#

# Copyright 2005,2006 Free Software Foundation, Inc.

# 

# This file is part of GNU Radio

# 

# GNU Radio is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 3, or (at your option)

# any later version.

# 

# GNU Radio is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

# 

# You should have received a copy of the GNU General Public License

# along with GNU Radio; see the file COPYING.  If not, write to

# the Free Software Foundation, Inc., 51 Franklin Street,

# Boston, MA 02110-1301, USA.

# 

from gnuradio import gr

from gnuradio.blks2impl.fm_emph import fm_deemph

import math

class wfm_rcv_fmdet(gr.hier_block2):

    def __init__ (self, demod_rate, audio_decimation):

        """

        Hierarchical block for demodulating a broadcast FM signal.

        The input is the downconverted complex baseband signal (gr_complex).

        The output is two streams of the demodulated audio (float) 0=Left, 1=Right.

        @param demod_rate: input sample rate of complex baseband input.

        @type demod_rate: float

        @param audio_decimation: how much to decimate demod_rate to get to audio.

        @type audio_decimation: integer

        """

        gr.hier_block2.__init__(self, "wfm_rcv_fmdet",

                                gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature

                                gr.io_signature(2, 2, gr.sizeof_float))      # Output signature

        lowfreq = -125e3

        highfreq = 125e3

        audio_rate = demod_rate / audio_decimation

        # We assign to self so that outsiders can grab the demodulator 

        # if they need to.  E.g., to plot its output.

        #

        # input: complex; output: float

        self.fm_demod = gr.fmdet_cf (demod_rate, lowfreq, highfreq, 0.05)

        # input: float; output: float

        self.deemph_Left  = fm_deemph (audio_rate)

        self.deemph_Right = fm_deemph (audio_rate)

        # compute FIR filter taps for audio filter

        width_of_transition_band = audio_rate / 32

        audio_coeffs = gr.firdes.low_pass (1.0 ,         # gain

                                           demod_rate,      # sampling rate

                                           15000 ,

                                           width_of_transition_band,

                                           gr.firdes.WIN_HAMMING)

        # input: float; output: float

        self.audio_filter = gr.fir_filter_fff (audio_decimation, audio_coeffs)

        if 1:

            # Pick off the stereo carrier/2 with this filter. It attenuated 10 dB so apply 10 dB gain

            # We pick off the negative frequency half because we want to base band by it!

            ##  NOTE  THIS WAS HACKED TO OFFSET INSERTION LOSS DUE TO DEEMPHASIS

            stereo_carrier_filter_coeffs = gr.firdes.complex_band_pass(10.0,

                                                                   demod_rate,

                                                                   -19020,

                                                                   -18980,

                                                                   width_of_transition_band,

                                                                   gr.firdes.WIN_HAMMING)

            #print "len stereo carrier filter = ",len(stereo_carrier_filter_coeffs)

            #print "stereo carrier filter ", stereo_carrier_filter_coeffs

            #print "width of transition band = ",width_of_transition_band, " audio rate = ", audio_rate

            # Pick off the double side band suppressed carrier Left-Right audio. It is attenuated 10 dB so apply 10 dB gain

            stereo_dsbsc_filter_coeffs = gr.firdes.complex_band_pass(20.0,

                                                                     demod_rate,

                                                                     38000-15000/2,

                                                                     38000+15000/2,

                                                                     width_of_transition_band,

                                                                     gr.firdes.WIN_HAMMING)

            #print "len stereo dsbsc filter = ",len(stereo_dsbsc_filter_coeffs)

            #print "stereo dsbsc filter ", stereo_dsbsc_filter_coeffs

            # construct overlap add filter system from coefficients for stereo carrier

            self.stereo_carrier_filter = gr.fir_filter_fcc(audio_decimation, stereo_carrier_filter_coeffs)

            # carrier is twice the picked off carrier so arrange to do a commplex multiply

            self.stereo_carrier_generator = gr.multiply_cc();

            # Pick off the rds signal

            stereo_rds_filter_coeffs = gr.firdes.complex_band_pass(30.0,

                                                                     demod_rate,

                                                                     57000 - 1500,

                                                                     57000 + 1500,

                                                                     width_of_transition_band,

                                                                     gr.firdes.WIN_HAMMING)

            #print "len stereo dsbsc filter = ",len(stereo_dsbsc_filter_coeffs)

