Revision as of 12:23, 23 September 2013

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

Due date: 2013.10.01 11:59:59pm, Tuesday.

Let's get cookin'.

Specification (part 1 of 3): Real-time Audio

• create a program that is capable of real-time audio input/output
• give it name (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 (will need to make changes). For a simple introduction to make files, check out this link
• next, add real-time audio support, using the RtAudio Library (version 4.0.4)
  • download it from HelloSine above OR get the most recent (and potentially different) version 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
  • it may be also useful to browse the RtAudio documentation and the example programs in the RtAudio distribution
  • NOTE: even though the code is nearly all there in the example, it's infinitely more useful to actually write the code from scratch - even if you copy/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 3): Waveforms

• modify your program to take command line arguments and generate different signals, 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, the frequency should determine the impulse train's fundamental period
• it might be a good idea to output the usage (as show above), if insufficient or incorrect parameters are given
• you'll need to implement a simple command line parser, with basic error checking (e.g., what to do when invalid/irrelevant parameters are provided?)
• you'll also need to organize your code a bit, to selectively generate the request signal

See Signal generator hints if needed.

Specification (part 3 of 3): One Ring to Modulate Them All

• Lastly, add another command line flag:
  • --input : mic/line input (make sure to enable it in the code when initializing RtAudio)
• if specified, this flag tells the program to take the mic/line input and and multiply it against the signal being generated, and output the result!

Note

• have fun with it!!!
• your code should compile and run on the CCRMA machines
• comment your code!
• choose your own coding conventions - but be consistent
• you are welcome to work together, but you must do/turn in your own work (you'll likely get more out of it this way)
• some considerations:
  • how to organize the code for the various types of signals?
  • how much error-checking and error-reporting on the command line arguments?

Testing Audio Output

Testing audio output

Deliverables

turn in all files + readme through coursework

• 1) Log into coursework and go to Dropbox.
• 2) Create a folder named hw1 and put all the files in there. The required files are:
  • source code to the project (*.h, *.cpp, *.c makefile, etc.)
  • a short README text section that:
    • instructions on building the project (for example, anyone in the class should be able to download
    • conveys your ideas/comments in constructing each program
    • describes any difficulties you encountered in the process
    • lists any collaborators