From CCRMA Wiki
Homework #1: Real-time Audio, Buffers, and Waveforms
Due date: 2009.9.30 11:59:59pm (or thereabout), Wednesday.
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)
- next, add real-time audio support, 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
- 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
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!
- 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?
- For an easy way to test the generated audio and avoid writing a full wavefile using something like Libsndfile, just write a binary output file. The Audacity audio editor can "Import Raw" audio. Select the correct format and import. To see the frequency response, you can select a portion of audio and click Analyze->Plot Spectrum
turn in all files by putting them in your Library/Web/256/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/256a/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
- lists any collaborators
- 3) email Ge with the link to your web page, as a confirmation that you are submitting the assignment