) {

		RouteList::iterator i;
		boost::shared_ptr<RouteList> r = routes.reader();
		
		for (i = r->begin(); i != r->end(); ++i) {
			AudioTrack *at;

			if ((at = dynamic_cast<AudioTrack*>((*i).get())) != 0) {
				if (trk == at->remote_control_id()) {
					at->set_record_enable (enabled, &mmc);
					break;
				}
			}
		}
	}
}

void
Session::change_midi_ports ()
{
	MIDIRequest* request = new MIDIRequest;

	request->type = MIDIRequest::PortChange;
	midi_requests.write (&request, 1);
	poke_midi_thread ();
}

/** Send MTC Full Frame message (complete SMPTE time) for the start of this cycle.
 * This resets the MTC code, the next quarter frame message that is sent will be
 * the first one with the beginning of this cycle as the new start point.
 */

int
Session::send_full_time_code(nframes_t nframes)
{
	/* This function could easily send at a given frame offset, but would
	 * that be useful?  Does ardour do sub-block accurate locating? [DR] */

	MIDI::byte msg[10];
	SMPTE::Time smpte;

	_send_smpte_update = false;

	if (_mtc_port == 0 || !session_send_mtc) {
		return 0;
	}
	
	// Get smpte time for this transport frame
	sample_to_smpte(_transport_frame, smpte, true /* use_offset */, false /* no subframes */);

	transmitting_smpte_time = smpte;
	outbound_mtc_smpte_frame = _transport_frame;

	// I don't understand this bit yet.. [DR]
	if (((mtc_smpte_bits >> 5) != MIDI::MTC_25_FPS) && (transmitting_smpte_time.frames % 2)) {
		// start MTC quarter frame transmission on an even frame
		SMPTE::increment( transmitting_smpte_time );
		outbound_mtc_smpte_frame += (nframes_t) _frames_per_smpte_frame;
	}

	// Compensate for audio latency
	outbound_mtc_smpte_frame += _worst_output_latency;

	next_quarter_frame_to_send = 0;

	// Sync slave to the same SMPTE time as we are on
	msg[0] = 0xf0;
	msg[1] = 0x7f;
	msg[2] = 0x7f;
	msg[3] = 0x1;
	msg[4] = 0x1;
	msg[9] = 0xf7;

	msg[5] = mtc_smpte_bits | smpte.hours;
	msg[6] = smpte.minutes;
	msg[7] = smpte.seconds;
	msg[8] = smpte.frames;

	cerr << "MTC: Sending full time code at " << outbound_mtc_smpte_frame << endl;

	// Send message at offset 0, sent time is for the start of this cycle
	if (_mtc_port->midimsg (msg, sizeof (msg), 0)) {
		error << _("Session: could not send full MIDI time code") << endmsg;
		return -1;
	}

	return 0;
}


/** Sends MTC (quarter-frame) messages for this cycle.
 * Must be called exactly once per cycle from the audio thread.  Realtime safe.
 * This function assumes the state of full SMPTE is sane, eg. the slave is
 * expecting quarter frame messages and has the right frame of reference (any
 * full MTC SMPTE time messages that needed to be sent should have been sent
 * earlier already this cycle by send_full_time_code)
 */
int
Session::send_midi_time_code_for_cycle(nframes_t nframes)
{	
	assert (next_quarter_frame_to_send >= 0);
	assert (next_quarter_frame_to_send <= 7);
	
	if (_mtc_port == 0 || !session_send_mtc || transmitting_smpte_time.negative
	    /*|| (next_quarter_frame_to_send < 0)*/ ) {
		// cerr << "(MTC) Not sending MTC\n";
		return 0;
	}
	
	/* Duration of one quarter frame */
	nframes_t quarter_frame_duration = ((long) _frames_per_smpte_frame) >> 2;
	
	// cerr << "(MTC) TR: " << _transport_frame << " - SF: " << outbound_mtc_smpte_frame
	// << " - NQ: " << next_quarter_frame_to_send << " - FD" << quarter_frame_duration << endl;
		
	// FIXME: this should always be true
	//assert((outbound_mtc_smpte_frame + (next_quarter_frame_to_send * quarter_frame_duration))
	//		> _transport_frame);

