source: osm/applications/editors/josm/plugins/wms-turbo-challenge2/src/wmsturbochallenge/EngineSound.java@ 21477

/*
 * GPLv2 or 3, Copyright (c) 2010  Andrzej Zaborowski
 *
 * This class simulates a car engine.  What does a car engine do?  It
 * makes a pc-speaker-like buzz.  The PC Speaker could only emit
 * a (nearly) square wave and we simulate it here for maximum realism.
 */
package wmsturbochallenge;

import java.util.Timer;
import java.util.TimerTask;

import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.DataLine;
import javax.sound.sampled.SourceDataLine;
import javax.sound.sampled.AudioFormat;

class engine {
        public engine() {
                rpm = 0.0;
        }

        public void start() {
                rpm = 0.3;
                speed = 0.0;
                n = 0;

                if (output != null)
                        stop();

                AudioFormat output_format =
                        new AudioFormat(S_RATE, 16, 1, true, true);
                DataLine.Info info =
                        new DataLine.Info(SourceDataLine.class, output_format);

                /* Get the data line, open it and initialise the device */
                try {
                        output = (SourceDataLine) AudioSystem.getLine(info);
                        output.open(output_format);
                        output.start();
                        frames_written = 0;
                        reschedule(0);
                } catch (Exception e) {
                        output = null;
                        System.out.println("Audio not available: " +
                                        e.getClass().getSimpleName());
                }
        }

        public void stop() {
                rpm = 0.0;
                n = 0;

                if (output == null)
                        return;

                tick.cancel();
                tick.purge();

                output.stop();
                output.flush();
                output.close();
                output = null;
        }

        public void set_speed(double speed) {
                /* This engine is equipped with an automatic gear box that
                 * switches gears when the RPM becomes too high or too low.  */
                double new_speed = Math.abs(speed);
                double accel = new_speed - this.speed;
                this.speed = new_speed;

                if (accel > 0.05)
                        accel = 0.05;
                else if (accel < -0.05)
                        accel = -0.05;
                rpm += accel;

                if (accel > 0.0 && rpm > 1.0 + n * 0.2 && speed > 0.0) {
                        rpm = 0.3 + n * 0.2;
                        n ++;
                } else if (accel < 0.0 && rpm < 0.3) {
                        if (n > 0) {
                                rpm = 0.7 + n * 0.1;
                                n --;
                        } else
                                rpm = 0.2;
                }
                if (speed < 2.0)
                        n = 0;
        }

        public boolean is_on() {
                return output != null;
        }

        protected double speed;
        protected double rpm;
        protected int n;

        protected SourceDataLine output = null;
        protected long frames_written;
        protected Timer tick = new Timer();

        /* Audio parameters.  */
        protected static final int S_RATE = 44100;
        protected static final int MIN_BUFFER = 4096;
        protected static final double volume = 0.3;

        protected class audio_task extends TimerTask {
                public void run() {
                        if (output == null)
                                return;

                        /* If more than a two buffers left to play,
                         * reschedule and try to wake up closer to the
                         * end of already written data.  */
                        long frames_current = output.getLongFramePosition();
                        if (frames_current < frames_written - MIN_BUFFER * 2) {
                                reschedule(frames_current);
                                return;
                        }

                        /* Build a new buffer */
                        /* double freq = 20 * Math.pow(1.3, rpm * 5.0); */
                        double freq = (rpm - 0.1) * 160.0;
                        int wavelen = (int) (S_RATE / freq);
                        int bufferlen = MIN_BUFFER - (MIN_BUFFER % wavelen) +
                                wavelen;
                        int value = (int) (0x7fff * volume);

                        bufferlen *= 2;
                        byte[] buffer = new byte[bufferlen];
                        for (int b = 0; b < bufferlen; ) {
                                int j;
                                for (j = wavelen / 2; j > 0; j --) {
                                        buffer[b ++] = (byte) (value >> 8);
                                        buffer[b ++] = (byte) (value & 0xff);
                                }
                                value = 0x10000 - value;
                                for (j = wavelen - wavelen / 2; j > 0; j --) {
                                        buffer[b ++] = (byte) (value >> 8);
                                        buffer[b ++] = (byte) (value & 0xff);
                                }
                                value = 0x10000 - value;
                        }

                        frames_written +=
                                output.write(buffer, 0, bufferlen) / 2;

                        reschedule(frames_current);
                }
        }

        protected void reschedule(long frames) {
                /* Send a new buffer as close to the end of the
                 * currently playing buffer as possible (aim at
                 * about half into the last frame).  */
                long delay = (frames_written - frames - MIN_BUFFER / 2) *
                        1000 / S_RATE;
                if (delay < 0)
                        delay = 0;
                tick.schedule(new audio_task(), delay);
        }
}