296 lines
9.6 KiB
Python
296 lines
9.6 KiB
Python
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#!/usr/bin/env python3
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"""
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DVB-T Digital TV Receiver using RTL-SDR and GNU Radio
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Receives DVB-T signals and outputs MPEG-TS stream to stdout.
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Usage:
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python3 dvbt_rx.py --freq 506000000 | mpv -
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python3 dvbt_rx.py --freq 506e6 --input-file recording.raw | vlc -
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"""
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import argparse
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import signal
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import sys
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import os
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from gnuradio import gr, blocks, fft, dtv
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import osmosdr
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# DVB-T parameter tables
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BANDWIDTH_MAP = {
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8: (64.0 / 7e6, dtv.BANDWIDTH_8_0_MHZ), # 9142857.14 Hz
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7: (1.0 / 8e6, dtv.BANDWIDTH_7_0_MHZ), # 8000000 Hz
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6: (7.0 / 48e6, dtv.BANDWIDTH_6_0_MHZ), # 6857142.86 Hz
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}
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TRANSMISSION_MODE_MAP = {
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'2k': (dtv.T2k, 2048, 1705),
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'8k': (dtv.T8k, 8192, 6817),
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}
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CONSTELLATION_MAP = {
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'qpsk': dtv.MOD_QPSK,
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'16qam': dtv.MOD_16QAM,
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'64qam': dtv.MOD_64QAM,
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}
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CODE_RATE_MAP = {
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'1/2': dtv.C1_2,
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'2/3': dtv.C2_3,
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'3/4': dtv.C3_4,
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'5/6': dtv.C5_6,
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'7/8': dtv.C7_8,
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}
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GUARD_INTERVAL_MAP = {
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'1/4': (dtv.GI_1_4, 4),
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'1/8': (dtv.GI_1_8, 8),
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'1/16': (dtv.GI_1_16, 16),
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'1/32': (dtv.GI_1_32, 32),
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}
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def parse_freq(s):
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"""Parse frequency string, supporting scientific notation like 506e6."""
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return int(float(s))
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class DVBTReceiver(gr.top_block):
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def __init__(self, args):
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gr.top_block.__init__(self, "DVB-T Receiver")
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# Resolve parameters
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tx_mode_enum, fft_length, active_carriers = TRANSMISSION_MODE_MAP[args.transmission_mode]
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constellation = CONSTELLATION_MAP[args.constellation]
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code_rate = CODE_RATE_MAP[args.code_rate]
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gi_enum, gi_divisor = GUARD_INTERVAL_MAP[args.guard_interval]
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cp_length = fft_length // gi_divisor
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# Sample rate from bandwidth
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# DVB-T sample rate = bandwidth * 8/7 (for 8 MHz: 64/7 MHz)
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bw_mhz = args.bandwidth
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if bw_mhz == 8:
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samp_rate = 64e6 / 7.0 # 9142857.14 Hz
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elif bw_mhz == 7:
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samp_rate = 8e6
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else:
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samp_rate = 48e6 / 7.0 # 6857142.86 Hz
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print(f"--- DVB-T Receiver ---", file=sys.stderr)
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print(f"Frequency: {args.freq / 1e6:.3f} MHz", file=sys.stderr)
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print(f"Bandwidth: {bw_mhz} MHz", file=sys.stderr)
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print(f"Sample rate: {samp_rate:.0f} Hz", file=sys.stderr)
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print(f"Mode: {args.transmission_mode} (FFT={fft_length})", file=sys.stderr)
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print(f"Constellation: {args.constellation}", file=sys.stderr)
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print(f"Code rate: {args.code_rate}", file=sys.stderr)
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print(f"Guard interval:{args.guard_interval} (CP={cp_length})", file=sys.stderr)
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print(f"", file=sys.stderr)
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# --- Source ---
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if args.input_file:
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print(f"Source: file '{args.input_file}'", file=sys.stderr)
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self.source = blocks.file_source(
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gr.sizeof_gr_complex, args.input_file, repeat=False
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)
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else:
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print(f"Source: RTL-SDR (live)", file=sys.stderr)
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self.source = osmosdr.source(args="numchan=1")
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self.source.set_sample_rate(samp_rate)
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self.source.set_center_freq(args.freq)
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self.source.set_freq_corr(args.ppm)
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self.source.set_gain_mode(True)
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self.source.set_gain(args.gain)
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self.source.set_if_gain(args.if_gain)
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self.source.set_bb_gain(0)
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actual_rate = self.source.get_sample_rate()
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if abs(actual_rate - samp_rate) > 1000:
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print(f"WARNING: Requested sample rate {samp_rate:.0f} Hz but got {actual_rate:.0f} Hz",
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file=sys.stderr)
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print(f"WARNING: RTL-SDR max is ~2.4 Msps. DVB-T {bw_mhz}MHz needs {samp_rate:.0f} Hz.",
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file=sys.stderr)
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print(f"WARNING: Signal decoding will likely fail. Use --input-file for testing.",
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file=sys.stderr)
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# --- OFDM Demodulation Chain ---
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# Stream -> Vector for OFDM processing
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self.s2v_ofdm = blocks.stream_to_vector(gr.sizeof_gr_complex, fft_length)
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# OFDM symbol acquisition (timing sync, CP removal)
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self.ofdm_acq = dtv.dvbt_ofdm_sym_acquisition(
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blocks=1,
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fft_length=fft_length,
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occupied_tones=active_carriers,
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cp_length=cp_length,
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snr=100.0
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)
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# FFT: time domain -> frequency domain
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self.fft = fft.fft_vcc(
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fft_size=fft_length,
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forward=True,
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window=[],
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shift=False
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)
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# Channel estimation and equalization using reference signals
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self.demod_ref = dtv.dvbt_demod_reference_signals(
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itemsize=gr.sizeof_gr_complex,
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ninput=fft_length,
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noutput=active_carriers,
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constellation=constellation,
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hierarchy=dtv.NH,
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code_rate_HP=code_rate,
