[chuck-users] wavetable synthesis

[eduard]

hello,

Checking out the code today with a fresher mind, just realised that  
the second method does work. I forgot to bitmask the last int_pos. So  
the last line that reads:
	     (snd.valueAt( (int_pos&bitmask) + 1 ) -
	     snd.valueAt(int_pos&bitmask))*(pos-int_pos) + snd.valueAt 
(int_pos) => imp.next;

Should be:
	     (snd.valueAt( (int_pos&bitmask) + 1 ) -
	     snd.valueAt(int_pos&bitmask))*(pos-int_pos) + snd.valueAt 
(int_pos&bitmask) => imp.next;

Still think method 1 should be doable... am i missing something?

thanks

eduard


On Oct 19, 2007, at 4:40 PM, eduard aylon wrote:

> Hello list,
>
> Does anyone know if there is any UGen to store waveforms in a  
> table? Thus, wavetable synthesis.
> I've come up with a few ideas, but none of them seem to work:
>
> 1. The first was to use a Gen7 together with a phasor. However, I  
> get no sound. See the following patch which I think should  
> synthesise a sine wave:
>
> 512 => int length;
> 440. => float freq;
> 1./ length => float step;
>
> float coefs[ 2*length-1];
> for( 1 => int i; i < coefs.cap() ; 2 +=> i )
> {
>     Math.sin((i-1)*2.*pi/511.) => coefs[i-1]; // value at pos
>     step => coefs[i]; // duration of value, 1 samp
> }
> Math.sin( length*2.*pi/length ) => coefs[ length - 1]; // last value
> Phasor p => Gen7 gen7 => WvOut file => dac;
> coefs => gen7.coefs;
> freq => p.freq;
> while( true )
>     1::samp => now;
>
>
> 2. The second idea was to use a sndbuf, but the results are far  
> from satisfactory. see example:
>
> //first you need to generate one period of a sine wave:
>
> SinOsc s => WvOut file => blackhole;
> "sine_period.wav" => file.wavFilename;
> 1024 => int length;
> second/samp => float sr;
> sr/length => s.freq;
> now + length::samp => time later;
> while( now < later )
>   1::samp=>now;
>
> ----- separate chuck file ----
>
> // wavetable synth part: synthesise a sine wave at any freq
>
> SndBuf snd  => blackhole;
> Impulse imp => dac;
> "sine_period.wav" => snd.read;
> snd.samples() => int length; // must be power of 2
> length - 1 => int bitmask;
> second/samp => float sr;
>
> 440. => float freq;
> freq*length/sr => float delta;
> delta $int => int int_delta;
> 0 => float pos;
> 0 => int int_pos;
> 1 => int interpolate;
> if( me.args() ) Std.atoi( me.arg(0) ) => interpolate;
> while( true )
> {
>     if( !interpolate )
>     {
>         int_delta::samp => now;
>         snd.last() => imp.next;
>         snd.pos( snd.pos()&bitmask );
>         continue;
>     }
>
>     delta + pos => pos;
>     pos $int => int_pos;
>     (snd.valueAt( (int_pos&bitmask) + 1 ) -
>      snd.valueAt(int_pos&bitmask))*(pos-int_pos) + snd.valueAt 
> (int_pos) => imp.next;
>     1::samp => now;
>
> }
>
>
> Could someone give me a hand?
>
> thanks,
>
> eduard