Re: Gnuradio: SineWave generator python block choppy audio out

[Marcus Müller]

Hi Mitja!

Great to have you here :)


Couple of things up front:

1. This is GNU Radio 3.7. Especially if you want to implement things in Python 
blocks, 3.8
or later is a *must*. GNU Radio 3.7 is really just in legacy keepalive mode, 
not actively
developed. Please update to GNU Radio 3.8 or 3.9. You really should not start 
developing
for GNU Radio 3.7 in 2021!
2. WX GUI is dead. We stopped being able to support it a long time ago. Please 
use Qt GUI
instead.

All in all, please update your version of GNU Radio. In case any bugs occur, we 
won't be
able to help you with GNU Radio 3.7. GNU Radio 3.8 can be natively installed on 
almost all
modern Linux distros directly from their package managers, and on Windows, and 
OS X using
conda and other tools, without any complications.

With that out of the way, let's look at your code:

        for i in range(0, len(output_items[0])): #8192
            output_items[0][i] = np.sin(2 * np.pi * self.frequency * (i /
self.sample_rate)) * self.amplitude

No surprise the sound is choppy! You reset your i to 0 for every new call to 
work();
however, GNU Radio doesn't guarantee that work is called with number of items 
equal to a
multiple of your sine period.
So, this is a bug in your design. What you'd want is really something like

def work(self, input_items, output_items):
   # get rid of the for loop!
   startnr = self.ninputs_written(0)
   f_rel = 2 * np.pi * self.frequency / self.sample_rate
   number = len(output_items[0])
   output_items[0][:] = self.amplitude*np.sin(f_rel * np.arange(startnr, 
startnr+number))
   return number

Best regards
Marcus