Mac Forum / Programming / Mac Programming / October 2005

In article <3s7nd5Fn0419U1@individual.net>,
Pete Verdon <usenet@verdonet.organisation.unitedkingdom.invalid>
wrote:

You should download 'Noise' from <http://www.blackholemedia.com/noise/>
It does the pink noise part, and ships with source code. It's license
contains the following:

   English non-authoritative interpretation of the license:

   This is pretty much the BSD license. This means you can take the
   source and do whatever you please with it. While it isnot a
   requirement of the license, we would appreciate a mention in the
   credits of your application if you use our source.

I think that is too much 80's thinking. Nowadays, simple sound playing
means making a call 'play this sound', where the system finds out
whether a sound is .wav, .MP3, or whatever.

You may be able to generate a sine or square wave using MIDI output, but
that will be just as simple (or hard) as generating a piano sound.

Reinder

It's true, it is complicated. No simple Cocoa class for generating sine
waves (or recording audio for that matter). Alas.

yes. I used SineWave to 'learn' how I could use CoreAudio, it seems to
be one of the few resources. CoreAudio is probably a great technical
achievement, but programming it is a bear. It's a procedural
programmer's dream. Part of the problem seems to be the utter
'nerdiness' of the programmers responsable. If you've ever whitnessed an
audio related talk at WWDC you know what I mean. I didn't understand a
word of it. Also, good introductory texts are hard to find /
non-existant.

So the learning curve is steep, but it will work in the end. Mind you,
the 'Objective-C style' in that particular project is rather
non-standard, so beware.

patrick

just spotted this:
   <http://www.blackholemedia.com/noise/>

have not tried it myself, but it includes the source.

patrick

Nah.

Yeah, but it's easy.  I assume you already know how a sound waveform
works, so you already know where pi figures in.

NSSound can play AIFF data, and the AIFF format is very straightforward.
 Here's a simple sine wave tone generator I threw together.  It expects
one parameter (a frequency) on the command line.  Try, say, 500.

-Peter

#include <Cocoa/Cocoa.h>

int main(int argc, char* argv[]) {
    double frequency = strtod(argv[1], NULL);
   
    struct Simple_AIFF_File {
        /* FORM chunk */
        unsigned int formID;
        int formChunkSize;
        unsigned int formType;
       
        /* COMM chunk */
        unsigned int commID;
        int commChunkSize;
        short numChannels;
        unsigned int numSampleFrames;
        short sampleSize;
        extended80 sampleRate;
       
        /* SSND chunk */
        unsigned int ssndID;
        int ssndChunkSize;
        unsigned int offset;
        unsigned int blockSize;
        int soundData[];
    } __attribute__ ((__packed__));
   
   
    const unsigned int sampleRate = 48000;
    const unsigned int channels = 1;
    const unsigned int bytesPerFrame = channels * sizeof(unsigned int);
    const unsigned int seconds = 4;
   
    const unsigned int dataSize = seconds * sampleRate * channels *
bytesPerFrame;
    const unsigned int totalSize = dataSize + sizeof(struct Simple_AIFF_File);
   
    unsigned int i;
   
    struct Simple_AIFF_File* aiff = malloc(totalSize);
    if (! aiff) {
        printf("Out of memory allocating %lu bytes!\n", totalSize);
        return EXIT_FAILURE;
    }
   
    aiff->formID = 'FORM';
    aiff->formChunkSize = totalSize - offsetof(struct Simple_AIFF_File,
formType);
    aiff->formType = 'AIFF';
   
    aiff->commID = 'COMM';
    aiff->commChunkSize = 18;
    aiff->numChannels = 1;
    aiff->numSampleFrames = seconds * sampleRate;
    aiff->sampleSize = 32;
   
    double sampleRateDouble = (double)sampleRate;
    dtox80(&sampleRateDouble, &aiff->sampleRate);
       
    aiff->ssndID = 'SSND';
    aiff->ssndChunkSize = dataSize + 8;
    aiff->offset = 0;
    aiff->blockSize = 0;
   
    for (i=0; i < seconds * sampleRate * channels; i++) {
        aiff->soundData[i] = INT_MAX * sin(i * M_PI * 2. * (frequency /
(double)sampleRate) );
    }
   
    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
    NSData* data = [[NSData alloc] initWithBytesNoCopy:aiff length:totalSize];
       
    NSSound* sound = [[NSSound alloc] initWithData:data];
    [data release];
   
    [sound play];
    sleep(seconds);
   
    [sound release];
    [pool release];

    return 0;
}

There are some higher-level music/sound libraries available, which may
have classes of the sort you're looking for (i haven't spent much time
with them myself):

http://musickit.sourceforge.net/   (probably your best bet)

http://supercollider.sourceforge.net/  (requires you to run a
supercollider daemon in addition to your program, but i'm pretty sure
it gives you functions like brownian/pink noise, simple tone
generators, etc.)