| 28 | } |
| 29 | |
| 30 | bool FluxDecoder::readBit() |
| 31 | { |
| 32 | if (_leading_zeroes > 0) |
| 33 | { |
| 34 | _leading_zeroes--; |
| 35 | return false; |
| 36 | } |
| 37 | else if (_leading_zeroes == 0) |
| 38 | { |
| 39 | _leading_zeroes--; |
| 40 | return true; |
| 41 | } |
| 42 | |
| 43 | while (!_fmr->eof() && (_flux < (_clock / 2))) |
| 44 | { |
| 45 | _flux += nextFlux() * _flux_scale; |
| 46 | ; |
| 47 | _clocked_zeroes = 0; |
| 48 | } |
| 49 | |
| 50 | _flux -= _clock; |
| 51 | if (_flux >= (_clock / 2)) |
| 52 | { |
| 53 | _clocked_zeroes++; |
| 54 | _goodbits++; |
| 55 | return false; |
| 56 | } |
| 57 | |
| 58 | /* PLL adjustment: change the clock frequency according to the phase |
| 59 | * mismatch */ |
| 60 | if (_clocked_zeroes <= 3) |
| 61 | { |
| 62 | /* In sync: adjust base clock */ |
| 63 | |
| 64 | _clock += _flux * _pll_adjust; |
| 65 | } |
| 66 | else |
| 67 | { |
| 68 | /* Out of sync: adjust the base clock back towards the centre */ |
| 69 | |
| 70 | _clock += (_clock_centre - _clock) * _pll_adjust; |
| 71 | |
| 72 | /* We require 256 good bits before reporting another sync loss event. */ |
| 73 | |
| 74 | if (_goodbits >= 256) |
| 75 | _sync_lost = true; |
| 76 | _goodbits = 0; |
| 77 | } |
| 78 | |
| 79 | /* Clamp the clock's adjustment range. */ |
| 80 | |
| 81 | _clock = std::min(std::max(_clock_min, _clock), _clock_max); |
| 82 | |
| 83 | /* I'm not sure what this does, but the original comment is: |
| 84 | * Authentic PLL: Do not snap the timing window to each flux transition |
| 85 | */ |
| 86 | |
| 87 | _flux = _flux * (1.0 - _pll_phase); |