初始化内容

third/midifile/tools/stretch.cpp

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+//
+// Programmer:    Ziemowit Laski <zlaski@ziemas.net>
+// Creation Date: Sun, Jun 12, 2016 11:09:34 AM
+// Last Modified: Sun, Jun 12, 2016 11:09:34 AM
+// Filename:      tools/stretch.cpp
+// URL:           https://github.com/craigsapp/midifile/blob/master/tools/stretch.cpp
+// Syntax:        C++11
+// vim:           ts=3
+//
+// Description:   Stretches (or shrinks):
+//                1. The position of bars (measures) in tracks,
+//                   without affecting tempo, and/or
+//                2. The tempo (BPM) itself.
+//
+//                This is useful when working with MIDI files
+//                that were automatically generated from audio
+//                (MP3, WAV) files.  Conversion software often
+//                has difficulty in correct placement of
+//                bars, and also sometimes does not preserve
+//                the tempo of the original.
+//   
+
+#include "MidiFile.h"
+#include "Options.h"
+
+#include <algorithm>
+#include <cmath>
+#include <iostream>
+
+using namespace std;
+using namespace smf;
+
+
+void doStretch (MidiFile& midifile, double bars, double duration);
+
+
+///////////////////////////////////////////////////////////////////////////
+
+int main(int argc, char** argv) {
+	Options options;
+	options.define("b|bars|m|measures=d:1.0", 
+			"Stretch width of bars (measures) by factor specified (WITHOUT affecting tempo)");
+	options.define("d|duration|t|tempo=d:1.0",
+			"Stretch duration of track(s) by factor specified");
+	options.process(argc, argv);
+	if (options.getArgCount() != 2) {
+		cerr << "two MIDI filenames are required.\n";
+		exit(1);
+	}
+
+	MidiFile midifile;
+	midifile.read(options.getArg(1));
+	if (!midifile.status()) {
+		cerr << "Error reading MIDI file " << options.getArg(1) << endl;
+		exit(1);
+	}
+
+	if (options.getBoolean("bars") || options.getBoolean("duration")) {
+		double bars = options.getDouble("bars");
+		double duration = options.getDouble("duration");
+		if (bars < 0.1 || bars > 10.0 || duration < 0.1 || duration > 10.0) {
+			cerr << "stretch parameters must be between 0.1 and 10.\n";
+			exit(1);
+		}
+		doStretch(midifile, bars, duration);
+	}
+
+	midifile.write(options.getArg(2));
+	return 0;
+}
+
+
+///////////////////////////////////////////////////////////////////////////
+
+//////////////////////////////
+//
+// doStretch -- Stretch size of all bars (measures) in the file 
+//   by a specified 'bars' factor. (Values lower than 1.0 will result
+//   in shrinking).  Note that bars (measures) are not encoded in MIDI
+//   directly as an event type.  Instead, they are computed from the
+//   Pulse Per Quarter Note (PPQN) value in the file header; PPQN
+//   multiplied by the number of quarter notes in a measure (as 
+//   determined by the time signature contained in the FF 58
+//   message) gives the number of ticks in each measure. The
+//   'duration' parameter specifies the factor by which the
+//   duration of the track(s) should be stretched (or shrunk,
+//   if less than 1.0).
+
+void doStretch(MidiFile& midifile, double bars, double duration) {
+	int ppqn = midifile.getTicksPerQuarterNote();
+	int new_ppqn = max( 24576, ppqn );
+	midifile.setTicksPerQuarterNote( new_ppqn );
+	double tick_mult = (double)new_ppqn / (double)ppqn;
+	tick_mult /= bars;
+
+	for (int t = 0; t < midifile.size(); ++t) {
+		MidiEventList &track = midifile[t];
+		for (int e = 0; e < track.size(); ++e) {
+			MidiEvent &event = track[e];
+			event.tick *= (int)(event.tick * tick_mult);
+			if (event.getMetaType() == 0x51) {
+			double tempo = event.getTempoMicroseconds();
+			tempo *= bars;
+			tempo *= duration;
+			event.setTempoMicroseconds( (int)tempo );
+			}
+		}
+	}
+}
+
+
+