256-fall-2008/hw1

Homework #1: Real-time Audio, Buffers, and Waveforms

Due date: 2008.10.8 11:59:59pm (or thereabout), Wednesday.

Let's get cookin'.

Specification (part 1 of 2): Real-time Audio

• create a program that is capable of real-time audio input/output, call it something (e.g., sig-gen; creative names are always welcome)
• start with a blank C++ program
• create a minimally compilable program (e.g., something like HelloWorld):
  • if you'd like, you can start with this very basic makefile (may need to make changes)
• next, add real-time, using the RtAudio Library (version 4.0.4)
  • download it from here
  • even though it's useful to briefly look through the package, the only files you'll need are:
    • RtAudio.h (the header file for RtAudio, it contains the class definitions)
    • RtAudio.cpp (the implementation)
    • RtError.h (header containing various error handling constructs for RtAudio)
• this is similar to (but not identical to) the example we did in class (see HelloSine):
  • your program is using an updated RtAudio interface, which is different from the one we used in class, please study
  • it may be also useful to browse the RtAudio documentation, the example programs in the RtAudio distribution
  • NOTE: even though the code is nearly all there, it's infinitely more useful to actually write the code from scratch - even if you type it in line by line!
• implement the callback function to generate the expect number of samples per call for a sine wave at 440Hz
• the overall behavior when you run the program should be a continuous sine tone at 440hz...
• to quit: press ctrl-c

Specification (part 2 of 2): Waveforms

• modify your program to generate different waveforms, depending the command line flag you specify:

    sig-gen [type] [frequency] [width]
        [type]: --sine | --saw | --pulse | --noise | --impulse
        [frequency]: (a number > 0, only applicable to some signal types)
        [width]: pulse width (only applicable to some signal types)

where the flags correspond to the following signals:

• • --sine : sine wave
  • --saw : saw tooth, the width is a number between 0.0 and 1.0 the determines the shape of the wave (e.g., width=.5 should result in a triangle wave)
  • --pulse : rectangular pulse wave, the width ([0.0-1.0]) controls the pulse width (e.g., width=.5 should result in a square wave)
  • --noise : white noise
  • --impulse : impluse train
• this means that you'll also need to implement a simple command line parser, with basic error checking (e.g., what to do when invalid/irrelevant parameters are provided?)

Note

• have fun with it!!!
• comment your code!
• choose your own coding conventions - but be consistent

Deliverables

turn in all files by putting them in your Library/Web/154/hw1/ directory, and concise online documentation + readme

• 1) source code to the project (*.h, *.cpp, *.c makefile, etc.)
• 2) online page for your project (should be viewable at http://ccrma.stanford.edu/~YOURID/154/hw1/). It should include:
  • links to your files of various kinds
  • instructions on building the project (for example, anyone in the class should be able to download
  • a short README text section that:
    • conveys your ideas/comments in constructing each program
    • describes any difficulties you encountered in the process
• 3) email Ge with the link to your web page, as a confirmation that you are turning the homework in