just stabbing in the dark in case nobody else gives a more useful
response but...
#1 - what is the format of your output? If it's low in bitcount that
could make the signal more dirty i believe (less resolution to make a
more perfect sine wave)
#2 - have you tried calculating via doubles?
#3 - what is data->amplitude... does that ever change or is it just a
one time set volume adjustment for the left and right channels?
On Tue, Apr 26, 2011 at 12:57 PM, <eu...@lavabit.com> wrote:
> Hello,
>
> I want to generate two different frequency sinewaves on LineOut -
> Left&Right. For audio IO I'm using Portaudio(Linux, PortAudio V19-devel
> (built Apr 17 2011 22:00:29)), and the callback code is:
>
> static int paCallback( const void* inBuff, void* outBuff,
> unsigned long frpBuff,
> const
> PaStreamCallbackTimeInfo* tInf,
> PaStreamCallbackFlags flags,
> void* userData )
> {
> int16_t i;
> audioData* data = (audioData*) userData;
> float* out = (float*) outBuff;
>
> /* Prevent warnings */
> (void) tInf;
> (void) flags;
>
> for( i=0; i<frpBuff; i++ )
> {
> *out++ = data->amplitude[0] * sinf( (2.0f * M_PI) *
> data->phase[0] );
> *out++ = data->amplitude[1] * sinf( (2.0f * M_PI) *
> data->phase[1] );
>
> /* Update phase, rollover at 1.0 */
> data->phase[0] += (data->frequency[0] / SAMPLE_RATE);
> if(data->phase[0] > 1.0f) data->phase[0] -= 2.0f;
> data->phase[1] += (data->frequency[1] / SAMPLE_RATE);
> if(data->phase[1] > 1.0f) data->phase[1] -= 2.0f;
> }
>
> return paContinue;
> }
>
> When I checked the output spectrum for a 10kHz frequency using baudline
> (running on another PC), I got this http://images.cjb.net/80af2.png . The
> spectrum is clean only for output frequencies below 2-3 kHz.
>
> The tone generator inside baudline gives a clean spectrum at 10 kHz:
> http://images.cjb.net/b943b.png .
>
> What method would you recommend for generating a clean sinewave at 5-12 kHz?
> I think there is a bug somewhere, because the sine is computed in float
> for each sample and should be precise enough...
>
> Thanks
>
>
>
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