CS U216 -- Algorithms and Data Structures for Engineers

Assignment 6

Due 15 June, 2005 -- no extensions!!

Assignment 6 involves modifying the music.h file submitted for Assignment 5 so that it is useful for generating waveforms that may be written to a .wav file.

I have created a music.h file which allows a sequence of pitches to be used to generate a waveform. However, your assignment is to modify the Voice class to generate the tones. The difference is as follows. A Voice consists of a sequence of Notes, not a sequence of Pitches. Notes have durations, whereas Pitches do not have durations. Thus, when the music.h file that I have provided is used to generate tones, each tone is played for a fixed time. The music.h file that you submit, however, should play a Voice, and each Note in that voice should last an amount approximately equal to the duration member field of that Note (in seconds).

Requirements:

• The submitted file should include compiler directives to protect against multiple inclusions.
• The submitted file should not include the function main().
• The submitted file should have a Clock class similar to the one provided in the example I have provided. (Lab Examples / Lab 6 / music.h).
• The Voice class should have member functions (methods) with the following signatures (in addition to any methods that you may have already added to that class) :
  • void play()
  • bool isMore()
  • int instAmplitude()
  • void nextTick()
In a previous homework, the addNote() method was added to the Voice class. That method enabled a client to add Notes in a sequence to a Voice object. The 4 methods listed above, should enable a client of a Voice object to obtain a sequence of numeric values representing a sampled waveform corresponding to the sequence of Notes which had been added. The following rules apply to the use of these functions:
• A client is required to call the play() method before calling any other method. The behavior resulting from calling this method more than once is undefined.
• A client must call isMore() at least once between each call to nextTick() and before the first call to nextTick().
• A client may call instAmplitude() only within a sequence of operations that begins with a call to isMore() and ends with a call to nextTick(). Within that sequence, instAmplitude() may be called any number of times (including 0).
• A call to play() sets a virtual clock to the start of the sequence of Notes to be "played". A call to nextTick() advances the clock by one tick. There should be 44100 ticks in one second of "Notes".
• A call to instAmplitude should return an int value between -8192 and 8192. The sequence of values returned should correspond to a waveform appropriate to the Notes recorded with addNote(). The waveform should have a frequency corresonding to the pitch given in a Note for approximately the length of time given in the duration of that Note.
• The file you submit must have a function in it called Voice makeSong(). The return value of this function must be a Voice to which a number of notes has been added. I must be able to generate a .wav file from that Voice using the 4 functions mentioned in the previous section. The Voice should have at least 30 Notes in it, the Notes must have at least 5 different pitches. The durations of the notes must be at least 0.25 seconds each, and there must be notes of at least 3 different durations. The Notes must be in the range of audible pitches and volumes. You may write makeSong() in any fashion you choose, provided it meets the specification in this paragraph.

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The lab examples web-page includes a number of files in the Lab 6 section that may be used to create .wav files.

If you copy all of the files listed in that section and compile them, the resulting program can be used to create .wav files. Copy driver.cpp into the file which has the same name as your project followed by .cpp. Copy each of the other files into a new file in your project with the same name as that which appears in the header block of that file.

When you run the program, it will prompt you for a file name. For convenience, you should end the filename in .wav. This will allow you to play the file with Windows Media Player or QuickTime. The program will write the .wav file in the current directory. You may then open "My Computer" and navigate to that directory. The .wav file should be visible. On my system, the .wav file appears with a Windows Media Player icon. On your system it may appear differently. Double clicking on the .wav file causes it to play (at least on my system).

The machines in the labs have no speakers. If you want to hear the sounds of your .wav file playing, you will need to use ear-phones.

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Last updated 10 June 2005.