MidiTrack.cpp

// -*- mode: c++; coding: utf-8 -*-

// Linthesia

// Copyright (c) 2007 Nicholas Piegdon
// Adaptation to GNU/Linux by Oscar Aceña
// See COPYING for license information

#include "MidiTrack.h"
#include "MidiEvent.h"
#include "MidiUtil.h"
#include "Midi.h"

#include <stdint.h>
#include <sstream>
#include <string>
#include <map>

using namespace std;

MidiTrack MidiTrack::ReadFromStream(std::istream &stream) {
  // Verify the track header
  const static string MidiTrackHeader = "MTrk";

  // I could use (MidiTrackHeader.length() + 1), but then this has to be
  // dynamically allocated.  More hassle than it's worth.  MIDI is well
  // defined and will always have a 4-byte header.  We use 5 so we get
  // free null termination.
  char header_id[5] = { 0, 0, 0, 0, 0 };
  uint32_t track_length;

  stream.read(header_id, static_cast<streamsize>(MidiTrackHeader.length()));
  stream.read(reinterpret_cast<char*>(&track_length), sizeof(uint32_t));

  if (stream.fail())
    throw MidiError(MidiError_TrackHeaderTooShort);

  string header(header_id);
  if (header != MidiTrackHeader)
    throw MidiError_BadTrackHeaderType;

  // Pull the full track out of the file all at once -- there is an
  // End-Of-Track event, but this allows us handle malformed MIDI a
  // little more gracefully.
  track_length = BigToSystem32(track_length);
  char *buffer = new char[track_length + 1];
  buffer[track_length] = 0;

  stream.read(buffer, track_length);
  if (stream.fail()) {
    delete[] buffer;
    throw MidiError(MidiError_TrackTooShort);
  }

  // We have to jump through a couple hoops because istringstream
  // can't handle binary data unless constructed through an std::string.
  string buffer_string(buffer, track_length);
  istringstream event_stream(buffer_string, ios::binary);
  delete[] buffer;

  MidiTrack t;

  // Read events until we run out of track
  char last_status = 0;
  unsigned long current_pulse_count = 0;
  while (event_stream.peek() != char_traits<char>::eof()) {
    MidiEvent ev = MidiEvent::ReadFromStream(event_stream, last_status);
    last_status = ev.StatusCode();

    t.m_events.push_back(ev);

    current_pulse_count += ev.GetDeltaPulses();
    t.m_event_pulses.push_back(current_pulse_count);
  }

  t.BuildNoteSet();
  t.DiscoverInstrument();

  return t;
}

struct NoteInfo {

   int velocity;
   unsigned char channel;
   unsigned long pulses;
};

void MidiTrack::BuildNoteSet() {
  m_note_set.clear();

  // Keep a list of all the notes currently "on" (and the pulse that
  // it was started).  On a note_on event, we create an element.  On
  // a note_off event we check that an element exists, make a "Note",
  // and remove the element from the list.  If there is already an
  // element on a note_on we both cap off the previous "Note" and
  // begin a new one.
  //
  // A note_on with velocity 0 is a note_off
  map<NoteId, NoteInfo> m_active_notes;

  for (size_t i = 0; i < m_events.size(); ++i) {
    const MidiEvent &ev = m_events[i];
    if (ev.Type() != MidiEventType_NoteOn && ev.Type() != MidiEventType_NoteOff)
      continue;

    bool on = (ev.Type() == MidiEventType_NoteOn && ev.NoteVelocity() > 0);
    NoteId id = ev.NoteNumber();

    // Check for an active note
    map<NoteId, NoteInfo>::iterator find_ret = m_active_notes.find(id);
    bool active_event = (find_ret !=  m_active_notes.end());

    // Close off the last event if there was one
    if (active_event) {
      Note n;
      n.start = find_ret->second.pulses;
      n.end = m_event_pulses[i];
      n.note_id = id;
      n.channel = find_ret->second.channel;
      n.velocity = find_ret->second.velocity;

      // NOTE: This must be set at the next level up.  The track
      // itself has no idea what its index is.
      n.track_id = 0;

      // Add a note and remove this NoteId from the active list
      m_note_set.insert(n);
      m_active_notes.erase(find_ret);
    }

    // We've handled any active events.  If this was a note_off we're done.
    if (!on)
      continue;

    // Add a new active event
    NoteInfo info;
    info.channel = ev.Channel();
    info.velocity = ev.NoteVelocity();
    info.pulses = m_event_pulses[i];

    m_active_notes[id] = info;
  }

  if (m_active_notes.size() > 0) {
    // LOGTODO!