	
	// Send quarter frames for this cycle
	while (_transport_frame + nframes > (outbound_mtc_smpte_frame +
				(next_quarter_frame_to_send * quarter_frame_duration))) {
		
		// cerr << "(MTC) Next frame to send: " << next_quarter_frame_to_send << endl;

		switch (next_quarter_frame_to_send) {
			case 0:
				mtc_msg[1] =  0x00 | (transmitting_smpte_time.frames & 0xf);
				break;
			case 1:
				mtc_msg[1] =  0x10 | ((transmitting_smpte_time.frames & 0xf0) >> 4);
				break;
			case 2:
				mtc_msg[1] =  0x20 | (transmitting_smpte_time.seconds & 0xf);
				break;
			case 3:
				mtc_msg[1] =  0x30 | ((transmitting_smpte_time.seconds & 0xf0) >> 4);
				break;
			case 4:
				mtc_msg[1] =  0x40 | (transmitting_smpte_time.minutes & 0xf);
				break;
			case 5:
				mtc_msg[1] = 0x50 | ((transmitting_smpte_time.minutes & 0xf0) >> 4);
				break;
			case 6:
				mtc_msg[1] = 0x60 | ((mtc_smpte_bits|transmitting_smpte_time.hours) & 0xf);
				break;
			case 7:
				mtc_msg[1] = 0x70 | (((mtc_smpte_bits|transmitting_smpte_time.hours) & 0xf0) >> 4);
				break;
		}			
		
		const nframes_t msg_time = (outbound_mtc_smpte_frame
			+ (quarter_frame_duration * next_quarter_frame_to_send));
	
		// This message must fall within this block or something is broken
		assert(msg_time >= _transport_frame);
		assert(msg_time < _transport_frame + nframes);

		nframes_t out_stamp = msg_time - _transport_frame;
		assert(out_stamp < nframes);

		if (_mtc_port->midimsg (mtc_msg, 2, out_stamp)) {
			error << string_compose(_("Session: cannot send quarter-frame MTC message (%1)"), strerror (errno)) 
			      << endmsg;
			return -1;
		}

		/*cerr << "(MTC) SMPTE: " << transmitting_smpte_time.hours
			<< ":" << transmitting_smpte_time.minutes
			<< ":" << transmitting_smpte_time.seconds
			<< ":" << transmitting_smpte_time.frames
			<< ", qfm = " << next_quarter_frame_to_send
			<< ", stamp = " << out_stamp
			<< ", delta = " << _transport_frame + out_stamp - last_time << endl;*/
		
		// Increment quarter frame counter
		next_quarter_frame_to_send++;

		if (next_quarter_frame_to_send >= 8) {
			// Wrap quarter frame counter
			next_quarter_frame_to_send = 0;
			// Increment smpte time twice
			SMPTE::increment( transmitting_smpte_time );
			SMPTE::increment( transmitting_smpte_time );        
			// Re-calculate timing of first quarter frame
			//smpte_to_sample( transmitting_smpte_time, outbound_mtc_smpte_frame, true /* use_offset */, false );
			outbound_mtc_smpte_frame += 8 * quarter_frame_duration;
			// Compensate for audio latency
			outbound_mtc_smpte_frame += _worst_output_latency;
		}
	}

	return 0;
}

/***********************************************************************
 OUTBOUND MMC STUFF
**********************************************************************/

void
Session::deliver_mmc (MIDI::MachineControl::Command cmd, nframes_t where)
{
	using namespace MIDI;
	int nbytes = 4;
	SMPTE::Time smpte;

	if (_mmc_port == 0 || !session_send_mmc) {
		// cerr << "Not delivering MMC " << _mmc_port << " - " << session_send_mmc << endl;
		return;
	}

	mmc_buffer[nbytes++] = cmd;