            #print "stereo dsbsc filter ", stereo_dsbsc_filter_coeffs

            # construct overlap add filter system from coefficients for stereo carrier

            self.rds_signal_filter = gr.fir_filter_fcc(audio_decimation, stereo_rds_filter_coeffs)

            self.rds_carrier_generator = gr.multiply_cc();

            self.rds_signal_generator = gr.multiply_cc();

            self_rds_signal_processor = gr.null_sink(gr.sizeof_gr_complex);

            alpha = 5 * 0.25 * math.pi / (audio_rate)

            beta = alpha * alpha / 4.0

            max_freq = -2.0*math.pi*18990/audio_rate;

            min_freq = -2.0*math.pi*19010/audio_rate;

            self.stereo_carrier_pll_recovery = gr.pll_refout_cc(alpha,beta,max_freq,min_freq);

            #self.stereo_carrier_pll_recovery.squelch_enable(False) #pll_refout does not have squelch yet, so disabled for now 

            # set up mixer (multiplier) to get the L-R signal at baseband

            self.stereo_basebander = gr.multiply_cc();

            # pick off the real component of the basebanded L-R signal.  The imaginary SHOULD be zero

            self.LmR_real = gr.complex_to_real();

            self.Make_Left = gr.add_ff();

            self.Make_Right = gr.sub_ff();

            self.stereo_dsbsc_filter = gr.fir_filter_fcc(audio_decimation, stereo_dsbsc_filter_coeffs)

        if 1:

            # send the real signal to complex filter to pick off the carrier and then to one side of a multiplier

            self.connect (self, self.fm_demod,self.stereo_carrier_filter,self.stereo_carrier_pll_recovery, (self.stereo_carrier_generator,0))

            # send the already filtered carrier to the otherside of the carrier

            self.connect (self.stereo_carrier_pll_recovery, (self.stereo_carrier_generator,1))

            # the resulting signal from this multiplier is the carrier with correct phase but at -38000 Hz.

            # send the new carrier to one side of the mixer (multiplier)

            self.connect (self.stereo_carrier_generator, (self.stereo_basebander,0))

            # send the demphasized audio to the DSBSC pick off filter,  the complex

            # DSBSC signal at +38000 Hz is sent to the other side of the mixer/multiplier

            self.connect (self.fm_demod,self.stereo_dsbsc_filter, (self.stereo_basebander,1))

            # the result is BASEBANDED DSBSC with phase zero!

            # Pick off the real part since the imaginary is theoretically zero and then to one side of a summer

            self.connect (self.stereo_basebander, self.LmR_real, (self.Make_Left,0))

            #take the same real part of the DSBSC baseband signal and send it to negative side of a subtracter

            self.connect (self.LmR_real,(self.Make_Right,1))

            # Make rds carrier by taking the squared pilot tone and multiplying by pilot tone

            self.connect (self.stereo_basebander,(self.rds_carrier_generator,0))

            self.connect (self.stereo_carrier_pll_recovery,(self.rds_carrier_generator,1)) 

            # take signal, filter off rds,  send into mixer 0 channel

            self.connect (self.fm_demod,self.rds_signal_filter,(self.rds_signal_generator,0))

            # take rds_carrier_generator output and send into mixer 1 channel

            self.connect (self.rds_carrier_generator,(self.rds_signal_generator,1))

            # send basebanded rds signal and send into "processor" which for now is a null sink

            self.connect (self.rds_signal_generator,self_rds_signal_processor)

        if 1:

            # pick off the audio, L+R that is what we used to have and send it to the summer

            self.connect(self.fm_demod, self.audio_filter, (self.Make_Left, 1))

            # take the picked off L+R audio and send it to the PLUS side of the subtractor

            self.connect(self.audio_filter,(self.Make_Right, 0))

            # The result of  Make_Left  gets    (L+R) +  (L-R) and results in 2*L

            # The result of Make_Right gets  (L+R) - (L-R) and results in 2*R

            self.connect(self.Make_Left , self.deemph_Left, (self, 0))

            self.connect(self.Make_Right, self.deemph_Right, (self, 1))

        # NOTE: mono support will require variable number of outputs in hier_block2s

        # See ticket:174 in Trac database

        #else:

        #    self.connect (self.fm_demod, self.audio_filter, self)