IC 210 Fall 2010

Programming Project 1

Let’s Make Sweet Sweet Music! 


Executive Summary

Sound is produced when a pressure wave moves through a medium, usually air.  Music is an art form whose medium is sound organized in time. Common elements of music are pitch (which governs melody and harmony), rhythm (and its associated concepts tempo, meter, and articulation).  It is this structure in pitch and tempo that makes music different from random noise.  Music to be read by musicians is typically written on sheet music.  Sheet music contains all the information (notes, their length, and the tempo) that is needed to perform the piece.

Clearly, a computer can't read a piece of sheet of music, but it can produce music; how many .mp3's do you have?  So in other words with a properly formatted file a computer can produce music.   

Due Dates and Honor  

This project will be due by the close of business on Thursday 23 September 2009.  See the course policy for details about due dates and late penalties. Again, this is a Programming Project, and it is very important that you understand and abide by the Department's policy concerning programming projects. Please view: http://www.cs.usna.edu/academics/ProgrammingPolicy.pdf   

Extra Information  

1.      Sound and wave files 

What our ears perceives as sound is simply a wave moving through the air that vibrates our eardrums.  This wave propagates by the compression and rarefaction of the atmosphere (Figure 1). This change in air density at a single point can be graphed with respect to time (Figure 2).  This change in air density over time is the data that describes any sound wave and can be encoded in a file. 

Figure 1

Figure 2

 

A file containing this air density information is called a wave file (.wav).  A .wav file contains binary data consisting of two parts: 

·      A header chunk that describes the amount of information that the file contains.

·      A data chunk that contains numbers that correspond to sound amplitudes (or air pressure) over time.  

This data chunk is exactly what is encoded on a compact disc.  The header portion is not required for CDs because the encoding options are fixed. To understand the files you will be creating, you need to understand the options for encoding a wave file.  

The header chunk contains the following pieces of information (among others):

Channels should be self-explanatory.  Sample rate and bits per channel are necessary because computers can only handle discrete numbers.  In the real world, waves are continuous but computers need to approximate to represent continuous numbers.  This is shown below. 

Figure 3

 In order to represent a continuous wave, the computer will connect a series of points that are close to the original waveform.    The red line represents the original waveform.  The black line represents the waveform played by the computer.  This example shows 4 bits per channel (24=16 levels) and a sample taken every 0.1 seconds.  This means the sample rate is 10 Hz (=1/0.1 seconds).    

For this project will use mono (1 channel) 8-bit encoding at a sample rate of 8000 Hz.  In other words, our data file will be composed of 8000 discrete values for every second of sound produced. 

2. Useful data

 A basic sine wave is described by the following formula:

            y(t) = Amplitude * sin (2 * π * frequency(Hz) * time(sec))

In music, sounds are represented by notes.  Each note is a letter, C, D, E, F, G, A, and B.  Each of these notes represents a sine wave of a specific frequency.  For example the "middle C" has a frequency of 261.63 Hz.  The table below shows the frequencies of the other notes. 

Note Frequency (Hz)
C (Middle C) 261.63
D 293.66
E 329.63
F 349.23
G 392.00
A 440.00
B 493.88
Table 1 Musical Note Frequencies

On sheet music the vertical position of the note symbol tells the musician what note (frequency) to play.

Note that Middle C is actually on an imaginary line below the clef shown above. 

Clearly the chart above is not a complete list of all the notes and their frequencies, but this will work for our purposes.  If you want to add greater functionality to your program, a more complete listing of notes and their respective frequencies can be found at the following website, http://www.phy.mtu.edu/~suits/notefreqs.html 

Once you know what note to play, the next question is, "how long should that note be played?"  This is where the actual shape of the note comes into play.  The different shapes determine how many beats each note is held for.  For example a half note is held for twice as many beats as a quarter note, and a quarter note is played for twice as many beats as an eighth note. 

"But how long is a beat," you ask?  Good question.  The tempo of a piece of music is defined with a notation on the top of the staff and is measured in beats per minute (bpm), such as 90 bpm.  If there is no notation the standard tempo of 120 bpm is assumed. 