	// cerr << "delivering MMC, cmd = " << hex << (int) cmd << dec << endl;
	
	switch (cmd) {
	case MachineControl::cmdLocate:
		smpte_time_subframes (where, smpte);

		mmc_buffer[nbytes++] = 0x6; // byte count
		mmc_buffer[nbytes++] = 0x1; // "TARGET" subcommand
		mmc_buffer[nbytes++] = smpte.hours;
		mmc_buffer[nbytes++] = smpte.minutes;
		mmc_buffer[nbytes++] = smpte.seconds;
		mmc_buffer[nbytes++] = smpte.frames;
		mmc_buffer[nbytes++] = smpte.subframes;
		break;

	case MachineControl::cmdStop:
		break;

	case MachineControl::cmdPlay:
		/* always convert Play into Deferred Play */
		/* Why? [DR] */
		mmc_buffer[4] = MachineControl::cmdDeferredPlay;
		break;

	case MachineControl::cmdDeferredPlay:
		break;

	case MachineControl::cmdRecordStrobe:
		break;

	case MachineControl::cmdRecordExit:
		break;

	case MachineControl::cmdRecordPause:
		break;

	default:
		nbytes = 0;
	};

	if (nbytes) {

		mmc_buffer[nbytes++] = 0xf7; // terminate SysEx/MMC message

		if (_mmc_port->midimsg (mmc_buffer, nbytes, 0)) {
			error << string_compose(_("MMC: cannot send command %1%2%3"), &hex, cmd, &dec) << endmsg;
		} 
	}
}

bool
Session::mmc_step_timeout ()
{
	struct timeval now;
	struct timeval diff;
	double diff_usecs;
	gettimeofday (&now, 0);

	timersub (&now, &last_mmc_step, &diff);
	diff_usecs = diff.tv_sec * 1000000 + diff.tv_usec;

	if (diff_usecs > 1000000.0 || fabs (_transport_speed) < 0.0000001) {
		/* too long or too slow, stop transport */
		request_transport_speed (0.0);
		step_queued = false;
		return false;
	}

	if (diff_usecs < 250000.0) {
		/* too short, just keep going */
		return true;
	}

	/* slow it down */

	request_transport_speed (_transport_speed * 0.75);
	return true;
}

/*---------------------------------------------------------------------------
  MIDI THREAD 
  ---------------------------------------------------------------------------*/

int
Session::start_midi_thread ()
{
	if (pipe (midi_request_pipe)) {
		error << string_compose(_("Cannot create transport request signal pipe (%1)"), strerror (errno)) << endmsg;
		return -1;
	}

	if (fcntl (midi_request_pipe[0], F_SETFL, O_NONBLOCK)) {
		error << string_compose(_("UI: cannot set O_NONBLOCK on "    "signal read pipe (%1)"), strerror (errno)) << endmsg;
		return -1;
	}

	if (fcntl (midi_request_pipe[1], F_SETFL, O_NONBLOCK)) {
		error << string_compose(_("UI: cannot set O_NONBLOCK on "    "signal write pipe (%1)"), strerror (errno)) << endmsg;
		return -1;
	}

	if (pthread_create_and_store ("transport", &midi_thread, 0, _midi_thread_work, this)) {
		error << _("Session: could not create transport thread") << endmsg;
		return -1;
	}

	return 0;
}

void
Session::terminate_midi_thread ()
{
	if (midi_thread) {

		MIDIRequest* request = new MIDIRequest;
		void* status;
		
		request->type = MIDIRequest::Quit;
		
		midi_requests.write (&request, 1);
		poke_midi_thread ();

		pthread_join (midi_thread, &status);
	}
}

void
Session::poke_midi_thread ()
{
	static char c = 0;

	if (write (midi_request_pipe[1], &c, 1) != 1) {
		error << string_compose(_("cannot send signal to midi thread! (%1)"), strerror (errno)) << endmsg;
	}
}

void *
Session::_midi_thread_work (void* arg)
{
	pthread_setcancelstate (PTHREAD_CANCEL_ENABLE, 0);
	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);

	((Session *) arg)->midi_thread_work ();
	return 0;
}

void
Session::midi_thread_work ()
{
	MIDIRequest* request;
	struct pollfd pfd[4];
	int nfds = 0;
	int timeout;
	int fds_ready;
	struct sched_param rtparam;
	int x;
	bool restart;
	vector<MIDI::Port*> ports;

	PBD::ThreadCreatedWithRequestSize (pthread_self(), X_("MIDI"), 2048);

	memset (&rtparam, 0, sizeof (rtparam));
	rtparam.sched_priority = 9; /* XXX should be relative to audio (JACK) thread */
	
	if ((x = pthread_setschedparam (pthread_self(), SCHED_FIFO, &rtparam)) != 0) {
		// do we care? not particularly.
	} 

