diff options
Diffstat (limited to 'gr-atsc/src/python/all_atsc.py')
| -rw-r--r-- | gr-atsc/src/python/all_atsc.py | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/gr-atsc/src/python/all_atsc.py b/gr-atsc/src/python/all_atsc.py new file mode 100644 index 000000000..0137839bd --- /dev/null +++ b/gr-atsc/src/python/all_atsc.py @@ -0,0 +1,140 @@ +#!/usr/bin/env /usr/bin/python +# +# Copyright 2004 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 2, 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., 59 Temple Place - Suite 330, +# Boston, MA 02111-1307, USA. +# +# This module starts the atsc processing chain taking the captured +# off-air signal created with: +# +# uhd_rx_cfile.py --samp-rate=6.4e6 +# -f <center of tv signal channel freq> +# -g <appropriate gain for best signal / noise> +# -s output shorts +# +# All this module does is multiply the sample rate by 3, from 6.4e6 to +# 19.2e6 complex samples / sec, then lowpass filter with a cutoff of 3.2MHz +# and a transition band width of .5MHz. Center of the tv channels is +# then at 0 with edges at -3.2MHz and 3.2MHz. + +from gnuradio import gr, atsc +import sys, os, math + +def graph (args): + + nargs = len(args) + if nargs == 2: + infile = args[0] + outfile = args[1] + else: + raise ValueError('usage: interp.py input_file output_file\n') + + tb = gr.top_block () + + # Convert to a from shorts to a stream of complex numbers. + srcf = gr.file_source (gr.sizeof_short,infile) + s2ss = gr.stream_to_streams(gr.sizeof_short,2) + s2f1 = gr.short_to_float() + s2f2 = gr.short_to_float() + src0 = gr.float_to_complex() + tb.connect(srcf, s2ss) + tb.connect((s2ss, 0), s2f1, (src0, 0)) + tb.connect((s2ss, 1), s2f2, (src0, 1)) + + # Low pass filter it and increase sample rate by a factor of 3. + lp_coeffs = gr.firdes.low_pass ( 3, 19.2e6, 3.2e6, .5e6, gr.firdes.WIN_HAMMING ) + lp = gr.interp_fir_filter_ccf ( 3, lp_coeffs ) + tb.connect(src0, lp) + + # Upconvert it. + duc_coeffs = gr.firdes.low_pass ( 1, 19.2e6, 9e6, 1e6, gr.firdes.WIN_HAMMING ) + duc = gr.freq_xlating_fir_filter_ccf ( 1, duc_coeffs, 5.75e6, 19.2e6 ) + # Discard the imaginary component. + c2f = gr.complex_to_float() + tb.connect(lp, duc, c2f) + + # Frequency Phase Lock Loop + input_rate = 19.2e6 + IF_freq = 5.75e6 + # 1/2 as wide because we're designing lp filter + symbol_rate = atsc.ATSC_SYMBOL_RATE/2. + NTAPS = 279 + tt = gr.firdes.root_raised_cosine (1.0, input_rate, symbol_rate, .115, NTAPS) + # heterodyne the low pass coefficients up to the specified bandpass + # center frequency. Note that when we do this, the filter bandwidth + # is effectively twice the low pass (2.69 * 2 = 5.38) and hence + # matches the diagram in the ATSC spec. + arg = 2. * math.pi * IF_freq / input_rate + t=[] + for i in range(len(tt)): + t += [tt[i] * 2. * math.cos(arg * i)] + rrc = gr.fir_filter_fff(1, t) + + fpll = atsc.fpll() + + pilot_freq = IF_freq - 3e6 + 0.31e6 + lower_edge = 6e6 - 0.31e6 + upper_edge = IF_freq - 3e6 + pilot_freq + transition_width = upper_edge - lower_edge + lp_coeffs = gr.firdes.low_pass (1.0, + input_rate, + (lower_edge + upper_edge) * 0.5, + transition_width, + gr.firdes.WIN_HAMMING); + + lp_filter = gr.fir_filter_fff (1,lp_coeffs) + + alpha = 1e-5 + iir = gr.single_pole_iir_filter_ff(alpha) + remove_dc = gr.sub_ff() + + tb.connect(c2f, fpll, lp_filter) + tb.connect(lp_filter, iir) + tb.connect(lp_filter, (remove_dc,0)) + tb.connect(iir, (remove_dc,1)) + + # Bit Timing Loop, Field Sync Checker and Equalizer + + btl = atsc.bit_timing_loop() + fsc = atsc.fs_checker() + eq = atsc.equalizer() + fsd = atsc.field_sync_demux() + + tb.connect(remove_dc, btl) + tb.connect((btl, 0),(fsc, 0),(eq, 0),(fsd, 0)) + tb.connect((btl, 1),(fsc, 1),(eq, 1),(fsd, 1)) + + # Viterbi + + viterbi = atsc.viterbi_decoder() + deinter = atsc.deinterleaver() + rs_dec = atsc.rs_decoder() + derand = atsc.derandomizer() + depad = atsc.depad() + dst = gr.file_sink(gr.sizeof_char, outfile) + tb.connect(fsd, viterbi, deinter, rs_dec, derand, depad, dst) + + dst2 = gr.file_sink(gr.sizeof_gr_complex, "atsc_complex.data") + tb.connect(src0, dst2) + + tb.run () + +if __name__ == '__main__': + graph (sys.argv[1:]) + + |