Now that we know that the music is played at a specific beats per minute tempo, and the relationship between the lengths of the different notes we just have to define how many beats each note gets.  It would be natural to assume that a whole note gets played for a whole beat but it's not quite that simple.  How many beats a note is played for depends on the piece of music being played.  So where does the musician look to figure out how many beats per note?  That information is also written on the sheet music and is represented by the the two large numbers that usually written at the beginning of a line of music.  The bottom number indicates which note "gets the beat."  In other words which note is played for one beat's worth of time.  The most common notation to see is a 4, this indicates that a quarter note is played for one beat.  So from that information you know that a half note is two beats, a whole note is four beats, an eighth note is one half a beat, etc.  

Note Name Note Symbol Notation for Text File (Steps 4 & 5)
Whole Note W
Half Note H
Quarter Note Q
Eighth Note E
Sixteenth Note S
Table 2 Note Symbols and Names

 For this project you will assume a tempo of 120 beats per minute and that a quarter note "gets the beat".  So how long should a quarter note be played for? 

3. Useful code 

A Visual Studio “project” with some needed code is provided: starter.zip. Download this and unzip it somewhere (your X: drive would be ideal – if you haven’t already, set up access to that from Bancroft; see the course home page for help). Then from Visual C++, choose “Open Project/Solution” and browse to and open “Project1.sln.” 

At the top of main.cpp, to provide you helper functions to generate the sound file you will find the following include statement: 

#include "Wave.h" 

Then in main() is the following code.  Start your code after this: 

WaveFile out;                        //creates WaveFile object named out
string fileName = "frequency.wav";   //creates variable to hold wave file name
out.OpenWrite(fileName.c_str());     //links object out to file fileName
out.SetupFormat(8000,8,1);           //sampleRate = 8000 Hz
                                     //bitsPerSample = 8, channels = mono
 

Whenever you have a number y that you want to write to the wave file use the statement:

out.WriteSample(y)

y must be a continuous number between -1 and 1.  You also must output y to the screen.  This will aid your debugging, but you will only see the last few samples on the screen.  See the sample output below for an example.  

Note: if you make a statement such as

out.WriteSample(1)

you may receive a compile error regarding “ambiguous overloaded function.” This will make sense later – for now, instead always use a variable instead of a constant (such as 1) when you use WriteSample.  

Additionally, the constant PI has been provided.  You can use it just like any variable you declare, e.g.

    area = 2 * PI * radius * radius; 

Details  

The project is divided up into five steps. You are strongly encouraged to solve each step completely - including thorough testing - before you move on to the next step. Also, remember that your program’s source code must comply with the Required Style Guide in order to maximize the grade you receive on this project.  Compile your program often so you don’t end up with a snake’s nest of errors at your first compile, and occasionally save a backup copy of your program’s source code in case your sponsor’s dog eats your X drive. 

Step 1: Create a waveform from a single "Middle C" note and write it to a wave file

Write a program that creates a wave file named step1.wav with the corresponding waveform of the C note described above. Prompt the user for an amplitude between 0 and 1.  Check that the amplitude provided by the user is between 0 and 1.  If it is outside this range, set it to 0.5.  See sample output for expected values.  This waveform should have a length of 4 seconds.  Sample output is shown below. 

If your sample output looks reasonable, try playing the sound by double-clicking on the .wav file (it will be in the same directory as your .cpp file). This will run Windows Media Player or a similar player.  You should be able to hear a C note.  

Key tip #1: If your program doesn’t stop running, click on the output window, then press Ctrl-C to kill it.

Key tip #2: You MUST close Windows Media Player after you play your sound. If not, your program will crash when you try to run it next!!

Key tip #3: For the entire project, you should need no more than 75-150 lines of code (at most).  Otherwise, you’re probably not on the right track.

Key tip #4: Save a complete copy of each step when it works before you go on to the next step.

Key tip #5: If you’re not sure why your program doesn’t work, add additional “cout” statements to test the values of variables at different points in your program (or just to see how far your program is getting).

 

 

 

Step 2: Prompt the user for the note to play and write it to a wave file

Modify your program so that reads in an amplitude and a note from the user and creates a 4 second wave file named step2.wav with the corresponding waveform.  See sample output for expected values.  Check that the amplitude provided by the user is between 0 and 1.  If it is outside this range, set it to 0.5.

 

 

 

Step 3: Create a wave file that has multiple notes from the user

Modify your program so that it gets an amplitude from the user and then gets a note from the user repeatedly, writing each note for one second.  The program will quit writing notes when the user types 'X'.  The name of the wave file should be step3.wav.  Check that the amplitude is between 0 and 1.  If it is outside this range, set it to 0.5. For this and subsequent steps you no longer need to write the sine values to the screen.