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code_rate_LP=dtv.C1_2,
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guard_interval=gi_enum,
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transmission_mode=tx_mode_enum,
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include_cell_id=0,
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cell_id=0
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)
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# --- Demapping and Decoding Chain ---
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# Vector -> Stream for demapper
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self.v2s_demod = blocks.vector_to_stream(gr.sizeof_gr_complex, active_carriers)
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# Constellation demapping (soft decision)
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self.demap = dtv.dvbt_demap(
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nsize=active_carriers,
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constellation=constellation,
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hierarchy=dtv.NH,
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transmission=tx_mode_enum,
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gain=1.0
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)
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# Bit-level inner deinterleaver
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self.bit_deintlv = dtv.dvbt_bit_inner_deinterleaver(
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nsize=active_carriers,
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constellation=constellation,
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hierarchy=dtv.NH,
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transmission=tx_mode_enum
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)
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# Viterbi decoder (inner FEC)
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self.viterbi = dtv.dvbt_viterbi_decoder(
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constellation=constellation,
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hierarchy=dtv.NH,
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coderate=code_rate,
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bsize=active_carriers
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)
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# Byte-level convolutional deinterleaver
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self.conv_deintlv = dtv.dvbt_convolutional_deinterleaver(
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nsize=136,
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I=12,
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M=17
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)
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# Reed-Solomon decoder (outer FEC) - RS(204,188,t=8) shortened from RS(255,239)
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self.rs_dec = dtv.dvbt_reed_solomon_dec(
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p=2,
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m=8,
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gfpoly=0x11d,
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n=255,
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k=239,
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t=8,
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s=51,
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blocks=8
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)
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# Energy descrambler - restores MPEG-TS sync bytes
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self.descramble = dtv.dvbt_energy_descramble(nblocks=8)
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# --- Output: MPEG-TS to stdout ---
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self.sink = blocks.file_descriptor_sink(gr.sizeof_char, 1) # fd=1 = stdout
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# --- Wire the flowgraph ---
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self.connect(
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self.source,
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self.s2v_ofdm,
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self.ofdm_acq,
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self.fft,
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self.demod_ref,
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self.v2s_demod,
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self.demap,
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self.bit_deintlv,
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self.viterbi,
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self.conv_deintlv,
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self.rs_dec,
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self.descramble,
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self.sink
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)
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print("Flowgraph built. Starting...", file=sys.stderr)
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def main():
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parser = argparse.ArgumentParser(
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description='DVB-T Digital TV Receiver',
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formatter_class=argparse.RawDescriptionHelpFormatter,
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epilog="""
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Examples:
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Live reception (requires SDR with sufficient sample rate):
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python3 dvbt_rx.py --freq 506000000 | mpv -
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From recorded IQ file:
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python3 dvbt_rx.py --freq 506e6 --input-file recording.cf32 | vlc -
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Record IQ samples first (if you have a capable SDR):
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rtl_sdr -f 506000000 -s 9142857 -g 40 recording.raw
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"""
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)
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parser.add_argument('--freq', type=parse_freq, required=True,
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help='Center frequency in Hz (e.g., 506000000 or 506e6)')
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parser.add_argument('--bandwidth', type=int, default=8, choices=[6, 7, 8],
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help='Channel bandwidth in MHz (default: 8)')
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parser.add_argument('--transmission-mode', default='8k', choices=['2k', '8k'],
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help='Transmission mode (default: 8k)')
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parser.add_argument('--constellation', default='64qam',
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choices=['qpsk', '16qam', '64qam'],
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help='Constellation (default: 64qam)')
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parser.add_argument('--code-rate', default='2/3',
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choices=['1/2', '2/3', '3/4', '5/6', '7/8'],
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help='Code rate (default: 2/3)')
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parser.add_argument('--guard-interval', default='1/32',
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choices=['1/4', '1/8', '1/16', '1/32'],
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help='Guard interval (default: 1/32)')
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parser.add_argument('--gain', type=float, default=40.0,
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help='RF gain in dB (default: 40)')
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parser.add_argument('--if-gain', type=float, default=40.0,
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help='IF gain in dB (default: 40)')
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parser.add_argument('--ppm', type=float, default=0.0,
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help='Frequency correction in PPM (default: 0)')
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parser.add_argument('--input-file', type=str, default=None,
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help='Read IQ from file instead of RTL-SDR (complex float32)')
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args = parser.parse_args()
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# Make stdout binary for MPEG-TS output
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if hasattr(sys.stdout, 'buffer'):
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sys.stdout = sys.stdout.buffer
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tb = DVBTReceiver(args)
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def signal_handler(sig, frame):
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print("\nStopping...", file=sys.stderr)
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tb.stop()
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tb.wait()
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sys.exit(0)
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signal.signal(signal.SIGINT, signal_handler)
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signal.signal(signal.SIGPIPE, signal.SIG_DFL)
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tb.start()
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try:
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tb.wait()
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except KeyboardInterrupt:
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tb.stop()
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tb.wait()
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if __name__ == '__main__':
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main()
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