Potentiometer video control

1_README.md

This is code used to control the playback speed of a video playing in Quicktime Player. Upload arduino_read_potentiometer.cpp on your Arduino and run processing_control_video.pde in Processing. See video demo at http://www.youtube.com/watch?v=UfDRINiV4Kg

2_arduino_read_potentiometer.cpp

/*
 * Potentiometer Passing
 * by Ryan Greenberg
 * 23 September 2009
 * 
 * This program gets the value of two potentiometers connected to analog inputs
 * and writes their values to serial for Processing to receive. These pots
 * control video playback speed and volume. A blinking LED matches the
 * tempo and volume of the video.
 */

int ledPin = 10;   // select the output pin for LED
int spdPin = 2;    // select the input pin for the speed pot
int volPin = 3;    // select the input pin for the volume pot
int spd = 0;       // variable to store the speed value coming from the pot
int vol = 0;       // variable to store the volume value coming from the pot
int bpm = 194; // Speed of song in beats per minute, at 100% speed
               // Calculate the BPM of a song manually at 
               // http://www.all8.com/tools/bpm.htm

float beatPeriod; // ms to wait between flashes
float beatMultiplier = 1.0; // number from -1 to 3 to multiply base bpm
long nextBeat; // time of next flash toggle
int beatOn = 0;

int pollPeriod = 1000; // ms to wait between polls
long nextPoll; // time of next poll

void setup() {
  pinMode(ledPin, OUTPUT);  // declare the ledPin as an OUTPUT
  nextPoll = millis() + pollPeriod;
  nextBeat = millis() + beatPeriod;
  setBeatPeriod();
  Serial.begin(9600);
}

void loop() {
  // Flash light to the beat
  if (millis() >= nextBeat) {
    toggleBeat();
  }
  
  // Read changes to the beat
  if (millis() >= nextPoll) {
    pollPot();
  }
}

void toggleBeat() {
  nextBeat = millis() + beatPeriod;
  if (beatOn == 1) {
    digitalWrite(ledPin, LOW);  // turn the ledPin off
    beatOn = 0;
  } else {
    analogWrite(ledPin, vol / 1024.0 * 255);
    //    digitalWrite(ledPin, HIGH);  // turn the ledPin on
    beatOn = 1;
  }
}

// An unfortunately named function
void pollPot() {
  nextPoll = millis() + pollPeriod; // set time for next reading
  spd = analogRead(spdPin);    // read the speed
  vol = analogRead(volPin);    // read the volume
  Serial.print("S"); // Send value to Processing
  Serial.println(spd);
  Serial.print("V");
  Serial.println(vol);
  beatMultiplier = spd/1023.0 * 4 - 1;
  setBeatPeriod();
}

// Calculate the flash period from the bpm frequency
void setBeatPeriod(){
  float oldBeatPeriod = beatPeriod;
    // Avoid divide by zero error
    if (beatMultiplier == 0) {
      beatPeriod = 1000000; // Big enough
    } else { 
      beatPeriod = abs((1.0 / (bpm * 2 * beatMultiplier / 60.0) * 1000));
    }
    nextBeat = nextBeat - oldBeatPeriod + beatPeriod;
}

3_processing_control_video.pde

/*
 * Arduino Movie Player
 * ---------------------- 
 *
 * Receives speed and volume values over the serial port,
 * terminated with a carriage return (ascii 13) then newline (10).
 * 
 * This matches what Arduino's " Serial.println(val)" function
 * puts out.
 *
 * Created 25 October 2006
 * copyleft 2006 Tod E. Kurt <[email protected]
 * http://todbot.com/ 
 *
 * Modified 21 September 2009 by Ryan Greenberg
 *
 */
import processing.serial.*;
import com.apple.cocoa.foundation.*; // Only works on OS X with the proper libraries installed
//import processing.video.*; // Too slow

// Change this to the portname your Arduino board
String portname = "/dev/tty.usbserial-A7006RZH"; // or "COM5"
Serial port;
String buf="";
int cr = 13;  // ASCII return   == 13
int lf = 10;  // ASCII linefeed == 10
int potVal;
int count = 0;
int col = 255;
float currentPlaySpeed = 1.0;
float currentVolume = 1.0;
//Movie myMovie;

void setup() {
  port = new Serial(this, portname, 9600);
  setupMovie();
  size(100,100);
}

void keyPressed() {
  if(key == ' ') {
    background(255,0,0);  // erase screen
  }
}

void setupMovie() {
  println("Setting up movie...");
  // Play currently open movie in QuickTime Player
  String script = "tell application \"QuickTime Player\" to play first document";
  executeScript(script);
  setVolume(7); // Start with volume turned all the way up
  delay(1500); // Wait for movie to start playing
}

void draw() {
  // Offer some visual feedback of the current pot value
  // Mostly for debugging
  background(col);
}

void setMovieSpeed(float s) {
    float diff = abs(currentPlaySpeed - s);
  println("Current: " + currentPlaySpeed + "  Requested: " + s + "  Diff: " + diff);

  if (diff < .15) {
    println("Not changing speed because change is insignificant");
  } else {
    println("Changing speed to " + s);
  String script = "tell application \"QuickTime Player\" to set rate of first document to " + s;
    executeScript(script);
    currentPlaySpeed = s;
  }
}

void setVolume(float v) {
    float diff = abs(currentVolume - v);
  println("Current: " + currentVolume + "  Requested: " + v + "  Diff: " + diff);

  if (diff < .15) {
    println("Not changing volume because change is insignificant");
   } else {
    String script = "tell application \"Finder\" to set volume " + v;
    executeScript(script);
    currentVolume = v;
  }
}

// called whenever serial data arrives
void serialEvent(Serial p) {
  int c = port.read();
  
  // Add string to buffer if not end of line
  if (c != lf && c != cr) {
    buf += char(c);
  }
  if (c == lf) {
    if (buf.charAt(0) == 'S') {
      println("Got value for speed...");
          int val = int(buf.substring(1));
          float playSpeed = (val / 1023.0 * 4.0)-1;
        setMovieSpeed(playSpeed);
        col = (int)(val / 1023.0 * 255);
    } else if (buf.charAt(0) == 'V') {
      println("Got value for volume...");
      int val = int(buf.substring(1));
      float volume = (val / 1023.0 * 7);
      setVolume(volume);
      println("Setting volume to " + val);
    }

    buf = ""; // Clear buffer
  }
}

// Used to run AppleScript
// Only works on MacOS computers
void executeScript(String script) {
  NSAppleScript myScript = new NSAppleScript(script);
  NSMutableDictionary errors = new NSMutableDictionary();
  myScript.execute(errors);  
}