    // This is mostly non-critical.
    //
    // Erroring out would be needlessly restrictive against
    // promiscuous MIDI files.  As-is, a note just won't be
    // inserted if it isn't closed properly.
  }
}

void MidiTrack::DiscoverInstrument() {
  // Default to Program 0 per the MIDI Standard
  m_instrument_id = 0;
  bool instrument_found = false;

  // These are actually 10 and 16 in the MIDI standard.  However, MIDI
  // channels are 1-based facing the user.  They're stored 0-based.
  const static int PercussionChannel1 = 9;
  const static int PercussionChannel2 = 15;

  // Check to see if any/all of the notes
  // in this track use Channel 10.
  bool any_note_uses_percussion = false;
  bool any_note_does_not_use_percussion = false;

  for (size_t i = 0; i < m_events.size(); ++i) {
    const MidiEvent &ev = m_events[i];

    if (ev.Type() != MidiEventType_NoteOn)
      continue;

    if (ev.Channel() == PercussionChannel1 || ev.Channel() == PercussionChannel2)
      any_note_uses_percussion = true;

    if (ev.Channel() != PercussionChannel1 && ev.Channel() != PercussionChannel2)
      any_note_does_not_use_percussion = true;
  }

  if (any_note_uses_percussion && !any_note_does_not_use_percussion) {
    m_instrument_id = InstrumentIdPercussion;
    return;
  }

  if (any_note_uses_percussion && any_note_does_not_use_percussion) {
    m_instrument_id = InstrumentIdVarious;
    return;
  }

  for (size_t i = 0; i < m_events.size(); ++i) {
    const MidiEvent &ev = m_events[i];

    if (ev.Type() != MidiEventType_ProgramChange)
      continue;

    // If we've already hit a different instrument in this
    // same track, just tag it as "various" and exit early
    //
    // Also check that the same instrument isn't just set
    // multiple times in the same track
    if (instrument_found && m_instrument_id != ev.ProgramNumber()) {
      m_instrument_id = InstrumentIdVarious;
      return;
    }

    m_instrument_id = ev.ProgramNumber();
    instrument_found = true;
  }
}

void MidiTrack::SetTrackId(size_t track_id) {
  NoteSet old = m_note_set;

  m_note_set.clear();
  for (NoteSet::const_iterator i = old.begin(); i != old.end(); ++i) {
    Note n = *i;
    n.track_id = track_id;

    m_note_set.insert(n);
  }
}

void MidiTrack::Reset() {
  m_running_microseconds = 0;
  m_last_event = -1;

  m_notes_remaining = static_cast<unsigned int>(m_note_set.size());
}

MidiEventList MidiTrack::Update(microseconds_t delta_microseconds) {
  m_running_microseconds += delta_microseconds;

  MidiEventList evs;
  for (size_t i = m_last_event + 1; i < m_events.size(); ++i) {
    if (m_event_usecs[i] <= m_running_microseconds) {
      evs.push_back(m_events[i]);
      m_last_event = static_cast<long>(i);

      if (m_events[i].Type() == MidiEventType_NoteOn && m_events[i].NoteVelocity() > 0)
        m_notes_remaining--;
    }

    else
      break;
  }

  return evs;
}

void MidiTrack::GoTo(microseconds_t microsecond_song_position) { 
  m_running_microseconds = microsecond_song_position;
  m_last_event = -1;
  m_notes_remaining = static_cast<unsigned int>(m_note_set.size());

  for (size_t i = 0; i < m_events.size(); ++i) {
    if (m_event_usecs[i] <= m_running_microseconds) {
      m_last_event = static_cast<long>(i);

      if (m_events[i].Type() == MidiEventType_NoteOn && m_events[i].NoteVelocity() > 0)
        m_notes_remaining--;
    }

    else
      break;
  }
}