 

Tip #1: This step involves getting the note from the user, setting the proper frequency, producing the sound wave for one second, and then repeating...

 

 

Step 4: Create a wave file that has multiple notes of different lengths

Change your program so that it gets the length of the note (sixteenth, eighth, quarter, half, whole) as well as the note.  Each note should play for the appropriate amount of time.  The program will quit when the user types 'X' 'X'.  The name of the wave file should be step4.wav.  For this and subsequent steps set amplitude = 1. 

 

 

 

Step 5: Read the input from a file

First, some preliminaries to enable some nice songs: 1.) Change the beats per minute to 240 (instead of 120).  2.) Add a new note type of 'c' (lowercase C) -- this indicates a high C (frequency 523.25 Hz).  3.) Add a new length type of 'T' -- this represents a "Third" note, which lasts for 1/3 as long as a Whole note.  When done, songs can now include, for instance, "Tc" which indicates a high-C "Third" note.

Now, the real work: update your program so that it gets its input from a file rather than the keyboard.  Prompt the user for the name of the input file.  Your program should open the text file and read the note information from the file, stopping when it reaches the end of the file (no more 'X' characters to indicating stopping).  The name of the output wave file should be step5.wav.  Test your program on this mystery file, song.txt.  What tune is that? The file song.txt is also included in the zip file provided.

 

 

What to submit and how it will be graded

You will only submit a solution to one of the five steps above. You will submit your solution for the highest numbered step that actually works! For example, if you had a working solution to Step 3, but only a partially completed solution to Step 4, you would submit your Step 3 solution.  

The maximum points  for a Step 1 solution, 30, for a Step 2 solution, 55, for a Step 3 solution, 75, for a Step 4 solution, 90, and for a Step 5 solution, 100 pts. How points are assigned for a particular solution is at your instructor's discretion, however, program structure, documentation, variable names, etc. will be considered along with program correctness. Important points:

·       If your program does not compile as submitted, you will receive a zero.

·       If your program does not give correct results, penalties will be substantial. If you can't get a working Step k+1 solution, submit your Step k solution instead.

·       Your program must read input and write output in the exact format specified in this project description.

·       Your program’s source code must comply with the Required Style Guide in order to maximize the grade you receive on this project 

There will be both a paper and an electronic part to your submissions. The paper submission can be handed to your instructor in class, slid under their office door, or put in their mailbox. For the purposes of any late penalties, your project is not considered submitted until your instructor receives BOTH the electronic and paper portions of your submission.

 Electronic submission: Unless otherwise specified by your instructor, electronic submission should be a single email message with title “IC210 Project 1 Submission”. Include just your main.cpp file (the other files should not be changed). If you have any questions, send a separate message with a different subject. Be certain to include the file!

 Here's what to submit  (follow instructions for one of the following):

Step 1 submission: (max 30 pts)

Paper: Submit a printout of your source code and a screen capture showing your program being run on input 0.5. You will also submit a signed copy of the project cover page (see IC210 home page).
Electronic: See above. 
 

Step 2 submission: (max 55 pts)

Paper: Submit a printout of your source code and a screen capture showing your program being run on input E and 1.5. You will also submit a signed copy of the project cover page (see IC210 home page).
Electronic: See above. 

Step 3 submission: (max 75 pts)

Paper: Submit a printout of your source code and a screen capture showing your program being run on input C D E F G A B X and 1.5.  You will also submit a signed copy of the project cover page (see IC210 home page).

Electronic: See above.  

Step 4 submission: (max 90 pts)

Paper: Submit a printout of your source code and a screen capture showing your program being run on input QE QD QC QD QE QE HE QE QD QD QE QD WC XX.  You will also submit a signed copy of the project cover page (see IC210 home page).

Electronic: See above.  

Step 5 submission: (max 100 pts)

Paper: Submit a printout of your source code, a screen capture showing your program being run on input the input file song.txt. You will also submit a signed copy of the project cover page (see IC210 home page).
Electronic: See above.  

Extra Credit: (Maximum of 10 points combined)

Refer to the following website, http://www.phy.mtu.edu/~suits/notefreqs.html, for specific frequencies of the other notes.