[Discuss-gnuradio] atsc_cpll *almost* works

[Charles Swiger]

After converting atsc_fpll to handle complex input (to eliminate one
upconverter) it almost works, only the video out has problems.

The problem starts when this:

  float I = input.real() * a_sin;
  float Q = input.real() * a_cos;

is changed to this:

  gr_complex IQ = input * gr_complex(a_cos,-a_sin);

which would be necessary to handle negative frequencies I think.
Everything else checks out ok, I even tried using gr_sincos.h in place
of gr_nco.h like in gr_pll_carriertracking_cc and it behaves exectly the
same.


Working:

  gr_complex input = agc.scale(in[k]);
  gr_sincosf(d_phase,&a_sin,&a_cos);

  float I = input.real() * a_sin;
  float Q = input.real() * a_cos;

  out[k] = I;
  gr_complex filtered_IQ = afc.filter(gr_complex(I,Q));
  float x = phase_detector(filtered_IQ,0);
  static const float alpha = 0.001;
  static const float beta = alpha * alpha / 4;
  d_freq = d_freq + beta * x;
  d_phase = mod_2pi(d_phase + d_freq + alpha * x);


mpeg_packet_error_rate.py: 485526 errors out of 2165316 packets. 1679790
good packets. Error rate = 0.224

Almost working:

  gr_complex input = agc.scale(in[k]);
  gr_sincosf(d_phase,&a_sin,&a_cos);

  gr_complex IQ = input * gr_complex(a_cos,-a_sin);

  out[k] = IQ.real();
  gr_complex filtered_IQ = afc.filter(gr_complex(I,Q));
  float x = phase_detector(filtered_IQ,0);
  static const float alpha = 0.001;
  static const float beta = alpha * alpha / 4;
  d_freq = d_freq + beta * x;
  d_phase = mod_2pi(d_phase + d_freq + alpha * x);

mpeg_packet_error_rate.py: 258539 errors out of 2165280 packets. 1906741
good packets. Error rate = 0.119

Looks like a 36 missing packets, even tho the error rate is less, as the
video is certainly worse in mplayer.

--Chuck