C++ Alg_seq_ptr::insert_silence方法代码示例

Alg_seq_ptr NoteTrack::MakeExportableSeq()
{
   double offset = GetOffset();
   if (offset == 0)
      return mSeq;
   // make a copy, deleting events that are shifted before time 0
   double start = -offset;
   if (start < 0) start = 0;
   // notes that begin before "start" are not included even if they
   // extend past "start" (because "all" parameter is set to false)
   Alg_seq_ptr seq = mSeq->copy(start, mSeq->get_dur() - start, false);
   if (offset > 0) {
      // swap seq and mSeq so that Shift operates on the new copy
      Alg_seq_ptr old_seq = mSeq;
      mSeq = seq;
      Shift(offset);
      seq = mSeq;  // undo the swap
      mSeq = old_seq;
#ifdef OLD_CODE
      // now shift events by offset. This must be done with an integer
      // number of measures, so first, find the beats-per-measure
      double beats_per_measure = 4.0;
      Alg_time_sig_ptr tsp = NULL;
      if (seq->time_sig.length() > 0 && seq->time_sig[0].beat < ALG_EPS) {
         // there is an initial time signature
         tsp = &(seq->time_sig[0]);
         beats_per_measure = (tsp->num * 4) / tsp->den;
      }
      // also need the initial tempo
      double bps = ALG_DEFAULT_BPM / 60;
      Alg_time_map_ptr map = seq->get_time_map();
      Alg_beat_ptr bp = &(map->beats[0]);
      if (bp->time < ALG_EPS) { // tempo change at time 0
         if (map->beats.len > 1) { // compute slope to get tempo
            bps = (map->beats[1].beat - map->beats[0].beat) /
                  (map->beats[1].time - map->beats[0].time);
         } else if (seq->get_time_map()->last_tempo_flag) {
            bps = seq->get_time_map()->last_tempo;
         }
      }
      // find closest number of measures to fit in the gap
      // number of measures is offset / measure_time
      double measure_time = beats_per_measure / bps; // seconds per measure
      int n = ROUND(offset / measure_time);
      if (n == 0) n = 1;
      // we will insert n measures. Compute the desired duration of each.
      measure_time = offset / n;
      bps = beats_per_measure / measure_time;
      // insert integer multiple of measures at beginning
      seq->convert_to_beats();
      seq->insert_silence(0, beats_per_measure * n);
      // make sure time signature at 0 is correct
      if (tsp) {
         seq->set_time_sig(0, tsp->num, tsp->den);
      }
      // adjust tempo to match offset
      seq->set_tempo(bps * 60.0, 0, beats_per_measure * n);
#endif
   } else {
      // if offset is negative, it might not be a multiple of beats, but
      // we want to preserve the relative positions of measures. I.e. we
      // should shift barlines and time signatures as well as notes.
      // Insert a time signature at the first bar-line if necessary.

      // Translate start from seconds to beats and call it beat:
      double beat = mSeq->get_time_map()->time_to_beat(start);
      // Find the time signature in mSeq in effect at start (beat):
      int i = mSeq->time_sig.find_beat(beat);
      // i is where you would insert a new time sig at beat,
      // Case 1: beat coincides with a time sig at i. Time signature
      // at beat means that there is a barline at beat, so when beat
      // is shifted to 0, the relative barline positions are preserved
      if (mSeq->time_sig.length() > 0 &&
          within(beat, mSeq->time_sig[i].beat, ALG_EPS)) {
         // beat coincides with time signature change, so offset must
         // be a multiple of beats
         /* do nothing */ ;
      // Case 2: there is no time signature before beat.
      } else if (i == 0 && (mSeq->time_sig.length() == 0 ||
                            mSeq->time_sig[i].beat > beat)) {
         // If beat does not fall on an implied barline, we need to
         // insert a time signature.
         double measures = beat / 4.0;
         double imeasures = ROUND(measures);
         if (!within(measures, imeasures, ALG_EPS)) {
            double bar_offset = (int(measures) + 1) * 4.0 - beat;
            seq->set_time_sig(bar_offset, 4, 4);
         }
      // This case should never be true because if i == 0, either there
      // are no time signatures before beat (Case 2),
      // or there is one time signature at beat (Case 1)
      } else if (i == 0) {
         /* do nothing (might be good to assert(false)) */ ;
      // Case 3: i-1 must be the effective time sig position
      } else {
         i -= 1; // index the time signature in effect at beat
         Alg_time_sig_ptr tsp = &(mSeq->time_sig[i]);
         double beats_per_measure = (tsp->num * 4) / tsp->den;
         double measures = (beat - tsp->beat) / beats_per_measure;
         int imeasures = ROUND(measures);
//.........这里部分代码省略.........