	/* set up the port vector; 4 is the largest possible size for now */

	ports.assign (4, (MIDI::Port*) 0);

	while (1) {

		nfds = 0;

		pfd[nfds].fd = midi_request_pipe[0];
		pfd[nfds].events = POLLIN|POLLHUP|POLLERR;
		nfds++;

		if (Config->get_mmc_control() && _mmc_port && _mmc_port->selectable() >= 0) {
			pfd[nfds].fd = _mmc_port->selectable();
			pfd[nfds].events = POLLIN|POLLHUP|POLLERR;
			ports[nfds] = _mmc_port;
			nfds++;
		}

		/* if MTC is being handled on a different port from MMC
		   or we are not handling MMC at all, poll
		   the relevant port.
		*/

		if (_mtc_port && (_mtc_port != _mmc_port || !Config->get_mmc_control()) && _mtc_port->selectable() >= 0) {
			pfd[nfds].fd = _mtc_port->selectable();
			pfd[nfds].events = POLLIN|POLLHUP|POLLERR;
			ports[nfds] = _mtc_port;
			nfds++;
		}

		/* if we are using MMC control, we obviously have to listen
		   the relevant port.
		*/

		if (_midi_port && (_midi_port != _mmc_port || !Config->get_mmc_control()) && (_midi_port != _mtc_port) && _midi_port->selectable() >= 0) {
			pfd[nfds].fd = _midi_port->selectable();
			pfd[nfds].events = POLLIN|POLLHUP|POLLERR;
			ports[nfds] = _midi_port;
			nfds++;
		}
		
		if (!midi_timeouts.empty()) {
			timeout = 100; /* 10msecs */
		} else {
			timeout = -1; /* if there is no data, we don't care */
		}

	  again:
		// cerr << "MIDI poll on " << nfds << " for " << timeout << endl;
		if (poll (pfd, nfds, timeout) < 0) {
			if (errno == EINTR) {
				/* gdb at work, perhaps */
				goto again;
			}

			error << string_compose(_("MIDI thread poll failed (%1)"), strerror (errno)) << endmsg;

			break;
		}
		// cerr << "MIDI thread wakes at " << get_cycles () << endl;

		fds_ready = 0;

		/* check the transport request pipe */

		if (pfd[0].revents & ~POLLIN) {
			error << _("Error on transport thread request pipe") << endmsg;
			break;
		}

		if (pfd[0].revents & POLLIN) {

			char foo[16];
			
			// cerr << "MIDI request FIFO ready\n";
			fds_ready++;

			/* empty the pipe of all current requests */

			while (1) {
				size_t nread = read (midi_request_pipe[0], &foo, sizeof (foo));

				if (nread > 0) {
					if ((size_t) nread < sizeof (foo)) {
						break;
					} else {
						continue;
					}
				} else if (nread == 0) {
					break;
				} else if (errno == EAGAIN) {
					break;
				} else {
					fatal << _("Error reading from transport request pipe") << endmsg;
					/*NOTREACHED*/
				}
			}

			while (midi_requests.read (&request, 1) == 1) {

				switch (request->type) {
				case MIDIRequest::PortChange:
					/* restart poll with new ports */
					// cerr << "rebind\n";
					restart = true;
					break;
						
				case MIDIRequest::Quit:
					delete request;
					pthread_exit_pbd (0);
					/*NOTREACHED*/
					break;
					
				default:
					break;
				}


				delete request;
			}

		} 

		if (restart) {
			continue;
		}

		/* now read the rest of the ports */

		for (int p = 1; p < nfds; ++p) {
			if ((pfd[p].revents & ~POLLIN)) {
				// error << string_compose(_("Transport: error polling MIDI port %1 (revents =%2%3%4"), p, &hex, pfd[p].revents, &dec) << endmsg;
				break;
			}
			
			if (pfd[p].revents & POLLIN) {
				fds_ready++;
				ports[p]->parse ();
			}
		}

		/* timeout driven */
		
		if (fds_ready < 2 && timeout != -1) {

			for (MidiTimeoutList::iterator i = midi_timeouts.begin(); i != midi_timeouts.end(); ) {
				
				MidiTimeoutList::iterator tmp;
				tmp = i;
				++tmp;
				
				if (!(*i)()) {
					midi_timeouts.erase (i);
				}
				
				i = tmp;
			}
		}
	}
}